Effects of rice bran and glycerin supplementation on metabolic and productive responses of beef cows

Juan Manuel Clariget Graciela Quintans Georgget Banchero Andrea Álvarez-Oxiley Oscar Bentancur Carlos Rafael López-Mazz Raquel Pérez-Clariget About the authors

ABSTRACT

Fifty-seven primiparous Angus, Hereford, and crossbred cows were used to study the effect of strategic supplementation on metabolic, productive, and reproductive responses. The experiment had two periods including four phases: prepartum supplementation (phase I; 52 days), early postpartum (phase II; 43 days), pre-mating supplementation (phase III; 21 days), and the last phase including mating, gestation, and lactation until weaning (phase IV; 103 days). Phases I and II were considered as period 1, and phases III and IV were considered as period 2. During phase I (−52±2 days before calving to birth), half of the cows received a supplement (S-), and the rest only grazed native swards (C-). For phase III (59±2 days postpartum [DPP] until mating), cows from the previous treatments (C- or S-) were sorted in two levels of pre-mating supplementation, supplemented (-S) or not supplemented (-C), resulting in four treatment combinations (CC, CS, SC, and SS). The supplement was 1 kg dry matter/cow per day of whole rice bran and 550 mL/cow per day of crude glycerin. In period 1, cows receiving prepartum supplementation increased concentration of cholesterol, glucose, and albumin and decreased concentration of non-esterified fatty acids, beta-hydroxybutyrate, and urea. This improvement in energy balance was reflected in a higher body condition score at calving. Alternatively, in period 2, pre-mating supplementation only increased cholesterol concentration. None of the supplementation periods affected the weaning weight of calves. Prepartum, but not pre-mating, supplementation increased total pregnancy rate. A short prepartum supplementation improves pregnancy rate of primiparous cows managed under extensive production systems. However, there is no additional benefit of supplementation during the pre-mating period.

Keywords:
beef cattle; grazing; native pasture; reproduction

Introduction

In extensive pastoral production systems, based on natural grassland, pregnancy rate and weaning weights are the main limitations for cow-calf operations and, within a typical herd, primiparous beef cows are usually the category most affected (Bellows et al., 1982Bellows, R. A.; Short, R. E. and Richardson, G. V. 1982. Effects of sire, age of dam and gestation feed level on dystocia and postpartum reproduction. Journal of Animal Science 55:18-27. https://doi.org/10.2527/jas1982.55118x
https://doi.org/10.2527/jas1982.55118x...
). The nutrient supply by the Rio de la Plata grasslands and, more specifically, in the Campos subregion (Berretta et al., 2000Berretta, E. J.; Risso, D. F.; Montossi, F. and Pigurina, G. 2000. Campos in Uruguay. p.377-394. In: Grassland ecophysiology and grazing ecology. Lemaire, G.; Hodgson, J.; Moraes, A.; Nabinger, C. and Carvalho, P. C. F., eds. CAB International, Wallingford, UK; Modernel et al., 2016Modernel, P.; Rossing, W. A. H.; Corbeels, M.; Dogliotti, S.; Picasso, V. and Tittonell, P. 2016. Land use change and ecosystem service provision in Pampas and Campos grasslands of southern South America. Environmental Research Letters 11:113002. https://doi.org/10.1088/1748-9326/11/11/113002
https://doi.org/10.1088/1748-9326/11/11/...
)] during winter (∼8.7 MJ of ME/kg DM and ∼90 g of crude protein/kg DM; Mieres, 2004Mieres, J. M. 2004. Guía para la alimentación de rumiantes. Serie técnica N° 142. INIA, Montevideo. 84p.) is insufficient to meet the last third of pregnancy requirements (Ferrell et al., 1976Ferrell, C. L.; Garrett, W. N. and Hinman, N. 1976. Growth development and composition of the udder and gravid uterus of beef heifers during pregnancy. Journal of Animal Science 42:1477-1489. https://doi.org/10.2527/jas1976.4261477x
https://doi.org/10.2527/jas1976.4261477x...
). The shortage of nutrients that causes a negative energy balance (NEB) during late gestation (Quintans et al., 2010Quintans, G.; Banchero, G.; Carriquiry, M.; López-Mazz, C. and Baldi, F. 2010. Effect of body condition and suckling restriction with and without presence of the calf on cow and calf performance. Animal Production Science 50:931-938. https://doi.org/10.1071/AN10021
https://doi.org/10.1071/AN10021...
; Astessiano et al., 2012Astessiano, A. L.; Pérez-Clariget, R.; Quintans, G.; Soca, P. and Carriquiry, M. 2012. Effects of a short-term increase in the nutritional plane before the mating period on metabolic and endocrine parameters, hepatic gene expression and reproduction in primiparous beef cows on grazing conditions. Journal of Animal Physiology and Animal Nutrition 96:535-544. https://doi.org/10.1111/j.1439-0396.2011.01178.x
https://doi.org/10.1111/j.1439-0396.2011...
) and early postpartum due to milk production (Short et al., 1990Short, R. E.; Bellows, R. A.; Staigmiller, R. B.; Berardinelli, J. G. and Custer, E. E. 1990. Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle. Journal of Animal Science 68:799-816. https://doi.org/10.2527/1990.683799x
https://doi.org/10.2527/1990.683799x...
; Astessiano et al., 2013Astessiano, A. L.; Pérez-Clariget, R.; Espasandín, A. C.; López-Mazz, C.; Soca, P. and Carriquiry, M. 2013. Metabolic, productive and reproductive responses to postpartum short-term supplementation in primiparous beef cows. Revista Brasileira de Zootecnia 42:246-253. https://doi.org/10.1590/S1516-35982013000400003
https://doi.org/10.1590/S1516-3598201300...
) is normally followed by a decreased reproductive outcome (Soca et al., 2013Soca, P.; Carriquiry, M.; Keisler, D. H.; Claramunt, M.; Do Carmo, M.; Olivera-Muzante, J.; Rodríguez, M. and Meikle, A. 2013. Reproductive and productive response to suckling restriction and dietary flushing in primiparous grazing beef cows. Animal Production Science 53:283-291. https://doi.org/10.1071/AN12168
https://doi.org/10.1071/AN12168...
).

The negative energy balance is evidenced by changes in the concentration of some metabolites and metabolic hormones and a decrease in body condition score (BCS) of the cows. Within the metabolites and hormones, non-esterified fatty acids (NEFA) and beta-hydroxybutyrate (BHB) are increased and cholesterol, glucose, and insulin are decreased (Wettemann et al., 2003Wettemann, R. P.; Lents, C. A.; Ciccioli, N. H.; White, F. J. and Rubio, I. 2003. Nutritional and suckling mediated anovulation in beef cows. Journal of Animal Science 81:E48-E59.; Quintans et al., 2010Quintans, G.; Banchero, G.; Carriquiry, M.; López-Mazz, C. and Baldi, F. 2010. Effect of body condition and suckling restriction with and without presence of the calf on cow and calf performance. Animal Production Science 50:931-938. https://doi.org/10.1071/AN10021
https://doi.org/10.1071/AN10021...
; Soca et al., 2014aSoca, P.; Carriquiry, M.; Claramunt, M.; Ruprechter, G. and Meikle, A. 2014a. Metabolic and endocrine profiles of primiparous beef cows grazing native grassland. 2. Effects of body condition score at calving, type of suckling restriction and flushing on plasmatic and productive parameters. Animal Production Science 54:862-868. https://doi.org/10.1071/AN13251
https://doi.org/10.1071/AN13251...
; Quintans et al., 2016Quintans, G.; Scarsi, A.; Roig, G.; Carriquiry, M. and Banchero, G. 2016. Influence of a short-term prepartum supplementation on beef cows and calves’ performance in pastoral conditions. Animal Production Science 56:1913-1919. https://doi.org/10.1071/AN15082
https://doi.org/10.1071/AN15082...
), negatively influencing follicle growth and ovulation (Wiltbank, 1970Wiltbank, J. N. 1970. Research needs in beef cattle reproduction. Journal of Animal Science 31:755-762. https://doi.org/10.2527/jas1970.314755x
https://doi.org/10.2527/jas1970.314755x...
; Sinclair et al., 2002Sinclair, K. D.; Molle, G.; Revilla, R.; Roche, J. F.; Quintans, G.; Marongiu, L.; Sanz, A.; Mackey, D. R. and Diskin, M. G. 2002. Ovulation of the first dominant follicle arising after day 21 post partum in suckling beef cows. Animal Science 75:115-126. https://doi.org/10.1017/S1357729800052899
https://doi.org/10.1017/S135772980005289...
). Cows with low BCS at calving have longer anestrus postpartum and low pregnancy rates (Wettemann et al., 2003Wettemann, R. P.; Lents, C. A.; Ciccioli, N. H.; White, F. J. and Rubio, I. 2003. Nutritional and suckling mediated anovulation in beef cows. Journal of Animal Science 81:E48-E59.; Soca et al., 2014bSoca, P.; Carriquiry, M.; Claramunt, M.; Gestido, V. and Meikle, A. 2014b. Metabolic and endocrine profiles of primiparous beef cows grazing native grassland. 1. Relationship between body condition score at calving and metabolic profiles during the transition period. Animal Production Science 54:856-861. https://doi.org/10.1071/AN13250
https://doi.org/10.1071/AN13250...
), milk production, and calf weight at weaning. This is even deeper in primiparous cows (Bellows et al., 1982Bellows, R. A.; Short, R. E. and Richardson, G. V. 1982. Effects of sire, age of dam and gestation feed level on dystocia and postpartum reproduction. Journal of Animal Science 55:18-27. https://doi.org/10.2527/jas1982.55118x
https://doi.org/10.2527/jas1982.55118x...
), since they have an additional energy demand to continue growing (Short et al., 1990Short, R. E.; Bellows, R. A.; Staigmiller, R. B.; Berardinelli, J. G. and Custer, E. E. 1990. Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle. Journal of Animal Science 68:799-816. https://doi.org/10.2527/1990.683799x
https://doi.org/10.2527/1990.683799x...
).

Short-term supplementation before calving or mating are alternatives to increase the productive and reproductive efficiency of beef cows grazing native swards (Pérez-Clariget et al., 2007Pérez-Clariget, R.; Carriquiry, M. and Soca, P. 2007. Estrategias de manejo nutricional para mejorar la reproducción en ganado bovino. Archivos Latinoamericanos de Producción Animal 15:114-119; Soca et al., 2013Soca, P.; Carriquiry, M.; Keisler, D. H.; Claramunt, M.; Do Carmo, M.; Olivera-Muzante, J.; Rodríguez, M. and Meikle, A. 2013. Reproductive and productive response to suckling restriction and dietary flushing in primiparous grazing beef cows. Animal Production Science 53:283-291. https://doi.org/10.1071/AN12168
https://doi.org/10.1071/AN12168...
; Quintans et al., 2016Quintans, G.; Scarsi, A.; Roig, G.; Carriquiry, M. and Banchero, G. 2016. Influence of a short-term prepartum supplementation on beef cows and calves’ performance in pastoral conditions. Animal Production Science 56:1913-1919. https://doi.org/10.1071/AN15082
https://doi.org/10.1071/AN15082...
). However, since traditional concentrates are relatively expensive, it is necessary to evaluate cheaper alternatives.

Crude glycerin (12.5-14.8 MJ of ME/kg DM; Schröder and Südekum, 1999Schröder, A. and Südekum, K. H. 1999. Glycerol as a by-product of biodiesel production in diets for ruminants. p.241. In: Proceedings of the 10th International Rapeseed Congress: new horizons for an old crop. Wratten, N. and Salisbury, P. A., eds. Canberra, Australia.; Donkin, 2008Donkin, S. S. 2008. Glycerol from biodiesel production: the new corn for dairy cattle. Revista Brasileira de Zootecnia 37:280-286. https://doi.org/10.1590/S1516-35982008001300032
https://doi.org/10.1590/S1516-3598200800...
) and whole rice bran (10.6-13.3 MJ of ME/kg DM and 134-181 g of crude protein/kg DM; Wang et al., 2012Wang, Y.; Xin, H. S.; Li, Y. Z.; Zhang, W. W.; Xia, K.; Wang, Z. B.; Li, M. and Zhang, Y. G. 2012. The effects of different processing methods on the estimated nutritional value of rice bran according to NRC-2001 Model or DVE/OEB System. Journal of Animal and Feed Sciences 21:503-520. https://doi.org/10.22358/jafs/66125/2012
https://doi.org/10.22358/jafs/66125/2012...
; NRC, 2016NRC - National Research Council. 2016. Nutrient requirements of beef cattle. 8th ed. California, USA.) are subproducts of the industry not used for human consumption. Notwithstanding, whole rice bran, widely used for cattle in South America to supplement poor-quality herbage (Pérez-Clariget et al., 2007Pérez-Clariget, R.; Carriquiry, M. and Soca, P. 2007. Estrategias de manejo nutricional para mejorar la reproducción en ganado bovino. Archivos Latinoamericanos de Producción Animal 15:114-119; Soca et al., 2013Soca, P.; Carriquiry, M.; Keisler, D. H.; Claramunt, M.; Do Carmo, M.; Olivera-Muzante, J.; Rodríguez, M. and Meikle, A. 2013. Reproductive and productive response to suckling restriction and dietary flushing in primiparous grazing beef cows. Animal Production Science 53:283-291. https://doi.org/10.1071/AN12168
https://doi.org/10.1071/AN12168...
), is a moderate-energy supplement that can be easily improved by adding crude glycerin. The new mix of supplements would not only have a better energetic value than rice bran alone (Clariget et al., 2016aClariget, J. M.; Pérez-Clariget, R.; Álvarez-Oxiley, A.; Bentancur, O. and Bruni, M. Á. 2016a. Suplementación con glicerina cruda y afrechillo de arroz entero a vacas de carne pastoreando campo natural. Agrociencia Uruguay 20:121-131), but will also decrease the unit price of the final supplement.

We hypothesized that a strategic supplementation with a mix of whole rice bran and crude glycerin before calving and before mating would improve the energy balance and productive and reproductive performance of beef cows grazing native swards. Our objective was to evaluate the effect of supplementation either during 52 days before calving or 21 days before mating on metabolic and hormonal profiles, BW, BCS, milk production and composition, calf weight, ovarian activity, and pregnancy rate of primiparous beef cows grazing Campos grasslands of southern South America.

Material and Methods

The experiment was conducted at Cerro Largo, Uruguay (32° S, 54° W) according to the experimental procedures approved by the institutional Animal Experimental Committee (021130-001144-12).

The experiment had four phases (Figure 1): prepartum supplementation (phase I; 52 days), early postpartum (phase II; 43 days), pre-mating supplementation (phase III; 21 days), and the last phase that included mating, gestation, and lactation until weaning (phase IV; 103 days). For statistical purposes, phases I and II were considered as period 1, and phases III and IV were considered as period 2.

Figure 1
Overall management of the cows during the experiment.

Fifty-seven Hereford (19), Aberdeen Angus (7), and crossbred (31) pregnant heifers [230±2 days of gestation and 4.8±0.1 units of BCS (scale: 1-8, in which 1 = emaciated, 8 = obese); Vizcarra et al., 1986Vizcarra, J. A.; Ibañez, W. and Orcasberro, R. 1986. Repetibilidad y reproductividad de dos escalas para estimar la condición corporal de vacas Hereford. Investigaciones Agronómicas 7:45-47)] were stratified by BCS and calving date and randomly assigned to different treatments. Treatments were: unsupplemented (CC, n = 15), supplemented only in prepartum (SC, n = 14), supplemented only in pre-mating period (CS, n = 13), and supplemented in prepartum and pre-mating periods (SS, n = 15). To achieve this, in phase I (last 52±2 days of gestation), 29 cows were supplemented (S-), and 28 cows were unsupplemented (C-). Then, in phase III at 59±2 days postpartum (DPP), cows within each previous group (S- and C-) were randomly assigned to the pre-mating supplemented group (-S, n = 28) and pre-mating unsupplemented group (-C, n = 29) for 21 days before the onset of the breeding period.

Groups S were supplemented with 1 kg DM/cow per day of whole rice bran (139 g of CP/kg DM and estimated ME of 13.2 MJ/kg DM) and 550 mL/cow per day of crude glycerin (Alcoholes del Uruguay; ALUR, Uruguay; 6 g of CP/kg DM and estimated ME of 15.4 MJ/kg DM). Supplemented cows were individually penned and allowed to consume the supplement at the same time in the morning (∼ 8.00 h).

During the whole experiment, all cows grazed together on the same sward, and fresh paddock was used in each experimental phase. During phase I, cows were offered an herbage allowance (HA) of 7.5 kg/100 kg of BW per day (2144 kg DM/ha; 70 g of CP/kg DM and ME of 6.1 MJ/kg DM) until calving. Thereafter, from phases II to IV, cows were offered an HA of 10 kg/100 kg of BW per day (2401 kg DM/ha; 110 g of CP/kg DM, and ME of 7.9 MJ/kg DM) until the end of the experiment. The selected HA (7.5 and 10 kg/100 kg of BW per day) are within the range used for this geographic region (Da Trindade et al., 2016Da Trindade, J. K.; Neves, F. P.; Pinto, C. E.; Bremm, C.; Mezzalira, J. C.; Nadin, L. B.; Genro, T. C. M.; Gonda, H. L. and Carvalho, P. C. F. 2016. Daily forage intake by cattle on natural grassland: response to forage allowance and sward structure. Rangeland Ecology & Management 69:59-67. https://doi.org/10.1016/j.rama.2015.10.002
https://doi.org/10.1016/j.rama.2015.10.0...
).

Whole rice bran and crude glycerin were mixed daily before supplementation. The mixed supplement provided 21.4 MJ of ME and 142 g of CP. Chemical composition of whole rice bran and herbage (Table 1) were evaluated [ether extract (EE; AOAC, 1990AOAC - Association of Official Analytical Chemists. 1990. Official methods of analysis. 15th ed AOAC International, Arlington, VA, USA.), ash and CP (AOAC, 2007AOAC - Association of Official Analytical Chemists. 2007. Official methods of analysis. 18th ed AOAC International, Washington, DC, USA.), neutral and acid detergent fibers (NDF and ADF; Van Soest et al., 1991Van Soest, P. J.; Robertson, J. B. and Lewis, B. A. 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. In: Symposium: Carbohydrate methodology, metabolism, and nutritional implications in dary cattle. Journal of Dairy Science 74:3583-3597. https://doi.org/10.3168/jds.S0022-0302(91)78551-2
https://doi.org/10.3168/jds.S0022-0302(9...
)], and ME values were estimated using NRC (2016). Chemical composition of crude glycerin (Table 1) was evaluated [water (AOCS, 2009AOCS - American Oil Chemists’ Society. 2009. Official methods and recommended practices. 100th ed AOCS International, Florida, USA.; Ea 8-58), ash (AOCS, 1973AOCS - American Oil Chemists’ Society. 1973. Official methods and recommended practices. 64th ed AOCS International, New Orleans, USA.: Ea 2-38), glycerol (AOCS, 2012AOCS - American Oil Chemists’ Society. 2012. Official methods and recommended practices. 103rd ed AOCS International, California, USA.; Ea 6-51), fat (AOAC, 1980AOAC - Association of Official Analytical Chemists. 1980. Official methods of analysis. 13th ed AOAC International, Washington, DC, USA.; 14.019)], and methanol concentration was analyzed.

Table 1
Chemical composition of native herbage (Campos biome) and supplements used during pre-partum and pre-mating phases of primiparous beef cows

Before pre-mating supplementation, all cows were checked for anestrus by ovarian ultrasound. Cows were determined to be in anestrus when there was non-corpus luteum in two ovarian ultrasound studies separated by nine days (Wiltbank et al., 2002Wiltbank, M. C.; Gümen, A. and Sartori, R. 2002. Physiological classification of anovulatory conditions in cattle. Theriogenology 57:21-52. https://doi.org/10.1016/S0093-691X(01)00656-2
https://doi.org/10.1016/S0093-691X(01)00...
).

Seven days after pre-mating supplementation began (66±2 DPP), all calves (n = 57) were fitted with a nose plate for 14 days. When supplementation finished, nose plates were removed from the calves, and two bulls were introduced for 74 days (80 to 154 DPP).

Pre-grazing herbage mass was determined by the double sampling method (Haydock and Shaw, 1975Haydock, K. P. and Shaw, N. H. 1975. The comparative yield method for estimating dry matter yield of pasture. Australian Journal of Experimental Agriculture and Animal Husbandry 15:663-670. https://doi.org/10.1071/EA9750663
https://doi.org/10.1071/EA9750663...
). Sward surface height was determined as described by Soca et al. (2007)Soca, P.; Claramunt, M. and Do Carmo, M. 2007. Sistemas de cría vacuna en ganadería pastoril sobre campo nativo sin subsidios: propuesta tecnológica para estabilizar la producción de terneros con intervenciones de bajo costo y de fácil implementación. Revista Ciencia Animal 3:3-22. The mean ± standard deviation of the herbage mass and sward surface height for all phases (July to December) were 2272±784 kg DM/ha and 11±2 cm, respectively. In each phase, the HA was adjusted with paddock size and BW of the animals.

The BW and BCS of cows were recorded every 14 days from the beginning of the experiment (−52±2 DPP) until the start of the pre-mating supplementation (59±2 DPP). Thereafter, BW and BCS were recorded at the beginning of temporary weaning (66±2 DPP), at the end of the pre-mating supplementation (80±2 DPP), and then one week and one month after (87±2and 117±2 DPP, respectively). Calves were weighed from birth to 117±2 days of age at the same time as cows. Weaning weight was recorded at 183±2 days of age (Figure 1).

Milk production was determined on seven occasions on two consecutive days, using a portable milk machine (DYNAMICS®, Uruguay), on 8, 25, 43, 58, 66, 87, and 117±2 DPP (Figure 1). Milking was carried out according to the method described by Mondragon et al. (1983)Mondragon, I.; Wilton, J. W.; Allen, O. B. and Song, H. 1983. Stage of lactation effects, repeatabilities and influences on weaning weights of yield and composition of milk in beef cattle. Canadian Journal of Animal Science 63:751-761 and Quintans et al. (2010)Quintans, G.; Banchero, G.; Carriquiry, M.; López-Mazz, C. and Baldi, F. 2010. Effect of body condition and suckling restriction with and without presence of the calf on cow and calf performance. Animal Production Science 50:931-938. https://doi.org/10.1071/AN10021
https://doi.org/10.1071/AN10021...
. Briefly, in the morning, cows were separated from their calves, and the udder emptied using 20 IU of oxytocin i/m (Neurofisin, Lab Fatro, Uruguay); 7 h later, cows were milked again using the same methodology and returned with their calves. The milk recovered for each cow after mechanical milking was weighed on an electronic scale (with an accuracy of ±0.1 g), and daily production was estimated. After that, a sample of milk from each cow was obtained and sent to the laboratory for chemical analysis. Milk composition (protein, fat, and lactose) was determined using absorption of infrared radiation.

From 50±2 DPP until the end of the first month of mating, ovaries were examined weekly by transrectal ultrasonography using a linear bimodal (5.0 to 7.5 MHz) transducer (Ambivision, Digital Notebook B mode, Model AV-3018V, Manufacturer AMBISEA Technology Corp., Ltd., China). Ovarian follicles and corpus luteum were identified according to the criteria described by Griffin and Ginther (1992)Griffin, P. G. and Ginther, O. J. 1992. Research applications of ultrasonic imaging in reproductive biology. Journal of Animal Science 70:953-972. https://doi.org/10.2527/1992.703953x
https://doi.org/10.2527/1992.703953x...
. The resumption of ovarian activity was determined by the presence of corpus luteum in two successive ultrasound exams.

Estrus was detected twice daily (7.00 and 19.00 h) during the first month of the mating period (Figure 1); a cow was considered in estrus after accepting being mounted by the bull (Alexander et al., 1986Alexander, G.; Signoret, J. P. and Hafez, E. S. 1986. Comportamiento sexual, materno y neonatal. p.286-289. In: Reproducción e inseminación artificial en animales. Hafez, E. S., ed. México, DF, México.). Pregnancy was diagnosed by transrectal ultrasonography at 145±2 and 181±2 DPP to determine the early and total pregnancy rates, respectively.

Weekly blood samples were taken from the coccygeal vein from the beginning of prepartum supplementation (−52 DPP) until the first two weeks of the mating period (94 DPP; Figure 1), using heparinized tubes for determinations of hormone and metabolite concentrations. Samples were centrifuged within the first hour after collection at 1,530 g for 15 min, and the plasma collected and stored at −20 °C until processing.

Insulin concentration was determined by an immunoradiometric assay (IRMA; Diasource, Brussels, Belgium). All samples were analyzed in one assay, the standard curve, and controls in duplicate and the samples in single. The sensitivity of the assay was 0.5 uIU/mL with intra-assay coefficients of variation for low (22.5 uIU/mL) and high (87.4 uIU/mL) controls of 16.1 and 9.7%, respectively. Glucose, total protein, albumin, urea, cholesterol, NEFA, and BHB concentrations were determined spectrophotometrically using commercial kits (glucose oxidase/peroxidase, biuret, bromocresol green; urease/salicylate; cholesterol oxidase/peroxidase, BioSystems SA, Barcelona, Spain; Wako NEFA-HR (2), Wako Pure Chemical Industries Ltd., Osaka, Japan; Ranbut, Randox, Northern Ireland, United Kingdom, respectively), with a sample volume and reagents adjusted to 96 cells and read in a Multiskan EX (Thermo Scientific, Waltham, Massachusetts, USA). Intra and inter-assay coefficients of variation for high and low controls were always less than 15%.

Data from BW, BCS, milk production and composition, metabolites, and hormones were analyzed using a repeated measures analysis over time using mixed models (PROC MIXED of SAS - Statistical Analysis System, version 9.4), with pre- or postpartum days as the repetition factor, and initial values as covariates. Individual cow was considered the experimental unit. Cow and calf BW, cow BCS, milk production and composition, metabolites, and hormone concentration were analyzed in two periods as described before. In period 1 (−52 DPP until the first 43 DPP), only prepartum supplementation was considered in the model; in period 2 (59 DPP until end of experiment), both prepartum and pre-mating supplementation and the interaction between them were analyzed. The first model (period 1) included the effects of treatments prepartum, pre or postpartum days, and interaction between the two factors as fixed effects and cow as a random effect. The second model (period 2) included the effects of supplementation (supplement or not supplemented), a period of supplementation (prepartum or pre-mating), date, and their interactions as fixed effects and cow as a random effect. The statistical model used for perid 1 was:

Yijk = μ + c 1 + Ti + Dj + TDij + ε ijk,

in which μ = overall mean, c1 = covariate with the initial value of the variable, Ti = effect of supplementation, Dj = effect of date, TDij = effect of interaction between supplementation and date, and εijk = residual error.

The statistical model used for period 2 was:

Yimjk = μ + c 1 + Ti + Pm + TPim + Dj + TDij + PDmj + TPDimj + ε imjk,

in which μ = overall mean; c1 = covariate with the initial value of the variable; Ti = effect of supplementation; Pm = effect of period; TPim = effect of interaction between supplementation and period; Dj = effect of date; TDij = effect of interaction between supplementation and date; PDmj = effect of interaction between period and date; TPDimj = effect of interaction among supplementation, period, and date; and εimjk = residual error.

Reproductive variables were analyzed with the second model using a generalized linear model using PROC GENMOD of SAS, with the function natural logarithm link or logit link and indicating gamma distribution (interval partum-conception) or binomial (% cycling, % early, and final pregnancy) in the model, respectively. The statistical model used was:

Yimk = μ + Ti + Pm + TPim + ε imk ,

in which μ = overall mean, Ti = effect of supplementation, Pm = effect of period, TPim = effect of interaction between supplementation and period, and εimk = residual error.

Results were presented as least square means ± pooled standard error, and differences were considered statistically significant at P≤0.05.

Results

Supplementation affected (P<0.01) BW and BCS during prepartum and early postpartum (43 DPP), but there was no interaction (P≥0.55) between supplementation and DPP. Supplemented cows were heavier (P<0.01) and had greater BCS than unsupplemented cows (S-: 396±2 kg, 4.5±0.1 units vs C-: 388±2 kg, 4.3±0.1 units, BW and BCS, respectively). All cows lost BCS (P<0.01) from day −52 until one week after calving, and remained low after 43 DPP. When BCS at calving was analyzed alone, group S- had greater (P = 0.03) BCS than cows of group C- (S-: 4.5±0.1 vs. C-: 4.1±0.1 units). Prepartum supplementation did not influence (P = 0.80) calf birth weight (S-: 35.0±0.7 vs C-: 34.7±0.7 kg), and no calving difficulties were observed.

Milk production in the first 43 DPP was not affected (P = 0.94) by prepartum supplementation (7.6±0.4 kg/day for both groups), and no interaction of supplementation by DPP was found (P = 0.99). The means of the total content of fat, protein, and lactose in milk were not different (P>0.10) between groups. No interaction between supplementation and DPP (P>0.10) was found for any of the variables studied. Regardless of the treatments, the averages of total milk production of fat, protein, and lactose for both groups were: 290±19, 229±11, 383±18 g/day, respectively.

Prepartum supplementation decreased (P<0.01) plasma concentration of NEFA (S-: 1.01±0.05 vs C-: 1.33±0.05 mmol/L) and BHB (S-: 0.54±0.03 vs C-: 0.76±0.03, mmol/L), and interactions between supplementation and DPP were found for both variables (P<0.01). During the prepartum period, group S- maintained the initial concentration of both metabolites. Meanwhile, cows in group C- increased plasma concentrations of BHB and NEFA. After parturition, these differences disappeared (Figures 2a and 2b). Alternatively, plasma concentration of cholesterol was greater (P<0.01) in S- (158.0±3.3 mg/dL) than in C- cows (132.0±3.3 mg/dL), and there was an interaction between supplementation and DPP (P<0.01). The concentration of cholesterol in S- cows increased and remained higher (P<0.05) than in C- cows until calving, while in C- cows, it did not change (P>0.10; Figure 2e).

Figure 2
Concentrations of insulin and metabolites in primiparous beef cows unsupplemented () and supplemented for 52±2 days pre-partum with whole rice bran and crude glycerin ().

Plasma concentration of total protein (S-: 73.6±1.1 vs C-: 74.4±1.1 g/L; P = 0.62) was not influenced by prepartum supplementation, and there was no interaction between supplementation and DPP (P = 0.34; Figure 2h). As a consequence of prepartum supplementation, albumin plasma concentration increased (S-: 33.0±0.5 vs C-: 31.4±0.5 g/L; P = 0.01) and urea concentration decreased (S-: 22.4±0.6 vs C-: 27.3±0.6 mg/dL; P<0.01). There was no interaction between supplementation and DPP (P = 0.30) on albumin concentration (Figure 2g). However, an interaction (P<0.01) between supplementation and DPP on urea concentration was observed. In fact, the pattern of urea concentrations was greater (P<0.05) during the last three weeks before calving in C- cows than in S- cows (Figure 2f). After calving, all these differences disappeared.

Cows in S- group had greater (P<0.01) plasma concentrations of glucose than cows in C- group (S-: 67.4±0.9 vs. C-: 62.3±0.9 mg/dL), and an interaction between supplementation and DPP (P = 0.01) was found (Figure 2c). However, no effect of supplementation (P = 0.15) or interaction between supplementation and DPP (P = 0.38; Figure 2d) influenced plasma concentration of insulin.

At the beginning of pre-mating supplementation, all cows were on average 59±2 DPP, their BW and BCS were 383±3 kg and 4.2±0.1, respectively, and they were all in anestrus.

During pre-mating and mating periods (59 to 117±2 DPP), prepartum, pre-mating supplementation, or their interaction did not influence (P>0.09) BW or BCS (Table 2). Pre-mating supplemented cows produced 8.5% more milk than unsupplemented cows (-S: 6.5±0.3 vs -C: 6.0±0.3 kg/day), but these differences were not significant (P = 0.06). No effects of prepartum or pre-mating supplementation or their interaction were found (P>0.06) on milk total content of lactose, fat, and protein. Weight of calves from 59 to 117±2 days of age was not influenced by any of the supplementation periods or their interaction (P>0.10); therefore, BW of calves at weaning was not affected by treatments (P>0.10; Table 2).

Table 2
Productive, metabolic, and reproductive performance of primiparous beef cows unsupplemented (C-) or supplemented with whole rice bran and crude glycerin (S-) for 52 days pre-partum and unsupplemented (-C) or supplemented with whole rice bran and crude glycerin (-S) for 21 days pre-mating

Albumin concentration during the second experimental period was greater (P<0.01) for prepartum supplemented cows (31.5±0.5 g/L) than for non-prepartum supplemented cows (29.6±0.5 g/L). Meanwhile, pre-mating supplementation increased (P = 0.04) plasma cholesterol concentration (-S: 162±4 vs. -C: 149±4 mg/dL; Table 2).

No interaction of prepartum supplementation and date was observed for any of the variables studied during pre-mating and mating periods. On the contrary, interaction of pre-mating supplementation and date affected plasma concentration of BHB (P = 0.01), NEFA (P<0.01), and insulin (P = 0.01). Indeed, -S cows maintained (P>0.1) plasma concentration of NEFA, increased (P<0.05) plasma concentration of insulin, and decreased (P<0.05) concentrations of BHB in relation to -C cows (Figure 3).

Figure 3
Concentrations of BHB, NEFA, insulin, and urea in primiparous beef cows unsupplemented () and supplemented for 21 days pre-mating with whole rice bran and crude glycerin ().

There was only a triple interaction amongst prepartum, pre-mating supplementation, and DPP (P = 0.03) on plasma concentration of cholesterol. Cows supplemented in both periods had the greatest (P<0.05) plasma concentration of cholesterol at 80±2 DPP (CC: 156.8±9.6; CS: 156.5±10.3; SC: 153.7±10.0 and SS: 201.0±10.4 mg/dL).

No interaction (P>0.10) between prepartum and pre-mating supplementation on reproductive variables was found. Prepartum supplementation did not increase the percentage of cycling cows in the first month of the mating period (P = 0.08) and early pregnancy rate (P = 0.09), but increased (P = 0.02) total pregnancy rate (Table 2). Alternatively, pre-mating supplementation did not affect any of the reproductive variables studied (P>0.10).

Discussion

The hypothesis that a strategic supplementation with a mix of whole rice bran and crude glycerin supplement before calving and before mating would improve the energy balance and productive and reproductive performance of beef cows grazing native swards was accepted. Prepartum and pre-mating supplementation improved energy balance compared with that observed in unsupplemented cows. This was reflected by an increase in plasma concentrations of cholesterol, glucose, and insulin and a decrease in BHB, NEFA, and urea concentrations. This improved hormonal and metabolite milieu resulted in a better BCS at calving (prepartum supplementation) and a small increase in milk production (pre-mating supplementation). However, only prepartum supplementation improved reproductive performance by increasing total pregnancy rate.

It is well established that cows must be fed adequately before and after calving to achieve optimal reproductive and productive performance (Perry et al., 1991Perry, R. C.; Corah, L. R.; Cochran, R. C.; Beal, W. E.; Stevenson, J. S.; Minton, J. E.; Simms, D. D. and Brethour, J. R. 1991. Influence of dietary energy on follicular development, serum gonadotropins and first postpartum ovulation in suckled beef cows. Journal of Animal Science 69:3762-3773. https://doi.org/10.2527/1991.6993762x
https://doi.org/10.2527/1991.6993762x...
). This is even more important with heifers because they must cover their pregnancy demands over their own growth requirements (Bellows et al., 1982Bellows, R. A.; Short, R. E. and Richardson, G. V. 1982. Effects of sire, age of dam and gestation feed level on dystocia and postpartum reproduction. Journal of Animal Science 55:18-27. https://doi.org/10.2527/jas1982.55118x
https://doi.org/10.2527/jas1982.55118x...
; Short et al., 1990Short, R. E.; Bellows, R. A.; Staigmiller, R. B.; Berardinelli, J. G. and Custer, E. E. 1990. Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle. Journal of Animal Science 68:799-816. https://doi.org/10.2527/1990.683799x
https://doi.org/10.2527/1990.683799x...
; Lalman et al., 2000Lalman, D. L.; Williams, J. E.; Hess, B. W.; Thomas, M. G. and Keisler, D. H. 2000. Effect of dietary energy on milk production and metabolic hormones in thin, primiparous beef heifers. Journal of Animal Science 78:530-538. https://doi.org/10.2527/2000.783530x
https://doi.org/10.2527/2000.783530x...
). In the present study, prepartum unsupplemented primiparous cows grazing native grassland could not meet their energy requeriments; therefore, they suffered a NEB. Cows had to mobilize body lipid and protein reserves to cover their energy demands, which was reflected in an increase of plasma concentration of NEFA, BHB, and urea (Guedon et al., 1999Guedon, L.; Saumande, J. and Desbals, B. 1999. Relationships between calf birth weight, prepartum concentrations of plasma energy metabolites and resumption of ovulation postpartum in Limousine suckled beef cows. Theriogenology 52:779-789. https://doi.org/10.1016/S0093-691X(99)00171-5
https://doi.org/10.1016/S0093-691X(99)00...
; Holcomb et al., 2001Holcomb, C. S.; Van Horn, H. H.; Head, H. H.; Hall, M. B. and Wilcox, C. J. 2001. Effects of prepartum dry matter intake and forage percentage on postpartum performance of lactating dairy cows. Journal of Dairy Science 84:2051-2058. https://doi.org/10.3168/jds.S0022-0302(01)74649-8
https://doi.org/10.3168/jds.S0022-0302(0...
; Reynolds et al., 2003Reynolds, C. K.; Aikman, P. C.; Lupoli, B.; Humphries, D. J. and Beever, D. E. 2003. Splanchnic metabolism of dairy cows during the transition from late gestation through early lactation. Journal of Dairy Science 86:1201-1217. https://doi.org/10.3168/jds.S0022-0302(03)73704-7
https://doi.org/10.3168/jds.S0022-0302(0...
; Dann et al., 2005Dann, H. M.; Morin, D. E.; Bollero, G. A.; Murphy, M. R. and Drackley, J. K. 2005. Prepartum intake, postpartum induction of ketosis, and periparturient disorders affect the metabolic status of dairy cows. Journal of Dairy Science 88:3249-3264. https://doi.org/10.3168/jds.S0022-0302(05)73008-3
https://doi.org/10.3168/jds.S0022-0302(0...
; Quintans et al., 2010Quintans, G.; Banchero, G.; Carriquiry, M.; López-Mazz, C. and Baldi, F. 2010. Effect of body condition and suckling restriction with and without presence of the calf on cow and calf performance. Animal Production Science 50:931-938. https://doi.org/10.1071/AN10021
https://doi.org/10.1071/AN10021...
; Soca et al., 2013Soca, P.; Carriquiry, M.; Keisler, D. H.; Claramunt, M.; Do Carmo, M.; Olivera-Muzante, J.; Rodríguez, M. and Meikle, A. 2013. Reproductive and productive response to suckling restriction and dietary flushing in primiparous grazing beef cows. Animal Production Science 53:283-291. https://doi.org/10.1071/AN12168
https://doi.org/10.1071/AN12168...
).

For this motive, we reasoned that supplementation in late gestation would be a logical alternative to cover the cows’ pregnancy energy requeriments making the use of less necessary reserves, and then if any spare, it would be used to improve reproduction. In fact, the increase of energy and nutrient intake by the prepartum supplemented cows contributed to reduce the NEB. Supplementation avoided energy coming from catabolism, as was reflected by the better plasma concentration of glucose. Therefore, catabolic activity decreased, reflected by a reduction in NEFA, BHB, and urea plasma concentration, and the anabolic activity increased, indicated by an improved plasma concentration of albumin and cholesterol. The cows were less dependent from energy coming from body reserves, which reflected on a lighter decrease in BCS at calving and higher total pregnancy rate compared with unsupplemented cows.

Body condition score at calving, which is a consequence of prepartum nutrition (Wettemann et al., 2003Wettemann, R. P.; Lents, C. A.; Ciccioli, N. H.; White, F. J. and Rubio, I. 2003. Nutritional and suckling mediated anovulation in beef cows. Journal of Animal Science 81:E48-E59.), is the primary factor determining the length of postpartum anestrus and the probability of pregnancy (Hess et al., 2005Hess, B. W.; Lake, S. L.; Scholljegerdes, E. J.; Weston, T. R.; Nayigihugu, V.; Molle, J. D. C. and Moss, G. E. 2005. Nutritional controls of beef cow reproduction. Journal of Animal Science 83:E90-E106; Montiel and Ahuja, 2005Montiel, F. and Ahuja, C. 2005. Body condition and suckling as factor influencing the duration of postpartum anestrus in cattle: a review. Animal Reproduction Science 85:1-26. https://doi.org/10.1016/j.anireprosci.2003.11.001
https://doi.org/10.1016/j.anireprosci.20...
; Soca et al., 2013Soca, P.; Carriquiry, M.; Keisler, D. H.; Claramunt, M.; Do Carmo, M.; Olivera-Muzante, J.; Rodríguez, M. and Meikle, A. 2013. Reproductive and productive response to suckling restriction and dietary flushing in primiparous grazing beef cows. Animal Production Science 53:283-291. https://doi.org/10.1071/AN12168
https://doi.org/10.1071/AN12168...
). Indeed, more prepartum supplemented cows were pregnant at the end of the breeding period. Hunter (1991)Hunter, R. A. 1991. Strategic supplementation for survival, reproduction and growth of cattle. p.32-47. In: Proceedings 2nd Grazing Livestock Nutrition Conference. McCollum, F. T. and Judkins, M. B., eds. Oklahoma, USA suggested that the prepartum nutrition plan affects the development of follicles that mature in the subsequent breeding season, and this could be because folliculogenesis takes 80 to 100 days (Britt, 1991Britt, J. H. 1991. Impacts of early postpartum metabolism on follicular development and fertility. The Bovine Practitioner Proceeding 24:39-43.). It is also possible that the prepartum nutrition plan affects oocyte quality (Krisher, 2004Krisher, R. L. 2004. The effect of oocyte quality on development. Journal of Animal Science 82:E14-E23), size, and steriodogenic capacity of the corpus luteum, and uterine function through mechanisms that cause extended anestrus (Lucy, 2003Lucy, M. C. 2003. Mechanisms linking nutrition and reproduction in postpartum cows. Reproduction Supplement 61:415-427. https://doi.org/10.1530/biosciprocs.5.031
https://doi.org/10.1530/biosciprocs.5.03...
), all of these mechanisms resulting in an improved reproductive outcome.

Our results are in agreement with those of other authors who reported benefits on reproduction when primiparous (Wiley et al., 1991Wiley, J. S.; Petersen, M. K.; Ansotegui, R. P. and Bellows, R. A. 1991. Production from first-claf beef heifers fed a maintenance or low level of prepartum nutrition and ruminally undegradable or degradable protein postpartum. Journal of Animal Science 69:4279-4293. https://doi.org/10.2527/1991.69114279x
https://doi.org/10.2527/1991.69114279x...
; Soto et al., 2001Soto, R.; Rubio, I.; Galina, C. S.; Castillo, E. and Rojas, S. 2001. Effect of pre- and post-partum feed supplementation on the productive and reproductive performance of grazing primiparous Brahman cows. Tropical Animal Health and Production 33:253-264. https://doi.org/10.1023/A:1010370906515
https://doi.org/10.1023/A:1010370906515...
) or multiparous (Quintans et al., 2016Quintans, G.; Scarsi, A.; Roig, G.; Carriquiry, M. and Banchero, G. 2016. Influence of a short-term prepartum supplementation on beef cows and calves’ performance in pastoral conditions. Animal Production Science 56:1913-1919. https://doi.org/10.1071/AN15082
https://doi.org/10.1071/AN15082...
) cows were well fed or supplemented before calving. However, Stalker et al. (2006)Stalker, L. A.; Adams, D. C.; Klopfenstein, T. J.; Feuz, D. M. and Funston, R. N. 2006. Effects of pre- and postpartum nutrition on reproduction in spring calving cows and calf feedlot performance. Journal of Animal Science 84:2582-2589. https://doi.org/10.2527/jas.2005-640
https://doi.org/10.2527/jas.2005-640...
did not find a positive impact of prepartum supplementation on pregnancy rates. These authors explained the lack of response of supplementary nutrition prepartum on reproductive outcome due to BCS at calving. They used mature cows in very good condition score (∼5.0 units of BCS), whereas in our experiment, we used primiparous cows with at least 10% less BCS (∼0.5 units less). In the same line, Scarsi (2012)Scarsi, A. 2012. Efecto de una suplementación corta preparto en variables metabólicas, productivas y reproductivas en vacas multíparas y primíparas para carne. Thesis (M.Sc.). Universidad de la República, Uruguay worked with primiparous cows and also reported no differences in reproductive performance when cows were supplemented before calving. However, in that case, the BCS at calving was not responsible for the lack of response, since their cows had about 10% less BCS than ours, 4.5 vs. 4.1 in the present study and in Scarsi (2012)Scarsi, A. 2012. Efecto de una suplementación corta preparto en variables metabólicas, productivas y reproductivas en vacas multíparas y primíparas para carne. Thesis (M.Sc.). Universidad de la República, Uruguay, respectively. These results suggest that the window of BCS where prepartum supplementation exerts an effect on reproduction is narrow and should be considered when doing prepartum supplementation.

Our results are also in agreement with those of Clariget et al. (2016b)Clariget, J. M.; Román, L.; Karlen, M.; Álvarez-Oxiley, A.; López-Mazz, C. and Pérez-Clariget, R. 2016b. Supplementation with a mixture of whole rice bran and crude glycerin on metabolic responses and performance of primiparous beef cows. Revista Brasileira de Zootecnia 45:16-25. https://doi.org/10.1590/S1806-92902016000100003
https://doi.org/10.1590/S1806-9290201600...
and Astessiano et al. (2013)Astessiano, A. L.; Pérez-Clariget, R.; Espasandín, A. C.; López-Mazz, C.; Soca, P. and Carriquiry, M. 2013. Metabolic, productive and reproductive responses to postpartum short-term supplementation in primiparous beef cows. Revista Brasileira de Zootecnia 42:246-253. https://doi.org/10.1590/S1516-35982013000400003
https://doi.org/10.1590/S1516-3598201300...
, who reported no benefits on reproduction when cows were supplemented before or during mating. Unlike our study, those authors worked with cows with less than 50 DPP when cows would be allocating the consumed energy to milk production and not to reproductive functions (Short et al., 1990Short, R. E.; Bellows, R. A.; Staigmiller, R. B.; Berardinelli, J. G. and Custer, E. E. 1990. Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle. Journal of Animal Science 68:799-816. https://doi.org/10.2527/1990.683799x
https://doi.org/10.2527/1990.683799x...
). However, our results do not agree with those obtained by Carrere et al. (2005)Carrere, J. M.; Casella, C. G. and Mitrano, F. J. 2005. Efecto del flushing y del destete temporario sobre el comportamiento reproductivo de vacas de carne de segundo entore en anestro y en condiciones corporales subóptimas. Agronomy thesis. Universidad de la República, Montevideo, Uruguay, Soca et al. (2005Soca, P.; Olivera, J.; Rodríguez-Irazoqui, M.; Martínez-Cal, H. and Rubianes, R. 2005. Porcentaje de preñez y cambio de estado corporal de vacas de cría suplementadas con afrechillo de arroz y sometidas a destete temporario. p.456. In: 6° Simposio Internacional de Reproducción Animal. Córdoba, Argentina, 2013Astessiano, A. L.; Pérez-Clariget, R.; Espasandín, A. C.; López-Mazz, C.; Soca, P. and Carriquiry, M. 2013. Metabolic, productive and reproductive responses to postpartum short-term supplementation in primiparous beef cows. Revista Brasileira de Zootecnia 42:246-253. https://doi.org/10.1590/S1516-35982013000400003
https://doi.org/10.1590/S1516-3598201300...
), Do Carmo (2006)Do Carmo, M. 2006. Efecto del destete temporario y suplementación energética de corta duración sobre el comportamiento reproductivo y productivo de vacas de cría primíparas. Agronomy thesis. Universidad de la República, Montevideo, Uruguay, and Claramunt (2007)Claramunt, M. 2007. Efecto de la suplementación energética de corta duración y el destete temporario sobre el crecimiento folicular y desempeño reproductivo de vacas primíparas Hereford. Agronomy thesis. Universidad de la República, Montevideo, Uruguay, who observed higher percentages of early and total pregnancy rate on supplemented cows compared with controls cows. In the previous studies, the cows had similar DPP to those in our work (61 vs. 59 days, respectively), but they had lower BCS at the onset of the treatment (3.5 vs. 4.2 units, respectively). Since their control cows had lower early and total pregnancy rates than ours (33 vs 52 and 63 vs 80%, respectively), it could be considered that our cows were already in good herbage condition (availability herbage more than 2000 kg DM/ha; HA: 10 kg/100 kg of BW per day; CP: 110 g/kg) to have an increment in pregnancy rate by adding any extra feed. Indeed, pre-mating supplementation only increased milk production by 8.5%, but there was no effect on calf weight gain or cow BCS or BW.

We expected that an additional supplementation during the pre-mating period will boost the energy supply to the cow and increase the reproductive outcome attained by the prepartum supplementation alone; however, the interaction between supplementation periods did not affect the variables studied. Although pre-mating supplementation improved energy balance, indicated by a decrease on plasma concentration of NEFA, BHB, and urea and by a rise in cholesterol (Ndlovu et al., 2007Ndlovu, T.; Chimonyo, M.; Okoh, A. I.; Muchenje, V.; Dzama, K. and Raats, J. G. 2007. Assessing the nutritional status of beef cattle: current practices and future prospects. African Journal of Biotechnology 6:2727-2734. https://doi.org/10.5897/AJB2007.000-2436
https://doi.org/10.5897/AJB2007.000-2436...
), the impact was smaller than prepartum supplementation. It is possible that in our experiment, differently from that of Soto et al. (2001)Soto, R.; Rubio, I.; Galina, C. S.; Castillo, E. and Rojas, S. 2001. Effect of pre- and post-partum feed supplementation on the productive and reproductive performance of grazing primiparous Brahman cows. Tropical Animal Health and Production 33:253-264. https://doi.org/10.1023/A:1010370906515
https://doi.org/10.1023/A:1010370906515...
, who reported an increased pregnancy rate only when cows were supplemented pre- and postpartum, our second supplementation was not accurate enough to do so. Within the possible interfering factors, a higher allowance of herbage than the prepartum (7.5 or 10 kg/100 kg of BW per day), physiological status of the cow (late pregnancy or lactating cow), and duration of supplementation periods (52 or 21 days) could explain, at least partially, the different effects between both supplementation regimens.

An additional advantage of short supplementation period of less than 75 days before calving is that it seems not to influence calf birth weight (Wiley et al., 1991Wiley, J. S.; Petersen, M. K.; Ansotegui, R. P. and Bellows, R. A. 1991. Production from first-claf beef heifers fed a maintenance or low level of prepartum nutrition and ruminally undegradable or degradable protein postpartum. Journal of Animal Science 69:4279-4293. https://doi.org/10.2527/1991.69114279x
https://doi.org/10.2527/1991.69114279x...
; Bellows et al., 2001Bellows, R. A.; Grings, E. E.; Simms, D. D.; Geary, T. W. and Bergman, J. W. 2001. Effects of feeding supplemental fat during gestation to first-calf beef heifers. The Professional Animal Scientist 17:81-89.; Soto et al., 2001Soto, R.; Rubio, I.; Galina, C. S.; Castillo, E. and Rojas, S. 2001. Effect of pre- and post-partum feed supplementation on the productive and reproductive performance of grazing primiparous Brahman cows. Tropical Animal Health and Production 33:253-264. https://doi.org/10.1023/A:1010370906515
https://doi.org/10.1023/A:1010370906515...
; Alexander et al., 2002Alexander, B. M.; Hess, B. W.; Hixon, D. L.; Garrett, B. L.; Rule, D. C.; McFarland, M.; Bottger, J. D.; Moss, G. E. and Simms, D. D. 2002. Influence of prepartum fat supplementation on subsequent beef cow reproduction and calf performance. The Professional Animal Scientist 18:351-357.; Scarsi, 2012Scarsi, A. 2012. Efecto de una suplementación corta preparto en variables metabólicas, productivas y reproductivas en vacas multíparas y primíparas para carne. Thesis (M.Sc.). Universidad de la República, Uruguay; Quintans et al., 2016Quintans, G.; Scarsi, A.; Roig, G.; Carriquiry, M. and Banchero, G. 2016. Influence of a short-term prepartum supplementation on beef cows and calves’ performance in pastoral conditions. Animal Production Science 56:1913-1919. https://doi.org/10.1071/AN15082
https://doi.org/10.1071/AN15082...
). Indeed, in the present experiment, calves’ weight at calving was not influenced by supplementation, and no difficulties at calving were observed. On the other hand, long prepartum supplementation of 100 days or more before calving increases calf birth weight (Corah et al., 1975Corah, L. R.; Dunn, T. G. and Kaltenbach, C. C. 1975. Influence of prepartum nutrition on the reproductive performance of beef females and the performance of their progeny. Journal of Animal Science 41:819-824. https://doi.org/10.2527/jas1975.413819x
https://doi.org/10.2527/jas1975.413819x...
; Perry et al., 1991Perry, R. C.; Corah, L. R.; Cochran, R. C.; Beal, W. E.; Stevenson, J. S.; Minton, J. E.; Simms, D. D. and Brethour, J. R. 1991. Influence of dietary energy on follicular development, serum gonadotropins and first postpartum ovulation in suckled beef cows. Journal of Animal Science 69:3762-3773. https://doi.org/10.2527/1991.6993762x
https://doi.org/10.2527/1991.6993762x...
; Radunz et al., 2010Radunz, A. E.; Fluharty, F. L.; Day, M. L.; Zerby, H. N. and Loerch, S. C. 2010. Prepartum dietary energy source fed to beef cows: I. Effects on pre- and postpartum cow performance. Journal of Animal Science 88:2717-2728. https://doi.org/10.2527/jas.2009-2744
https://doi.org/10.2527/jas.2009-2744...
) and could induce calving difficulties (Gunn et al., 2014Gunn, P. J.; Schoonmaker, J. P.; Lemenager, R. P. and Bridges, G. A. 2014. Feeding excess crude protein to gestating and lactating beef heifers: impact on parturition, milk composition, ovarian function, reproductive efficiency and pre-weaning progeny growth. Livestock Science 167:435-448. https://doi.org/10.1016/j.livsci.2014.05.010
https://doi.org/10.1016/j.livsci.2014.05...
). Long supplementation periods have more chance to result in calf dystocia than shorter ones, since good nutrition can increase the size and fuction of the placenta (Rasby et al., 1990Rasby, R. J.; Wettemann, R. P.; Geisert, R. D.; Rice, L. E. and Wallace, C. R. 1990. Nutrition, body condition and reproduction in beef cows: fetal and placental development, and estrogens and progesterone in plasma. Journal of Animal Science 68:4267-4276. https://doi.org/10.2527/1990.68124267x
https://doi.org/10.2527/1990.68124267x...
), which has a high correlation with the size of the calves (Echternkamp, 1993Echternkamp, S. E. 1993. Relationship between placental development and calf birth weight in beef cattle. Animal Reproduction Science 32:1-13. https://doi.org/10.1016/0378-4320(93)90053-T
https://doi.org/10.1016/0378-4320(93)900...
).

Postpartum supplementation had greater impact on milk production than the prepartum supplementation as has been reported before by Wiley et al. (1991)Wiley, J. S.; Petersen, M. K.; Ansotegui, R. P. and Bellows, R. A. 1991. Production from first-claf beef heifers fed a maintenance or low level of prepartum nutrition and ruminally undegradable or degradable protein postpartum. Journal of Animal Science 69:4279-4293. https://doi.org/10.2527/1991.69114279x
https://doi.org/10.2527/1991.69114279x...
and Lalman et al. (2000)Lalman, D. L.; Williams, J. E.; Hess, B. W.; Thomas, M. G. and Keisler, D. H. 2000. Effect of dietary energy on milk production and metabolic hormones in thin, primiparous beef heifers. Journal of Animal Science 78:530-538. https://doi.org/10.2527/2000.783530x
https://doi.org/10.2527/2000.783530x...
. However, the increase in milk production in our experiment was less than 10% and was not reflected in an increased weaning weight of the calves. The reason might be that in our experiment, supplementation was not started until 59 days postpartum, and it has been reported that after the first 60 days of age, daily weight gain of calves does not depend only on milk production (Neville Jr. et al., 1962Neville Jr., W. E. 1962. Influence of dam's milk production and other factors on 120- and 240-day weight of Hereford calves. Journal of Animal Science 21:315-320. https://doi.org/10.2527/jas1962.212315x
https://doi.org/10.2527/jas1962.212315x...
). Indeed, the correlation between calf weight gain and dam milk production decreased from 0.74 in the first 60 days of life to 0.63 in the next 60 days.

Conclusions

In extensive pastoral system production, pregnancy rate and weaning weights are the primary limitations of the cow-calf operation that might be mitigated with a strategic supplementation. However, the evaluation of cheap feeds such as crude glycerin and rice bran, which are not used for human nutrition, is desirable. Mixing them as a supplement and offering them to cows in small quantities (0.4 kg/100 kg of BW) and in a strategic moment (last two months of gestation) increases total pregnancy rate with no additional effect to supplement those cows during the pre-mating period.

Acknowledgments

We thank ANII for providing a scholarship POS_2011_1_3522 and FMV_3_2011_1_6713 projects, which financed part of this work; ALUR, for providing glycerin with which this work was conducted; and the staff of EEBR, in particular, Oscar Cáceres, Dorrel Bentancour, and agronomist Carlos Mantero.

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Publication Dates

  • Publication in this collection
    15 May 2020
  • Date of issue
    2020

History

  • Received
    21 June 2019
  • Accepted
    19 Jan 2020
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