Zootechnical performance of lambs fed different levels of black wattle tanin extractAbstract
The objective of this work was to evaluate the effect of different levels of black wattle tannin extract on the intake, performance, and carcass characteristics of lambs in confinement. Forty uncastrated, 50-day-old, Texel x Ile de France male lambs were used. The treatments consisted of the following five levels of added tannin extract (percentage of total dry matter in the diet): 0 (control), 1.0, 2.0, 3.0, and 4.0%. A quadratic effect was observed for the intake of dry matter, organic matter, crude protein, ether extract, neutral detergent fiber, total carbohydrates, non-structural carbohydrates, and total digestible nutrients, as well as for average daily weight gain, whose maximum value was 0.303 kg at the level of 1.6% tannin extract. There was also a quadratic effect for hot and cold carcass yields, subcutaneous fat thickness, fat content, and carcass conformation. The level of 1.6% black wattle tannin extract is recommended to be added to the total dry matter of the diet of lambs in confinement due to the obtained highest weight gains, higher dry matter and nutrient intake, and greater average daily gain, which improve the body condition score and conformation at slaughter of the animals.
Index terms:
Ovis aries; confinement; polyphenols; weight gain.
Resumo
O objetivo deste trabalho foi avaliar o efeito de diferentes níveis de extrato de tanino de acácia-negra sobre o consumo, o desempenho e as características de carcaça de cordeiros confinados. Foram utilizados 40 cordeiros machos Texel x Ile de France, não castrados, com 50 dias de idade. Os tratamentos consistiram nos seguintes cinco níveis de inclusão de extrato de tanino (percentagem da matéria seca total da dieta): 0 (controle), 1,0, 2,0, 3,0 e 4,0%. Observou-se efeito quadrático sobre os consumos de matéria seca, matéria orgânica, proteína bruta, extrato etéreo, fibra em detergente neutro, carboidratos totais, carboidratos não estruturais e nutrientes digestíveis totais, bem como sobre ganho de peso médio diário, cujo ponto máximo foi de 0,303 kg no nível de 1,6% de extrato de tanino. Também houve efeito quadrático sobre os rendimentos de carcaça quente e fria, a espessura de gordura subcutânea, o estado de engorduramento e a conformação das carcaças. Recomenda-se a adição de 1,6% de extrato de tanino de acácia-negra na matéria seca total da dieta de cordeiros confinados devido aos melhores ganhos de peso, ingestão de matéria seca e de nutrientes, e ganho médio de peso obtidos, o que melhora o escore de condição corporal e a conformação no abate dos animais.
Termos para indexação:
Ovis aries; confinamento; polifenóis; ganho de peso.
Introduction
Sheep farming for meat production has been expanding in Brazil in recent years, influenced by the steadily growing market for lamb and mutton (Costa et al., 2024). To meet market demands, sheep producers have sought to improve production techniques, focusing on meat quality and on increasing productivity. Sheep confinement is considered an alternative for intensifying production and making the production system more efficient during the finishing phase of the animals (Souza et al., 2014).
In sheep confinement, feed intake is a crucial factor since an adequate nutrition is essential for a good animal performance and development. In this context, the use of tannins in sheep diets is an interesting alternative due to the potential improvements in animal performance (Orlandi et al., 2020a). According to Vieira et al. (2020), tannins are phenolic compounds found in plants that show the ability to form complexes with proteins and carbohydrates and reduce rumen degradation. Based on this, earlier studies have shown that tannins can improve nitrogen use by ruminants, as well as feed conversion and animal performance (Orlandi et al., 2020b). However, when used at high doses, tannins cause a repulsive odor and astringency, considered anti-nutritional factors that lead to a reduced palatability (Costa et al., 2021a), which alters the animal’s ingestive behavior and, consequently, reduces feed consumption.
Besharati et al. (2022), in a review on the use of tannins in ruminant feed, concluded that the addition of high levels in the dry matter of the animal diet can lead to adverse effects related to a reduced feed intake and consequent lower weight gain. In this line, Costa et al. (2021a) stated that, as the levels of tannins (0, 20, 40, 60, and 80 g total carbohydrates per kilogram of dry matter) in the diet increased, there was a reduction in the carcass characteristics of sheep in confinement. Therefore, at high percentages in the diet, tannins may become toxic and affect animal performance.
In the literature, there have also been reports of positive effects of the addition of tannin extract in animal diets depending on the used doses. Chiaia et al. (2016), for example, tested the use of different levels of tannins and reported a better feed conversion for animals fed a diet containing 1.5% tannins (percentage of dry matter) than only 0.2%, a result attributed to the increased availability of dietary protein to be absorbed at the intestinal level. Lima et al. (2019) observed that black wattle (Acacia mearnsii De Wild.) tannin extract at a dose of 30 g kg-1 affected the ingestive behavior of sheep, increasing total feeding time.
The objective of this work was to evaluate the effect of different levels of black wattle tannin extract on the intake, performance, and carcass characteristics of lambs in confinement.
Materials and Methods
The experiment was carried out at Universidade Federal de Santa Maria, located in the municipality of Santa Maria, in the state of Rio Grande do Sul, Brazil (29º43'S, 53º42'W, at an altitude of 95m). The climate is of the Cfa type, humid subtropical, according to Köppen’s classification. Forty uncastrated Texel x Ile de France crossbred male lambs were used, weaned at 50 days of age and properly dewormed and vaccinated against clostridiosis. The animals were confined in individual and fully-covered pens (2.0 m2 per animal) with slatted floors approximately 1.0 m above the ground. Each pen was equipped with an individual feeder and water trough.
The animals were distributed in a completely randomized experimental design of five treatments, each with eight replicates. The treatments consisted of different levels of black wattle tannin extract added to the diet, as follows: 0 (control), 1.0, 2.0, 3.0, and 4.0% of total dry matter.
The experimental period included 10 days for adaption to the facilities, feed, and handling. The lambs were weighed at the start of the experimental phase and then every 14 days to monitor their performance, always after fasting for 14 hours. The animals were slaughtered after a fixed period of 60 days.
The total diet was offered ad libitum and consisted of maize silage as bulk and a concentrate comprising crushed maize, soybean meal, calcitic limestone, and common salt, with different doses of black wattle tannin extract added according to each treatment. A bulk-to-concentrate ratio of 45:55, on a dry matter basis, was used. The diets were formulated to be isoproteic as described by National Research Council (NRC, 2007) and calculated to meet the requirements of the category (Table 1).
Percentage of ingredients and chemical composition of the experimental diets fed to lambs in confinement.
During the experiment, the animals were fed daily in the morning (8:30 a.m.) and in the afternoon (5:30 p.m.), allowing for approximately 15% of the feed to be left over per day to ensure maximum voluntary consumption. Samples of the leftovers and feed were collected every 7 days and formed into composite samples, which were packed in plastic bags, identified, and stored in a freezer, at -20°C, for later laboratory analysis.
For the bromatological analysis, the food samples and leftovers were pre-dried in a forced-air oven, at 55°C, for approximately 72 hours, then ground in a Willey mill with a 1.0 mm sieve, packed in bottles, and labelled.
The dry matter content of the feed and leftovers was determined by oven drying, at 105°C, for at least 16 hours, being expressed in kilograms per day, percentage of live weight (LW), and g kg-1 LW0.75 (Tables 2, 3, and 4, respectively). Ash content was obtained by combustion, at 600°C, for 4 hours (Silva & Queiroz, 2002). The levels of total nitrogen were determined by the Kjeldahl method, following method 984.13 of Association of Official Analytical Chemists (AOAC) (Cunniff, 1997). The levels of ether extract were obtained according to Silva & Queiroz (2002). To determine the concentration of neutral detergent fiber, the samples were placed in polyester bags and treated with a neutral detergent solution in an autoclave, at 110°C, for 40 min; a-amylase was used for the samples of concentrate. Acid detergent fiber was obtained using method 973.18 of AOAC (Cunniff, 1997). Total carbohydrates were determined as described in Sniffen et al. (1992), using the equation: total carbohydrates (%) = 100 - (% crude protein + % ether extract + % ash content).
Average intake of dry matter (DMI), organic matter (OMI), crude protein (CPI), ether extract (EEI), neutral detergent fiber (NDFI), acid detergent fiber (ADFI), total carbohydrates (TCHI), non-structural carbohydrates (NSCI), and total digestible nutrients (TDNI), expressed in kilograms per day, by lambs fed different levels of black wattle (Acacia mearnsii) tannin extract in their diet.
Average intake of dry matter (DMI), organic matter (OMI), crude protein (CPI), ether extract (EEI), neutral detergent fibre (NDFI), acid detergent fibre (ADFI), total carbohydrates (TCHI), non-structural carbohydrates (NSCI), and total digestible nutrients (TDNI), expressed as percentage of live weight, by lambs fed different levels of black wattle (Acacia mearnsii) tannin extract in their diet.
Average intake of dry matter (DMI), organic matter (OMI), crude protein (CPI), ether extract (EEI), neutral detergent fiber (NDFI), acid detergent fiber (ADFI), total carbohydrates (TCHI), non-structural carbohydrates (NSCI), and total digestible nutrients (TDNI), expressed in g kg-1 live weight0.75, by lambs fed different levels of black wattle (Acacia mearnsii) tannin extract in their diet.
The difference between the amount of feed offered and the leftovers (on a dry matter basis) was used to calculate the daily intake of dry matter, organic matter, crude protein, ether extract, neutral detergent fiber, acid detergent fiber, total carbohydrates, non-structural carbohydrates, and total digestible nutrients.
Once the lambs had completed the 60 day experimental period, they were handcuffed to obtain their farm live weight. Then, they were fasted for 14 hours and weighed again to determine their slaughter live weight. Fasting losses were obtained from the difference between farm live weight and slaughter live weight. The body condition score was then evaluated together with in vivo conformation using a method adapted from Osório et al. (1998), consisting of assigning a value from 1 to 5, in increments of 0.25, where 1 is very poor and 5 is excellent. The animals were then stunned and slaughtered by bleeding.
After each slaughter, carcass was weighed to determine hot carcass weight. Hot carcass yield was obtained through the equation: HCY = (HCW/LWS) x 100, where HCY is hot carcass yield, HCW is hot carcass weight, and LWS is slaughter live weight. Each carcass was then chilled for 24 hours in a cold chamber, at 1°C, and weighed again to calculate cold carcass weight, cold carcass yield, and the chilling loss index. Cold carcass yield and the chilling loss index were obtained using the following equations: CCY = (CCW/LWS) x 100 and CLI = 100-((CCW/HCW) x 100), respectively, where CCY is cold carcass yield, CCW is cold carcass weight, LWS is slaughter live weight, CLI is the chilling loss index, and HCW is hot carcass weight. To show the development of the carcass, its fat content was evaluated subjectively by estimating the amount of fat distribution, using a range similar to that for carcass conformation, from 1 to 5, where 1 is excessively lean and 5 is excessively fat.
Each carcass was then immediately split longitudinally into two halves using an electric saw. To assess the left half of the carcass, measurements were taken of the length of the carcass, length of the leg, width of the leg, and depth of the chest according to Osório et al. (1998).
The longissimus dorsi muscle of the left half of the carcass was exposed through a transverse cut between the twelfth and thirteenth ribs in order to determine color, texture, and marbling. Color was assessed visually, by assigning scores on a scale from 1 to 5, in increments of 0.5, where 1 represents light pink and 5, dark red. Texture was evaluated by a subjective visual assessment of the size of the fiber bundles, assigned scores from 1 to 5, in increments of 0.5, where 1 is very coarse and 5 is very fine. Marbling was also determined by visual observation by classifying intramuscular fat on a scale from 1 to 5, where 1 is nonexistent and 5 is excessive (Osório et al., 1998). To obtain loin eye area, an outline of the muscle was drawn on tracing paper using the AutoCAD software (Autodesk, San Francisco, CA, USA) with a graphics tablet for the readings. Subcutaneous fat thickness was assessed in the same region and measured in millimeters, using a digital caliper.
After processing, the right half of the carcass was split into four commercial cuts: leg, shoulder, ribs, and neck according to Osório et al. (1998). The cuts were weighed separately to calculate their proportion of cold carcass weight.
The experimental design was completely randomized, with eight replicates used to evaluate the five treatments. After data collection, the results were subjected to the analysis of variance and regression analysis. The adopted equations were selected based on the coefficients of determination and the significance of the regression coefficients, using the t-test at a 5% significance level.
Results and Discussion
There was a quadratic effect of level of tannin in the diet on the intakes of dry matter, organic matter, crude protein, ether extract, neutral detergent fiber, total carbohydrates, non-structural carbohydrates, and total digestible nutrients. This means that nutrient intake tends to increase up to a maximum level and then to decrease. The maximum dry matter intake was 1.63 kg per day at 1.7% tannin addition to the total dry matter of the diet. However, the coefficient of determination of the equation was low due to the high coefficient of variation observed for the data.
An adequate dry matter intake is important for sheep performance, which is directly linked to the intake of nutrients from the diet. According to Costa et al. (2021b), feed intake is influenced by several factors, among which the fiber content of a diet stands out. In the present study, neutral detergent fiber reached values close to the 30% recommended in the literature (Kosloski et al., 2006) regardless of the used level of tannins (Table 1). Taking into account energy content, there was a small variation in the proportion of neutral detergent fiber in the bromatological composition of the diets, meaning that there was a small probability of differences in intake being caused by any physiological control of feeding. The levels of moisture and ether extract also varied little between diets and were at levels below those reported in the literature as having a negative effect on intake, i.e., 50% moisture and 5.0% ether extract (Grandis et al., 2015).
There was a reduction in intake at 1.7% tannins in the total dry matter of the diet, which can be attributed to a reduction in palatability due to the high levels of concentrated tannin that can reduce nutrient intake and digestibility, resulting in a reduced animal performance (Silva et al., 2016; Min & Solaiman, 2018). However, at moderate levels of tannin in the diet, i.e., below 1.7% of dry matter, there was an increase in the consumption and weight gain of the animals, representing the benefits of using adequate tannin levels.
In relation to crude protein intake, regardless of the level of tannin in the diet, all values were higher than that of 116 g crude protein per day recommended by NRC (2007) for late-maturing lambs with a live weight of 20 kg and daily gain of 200 g. The maximum crude protein intake estimated from the regression equation was 0.317 kg per day at a level of 1.7% tannin extract in the diet, in line with the result obtained for dry matter intake. Similarly, when evaluating the intake of total digestible nutrients, values higher than that of 0.39 kg per day recommended by the NRC were observed for all treatments. The maximum intake of total digestible nutrients was 1.117 kg per day at a tannin extract level of 1.6% of the total dry matter of the diet. These intake levels are important since they relate to nutrients that have a direct influence on animal performance, specifically on weight gain, degree of finishing, and carcass characteristics.
In the evaluation of the variables related to animal performance, the increase in tannin extract in the diet showed a quadratic effect on the average daily weight gain, in vivo conformation, and body condition score of the lambs at slaughter (Table 5). The maximum value for average daily weight gain was 0.306 kg per day, obtained at a level of 1.6% tannin extract in the diet. This result can be attributed to dry matter intake, which reached a maximum at 1.7% added tannins and determined the maximum intake of crude protein and total digestible nutrients at a level of 1.6 and 1.7% tannin extract in the diet, respectively.
Mean values for initial live weight (ILW), farm live weight (FLW), weight at slaughter after fasting (LWS), fasting loss (FL), average daily weight gain (ADG), feed conversion (FC), conformation, and body condition score (BCS) of lambs fed different levels of black wattle (Acacia mearnsii) tannin extract in their diet.
According to Gemeda & Hassen (2015), tannins act as a nutrient modulator, leading to a reduction in the action of methanogenic bacteria in the rumen and, consequently, in methane production. This has two important implications for the use of tannins: an improvement in energy use due to a reduction in the energy lost in the form of methane, helping to improve animal productive performance; and a reduction in the production and emission of methane, an effective way of achieving a more sustainable animal production, a major environmental issue today. With a higher dry matter intake and a consequent higher nutrient intake, there was a greater average daily gain, resulting in animals with a better body condition score and better conformation at slaughter. The variables for initial live weigh, farm live weight, live weight at slaughter, fasting loss, and feed conversion were not significantly affected by the addition of tannin extract.
From the derived regression equation, a maximum conformation of 3.38 was obtained at the level of 1.6% tannin extract in the dry matter of the diet, which was in line with the results for the average daily gain and intake of the animals. The maximum body condition score, which is directly related to the degree of pre-slaughter finishing of the animal, was 3.52 at 1.3% tannin extract, being 3.51 at 1.6%. Therefore, it can be inferred that the degree of finishing was adequate since the value of 3.5 is considered acceptable for slaughter sheep by meat-packing plants and is classified as very good in the literature (Osório et al., 1998).
The different levels of tannin extract had a quadratic effect on hot carcass yield and cold carcass yield (Table 6), which showed maximum values of 49.29 and 47.76%, respectively, at 1.2 and 1.1% tannin extract in the total dry matter of the diet. This result can be explained by the quadratic variation observed in total gastrointestinal content.
Mean values for lamb carcass characteristics and gastrointestinal content when fed different levels of black wattle (Acacia mearnsii) tannin extract in their diet(1).
According to the regression equation, the value for total gastrointestinal content decreased to 15.32% up to a tannin extract level of 1.1%, then started to increase. This finding is in line with the best results for carcass yield, considering the aforementioned values. Tannins, at moderate levels in the diet, can have a positive effect on the rumen degradation of dietary fiber, but, at high levels, can have a negative effect on fibrolytic bacteria and, consequently, on the degradation of the fibrous fraction of the feed (Besharati et al., 2022), increasing the gastrointestinal content of animals at slaughter.
The levels of tannin extract added to the diet also showed a quadratic effect on subcutaneous fat thickness, fat content, and conformation of the carcass. Subcutaneous fat thickness and fat content are important carcass characteristics that are directly related to the degree of finishing (represented by the body condition score) of the animals at slaughter. For these variables, the maximum values found were 2.76 and 3.55 mm, respectively, at 1.2 and 1.3% of tannin extract in the diet. These results can be explained by and are consistent with the body condition score of the animals at slaughter, for which the best value was obtained with 1.3% tannin extract. Although the maximum subcutaneous fat thickness value found in the present study is considered average and within the expected range for lambs (Mora et al., 2015), the animals fed 4.0% tannin extract in their diet had very little fat, representing a lack of finishing in their carcasses.
The maximum value obtained for carcass conformation was 3.5 at 1.6% tannin extract in the diet and is directly related to in vivo conformation, which also presented a value of 3.5 at this level. Therefore, evaluating the conformation of the animals before slaughter can be used for the assessment of the carcass of the lambs after slaughter. According to the scale of carcass conformation presented by Osório et al. (1998), the maximum value in the present study is considered very good, meaning that lambs fed 1.6% tannin extract in the total dry matter of the diet showed, not only a greater weight gain, but also carcasses with acceptable characteristics and a reasonable quality standard.
Conclusion
The addition of 1.6% black wattle (Acacia mearnsii) tannin extract to the total dry matter of the diet of lambs in confinement promotes the best gains in weight, body condition score, and conformation at slaughter.
Declaration of use of AI technologies
No generative artificial intelligence (AI) was used in this study.
Acknowledgments
To Seta S.A., for providing the black wattle tannin extract used in the study.
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The mention of specific chemical products, machines, and commercial equipment in the texts published in this journal does not imply their recommendation by the publisher.
Data availability statement
Data in article: research data are available in the published article.
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» https://doi.org/10.2527/1992.70113562x - SOUZA, M.R. de; VARGAS JÚNIOR, F.M. de; SOUZA, L.C.F. de; TALAMINI, E.; CAMILO, F.R. Análise econômica do confinamento de cordeiros alimentados com feno de capim piatã e soja in natura ou desativada. Custos e @gronegócio Online, v.10, p.131-151, 2014.
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VIEIRA, L.V.; SCHMIDT, A.P.; BARBOSA, A.A.; FEIJÓ, J. de O.; BRAUNER, C.C.; RABASSA, V.R.; CORRÊA, M.N.; SCHMITT, E.; DEL PINO, F.A.B. Utilização de taninos como aditivo nutricional na dieta de ruminantes. Arquivos de Ciências Veterinárias e Zoologia da UNIPAR, v.23, e2306, 2020. DOI: https://doi.org/10.25110/arqvet.v23i1cont.2020.8040.
» https://doi.org/10.25110/arqvet.v23i1cont.2020.8040
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Chief editor:
Edemar Corazza
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Edited by:
Mírian Baptista
