Evaluation in situ digestibility of alfalfa in different grinds and textiles

Avaliação de digestibilidade in situ de alfafa em diferentes moagens e tecidos

Frank Akiyoshi Kuwahara Gilberto Batista de Souza Reinaldo de Paula Ferreira Ciniro Costa Paulo Roberto de Lima Meirelles About the authors

ABSTRACT.

Indigestible fractions of dry matter (iDM) and neutral detergent fiber (iNDF) in the feed of ruminants are mainly estimated by in situ incubation time with regard to particle size and textile types. Samples of alfafa, ground into three particle sizes, were analyzed. Samples, processed in a Willey mill with 1.0; 2.0 and 3.0 mm sieve pores, were conditioned in F57 (Ankon(r)), nonwoven (100 g m-2) and polyester textile bags measuring 4 x 5 cm. Material was divided into 13 incubation periods and 8 replications, and incubated in the rumen of two multiparous cows adapted to a 70:30 diet, roughage:concentrate, respectively, for 288h. iDM and iNDF rates were evaluated sequentially for non-digested percentage and data underwent analysis of variance (ANOVA p < 0.05); means were compared by tukey's test (p < 0.05). Particle size and material employed for incubation affected iDM and iFDN at the initial periods of incubation (p < 0.05).

Keywords:
digestion; neutral detergent fiber; F57; nonwoven textile; polyester textile

RESUMO.

A determinação do tempo de incubação in situ, em relação ao tamanho de partículas e tipos de tecidos, é o aspecto principal sobre as estimativas das frações indigestíveis da matéria seca (MSi) e da fibra em detergente neutro (FDNi) em alimentos para ruminantes. Estudou-se amostra de alfafa, moídas em três tamanhos de partículas. As amostras foram processadas em moinho, com facas e porosidades das peneiras ajustadas a 1,0; 2,0 e 3,0 mm, as amostras foram acondicionadas em sacos F57 (Ankon(r)), tecido não tecido (100 g m-2) e tecido de poliéster, confeccionados na dimensão 4 x 5 cm. Os materiais foram divididos em 13 tempos de incubação e oito repetições, incubadas no rúmen de duas vacas multíparas adaptadas à dieta 70:30, volumoso:concentrado, respectivamente, por tempo total de 288h. Os teores de MSi e FDNi foram avaliados sequencialmente para interpretação das porcentagens de material não digerido, e os dados foram submetidos à análise de variância (ANOVA, p < 0,05), e as médias comparadas posteriormente pelo teste de tukey (p < 0,05). Houve efeito do tamanho de partículas e material utilizado para incubação sobre as estimativas de MSi e FDNi, nos tempos iniciais de incubação (p < 0,05).

Palavras-chave:
digestão; fibra em detergente neutro; F57; tecido não tecido; poliéster

Introduction

High quality forage is a highly important factor for animal production on pasture. Feed quality, however, is related to management, soil fertility and mainly the type of forage grass. Since alfafa is a high quality forage grass, albeit characterized by high digestibility and fast ruminal degradation (Rodrigues, Comeron, & Vilela, 2008Rodrigues, A. A., Comeron, E. A., & Vilela, D. (2008). Utilização de alfafa em pastejo para alimentação de vacas leiteiras. In R. P. Ferreira, J. B. Rassini, A. A. Rodrigues, A. R. Freitas, A. C. Camargo, & A. F. C. Mendon (Eds.). Cultivo e utilização da alfafa nos trópicos (p. 345-378). São Carlos: Embrapa Pecuária Sudeste.), it should be focused upon in assessments for the recuperation of indigestible fractions such as internal indicators, inconsistencies of results for incubation time and material used in in situ assays, as already analyzed by Detmann et al. (2007Detmann, E., Souza, A. L., Garcia, R., Valadares Filho, S. C., Cabral, L. S., & Zervoudakis, J. T. (2007). Avaliação do vício de "tempo longo" de indicadores internos em ensaios de digestão com ruminantes. Arquivo Brasileiro de Medicina Veterinária e Zootecnia591), 182-188.) and Kuwahara Souza, Soares, Costa, and Meirelles (2015Kuwahara, F. A., Souza, G. B., Soares, V. F., Costa, C., & Meirelles, P. R. L. (2015). Estimated of in situ digestibility and fibrous compounds in ruminant feeds. Acta Scientiarum Animal Sciences, 37(3), 259-264.).

The insoluble and indigestible fibrous fraction of feed, specifically indigestible neutral detergent fiber (iNDF), is extensively used due to preciseness in results (Piaggio, Prates, Pires, & Ospina, 1991Piaggio, L. M., Prates, E. R., Pires, F. F., & Ospina, H. (1991). Avaliação das cinzas insolúveis em ácido, fibra detergente ácido indigestível e lignina em detergente ácido indigestível como indicadores internos da digestibilidade. Revista da Sociedade Brasileira de Zootecnia20(3), 306-312.). According to Van Soest (1994Van Soest, P. J. (1994). Nutritional ecology of the ruminant. (2a ed., p. 476). London: Constock Publishing Associates, New York: Cornell University Press.), the indigestible fraction of feed for internal intake indexes is a highly promising tool in studies on animal nutrition. Berchielli, Andrade and Furlan (2000Berchielli, T. T., Andrade, P., & Furlan, C. L. (2000). Avaliação de indicadores internos em ensaios de digestibilidade. Revista Brasileira de Zootecnia29(3), 830-833.) report that iNDF is usually employed in estimates such as fecal production, coefficients of digestibility, food ingestion and flow of nutrients through the gastrointestinal tract of the animals.

Further, incubation time and material used to condition the samples in the rumen are basic factors to standardize methodology for the in situ determination of the indigestible fraction. According to Mertens (1993Mertens, D. R. (1993). Rate and extent of digestion. In J. M. Forbes., & J. France (Eds.). Quantitative aspects of ruminant digestion and metabolism (p. 13-51), CAB International, Wallingfor, UK.), the indigestible fraction is an asymptotic concept, or rather, it is truly measured in procedures performed in an infinite scale of time. Contrastingly, in their work on the dynamics of ruminal degradation of feed produced in tropical and non-tropical situations, Detmann et al. (2008Detmann, E., Valadares Filho, S. C., Pina, D. S., Henriques, L. T., Paulino, M. F., Magalhães, K. A., & Chizzotti, M. L. (2008). Prediction of the energy value of cattle diets based on the chemical composition of the feeds under tropical conditions. Animal Feed Science and Technology 143(1-4), 127-147.) insist that the definition is inefficient for tropical conditions. In fact, in situ procedures are based on finite scales of times, assuming a relatively high temporal rate to materialize the asymptotic concept.

Nylon, the standard material for in situ incubation procedures (Nocek, 1997Nocek, J. E. (1997). In situ and other methods to estimate ruminal protein and energy digestibility: a review. In J. C. Teixeira (Ed.). Digestibilidade em ruminantes (p. 197-240). Lavras, MG: Faepe.), showed ambiguous rates in estimates of in situ indigestible residues for 240h, due to particle loss through the pores of nylon bags (Piaggio et al., 1991Piaggio, L. M., Prates, E. R., Pires, F. F., & Ospina, H. (1991). Avaliação das cinzas insolúveis em ácido, fibra detergente ácido indigestível e lignina em detergente ácido indigestível como indicadores internos da digestibilidade. Revista da Sociedade Brasileira de Zootecnia20(3), 306-312.) and to the integrity of the material after procedures to determine iDM and iNDF (Valente et al., 2011Valente, T. A. P., Detmann, E., Valadares Filho, S. C., Cunha, M., Queiroz, A. C., & Sampaio, C. B. (2011). In situ estimation of indigestible compounds contents in cattle feed and feces using bags made from different textiles. Revista Brasileira de Zootecnia, 40(3), 666-675.). The Ankom(r) system, synthetic fiber bags insoluble in acid and neutral medium, has been used for more precise and favorable results (Berchielli, Sader, Tonani, Paziani, & Andrade, 2001Berchielli, T. T., Sader, A. P. O., Tonani, F. L.; Paziani, S. D. F., & Andrade, P. D. (2001). Avaliação da determinação da fibra em detergente neutro e da fibra em detergente ácido pelo sistema ANKOM. Revista Brasileira de Zootecnia, 305), 1572-1578.). However, high costs in routine feed analysis in the system shifted usage towards nonwoven textile (NWT), weight 100 g m-2, as an alternative (Casali et al., 2009Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira J. C., Cunha, M., Detmann, K. S. C., & Paulino, M. F. (2009). Estimação de teores de componentes fibrosos em alimentos para ruminantes em sacos de diferentes tecidos. Revista Brasileira de Zootecnia, 38(1), 130-138.).

However, there is a decrease in the integrity of the material in long incubation periods, even though no difference exists when compared to the Ankom(r) system (Valente et al., 2011Valente, T. A. P., Detmann, E., Valadares Filho, S. C., Cunha, M., Queiroz, A. C., & Sampaio, C. B. (2011). In situ estimation of indigestible compounds contents in cattle feed and feces using bags made from different textiles. Revista Brasileira de Zootecnia, 40(3), 666-675.). Since preciseness of results is required, Kuwahara et al. (2015Kuwahara, F. A., Souza, G. B., Soares, V. F., Costa, C., & Meirelles, P. R. L. (2015). Estimated of in situ digestibility and fibrous compounds in ruminant feeds. Acta Scientiarum Animal Sciences, 37(3), 259-264.) enhance the existence of variability in the quality of the material on the Brazilian market.

Results by Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.) showed different critical times (hours) of incubation for feeds with regard to indigestible dry matter (iDM): 170.8 (elephant grass - 73.13% NDF); 139.1 (Brachiaria hay - 77.31% NDF); 137.5 (sugarcane - 50.70% NDF); 207.8 (corn silage - 3.0 mm - 51.07% NDF); 217.2 (corn straw - 89.84% NDF). In fact, results reveal that rates of fibrous components of feed may be directly related to incubation time. Although Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.) reported difference in incubation time for sugarcane only, with different grindings, Kuwahara et al. (2015Kuwahara, F. A., Souza, G. B., Soares, V. F., Costa, C., & Meirelles, P. R. L. (2015). Estimated of in situ digestibility and fibrous compounds in ruminant feeds. Acta Scientiarum Animal Sciences, 37(3), 259-264.) registered that alfafa ground at 0.5 mm (37.84% NDF) overestimated iDM and iMDF rates. According to Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.), 3.0 mm grindings may cause lack of precision in results, attributing the smallest specific surface for microbial activities (Nocek, 1997Nocek, J. E. (1997). In situ and other methods to estimate ruminal protein and energy digestibility: a review. In J. C. Teixeira (Ed.). Digestibilidade em ruminantes (p. 197-240). Lavras, MG: Faepe.). At the same time, it should be underscored that a greater particle size may favor the sample's non-homogeneity with regard to the amount of incubated material (20 mg cm-2), especially in roughage, corroborating the lack of precision in results. The standardization of the sample preparation with 2 mm sieves is recommended for in situ protocols (Hvelplund & Weisbjerg, 2000Hvelplund, T., Weisbjerg, M. R. (2000). In situ techniques for the estimation of protein degradability and postrumen availability. In D. I. Givens, E. Owen, R. F. E. Axford and H. M. Omed (Eds.). Forage evaluation in ruminant nutrition (p. 233-258). London, UK: CAB International.; National Research Council [NRC], 2001National Research Council (NRC). (2001). Nutrient requirements of dairy cattle (7a ed., p. 381). Washington, DC: Academic Press.)

Current assay therefore evaluates the types of material for the conditioning of samples in the rumen of animals, particle size and incubation time on the estimates of indigestible compounds in Dry Matter (iDM) and indigestible Neutral Detergent Fiber (iNDF) in alfafa.

Material and methods

Current experiment was conducted at the Laboratory of Animal Nutrition of Embrapa Pecuária Sudeste, São Carlos, São Paulo State, Brazil. Samples of alfafa (Medicago sativa L.), harvested at the Embrapa unit during the summer, at the phenological stage in which 10% of the plants featured floral buds, were used. Samples, divided into three sub-samples, were pre-dried in a forced air buffer at 60oC for 72 hours, following Silva & Queiroz (2002Silva, D. J., Queiroz, A. C. (2002). Análise de alimentos: métodos químicos e biológicos (3a ed., p. 235). Viçosa, MG: Editora UFV.), and ground in a Wiley mill. Treatments consisted of three grinding processes, with adjustment of knives and sieve porosity (1.0, 2.0, 3.0 mm), three types of materials to condition the samples in the animal's rumen (Ankom(r) F57, NWT and nylon) and 13 incubation times at 24-h intervals. A sub-sample of approximately 300 g was removed and the fractioning of particle sizes was quantified in each grinding treatment. A vibration sieve (Retsch(r) AS 200), with a set of 9 sieves, was employed at a 20-min. sieving period.

Samples were analyzed for dry matter (DM), mineral matter (MM) and crude protein (CP) rates, following Silva & Queiroz (2002Silva, D. J., Queiroz, A. C. (2002). Análise de alimentos: métodos químicos e biológicos (3a ed., p. 235). Viçosa, MG: Editora UFV.), given in Table 1. The chemical composition of alfafa comprised 37.8% neutral detergent fiber (NDF), 30.6% acid detergent fiber (ADF) and 7.4% lignin, following methodology by Van Soest and Robertson (1985Van Soest, P. J., & Robertson, J. B. (1985). Analysis of forages and fibrous foods (p. 202). Ithaca, New York: Cornell University. ).

Table 1
Chemical composition of alfafa in different grindings.

Alfafa samples were weighed and conditioned in F57 (Ankom(r)), nonwoven textile (NWT 100 g m-2) and nylon textile (50 (m) bags to evaluate rates of indigestible dry matter (iDM) and indigestible neutral detergent fiber (iNDF). NWT and nylon bags measuring 4 x 5 cm were made. Samples were conditioned in all bags with 20 mg of DM per cm2 (Nocek, 1997Nocek, J. E. (1997). In situ and other methods to estimate ruminal protein and energy digestibility: a review. In J. C. Teixeira (Ed.). Digestibilidade em ruminantes (p. 197-240). Lavras, MG: Faepe.).

Experimental design consisted of randomized blocks with a 3 x 3 x 13 factorial design (three types of grinding; three types of material; 13 incubation intervals, with eight replications, involving two animals. Bags were incubated in the rumen of two cross-breed Holstein x Jersey cows fed on a 70:30 (roughage: concentrate) diet. Incubation period totaled 288 hours, with 24-h intervals, for the composition of each incubation time, with 13 periods: 0, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, 264, and 288 hours. Samples were analyzed directly for NDF rates at zero time for the respective materials and grindings. After each incubation time, the bags were removed, washed in running water till total whitening, dried at 105ºC for three hours, conditioned in a dryer, cooled and weighed on an analytic scale to determine non-digestible dry matter. Further, extraction on the same material and textile used for incubation was undertaken with neutral detergent solution (Mertens, 2002Mertens, D. R. (2002). Gravimetric determination of amylase-treated neutral detergent fiber in feeds with refluxing in beaker or crucibles: collaborative study. Journal of AOAC International85(6), 1217-1240.) by Ankom(r) fiber analyzer equipment (American Oil Chemists' Society [AOCS], 2009American Oil Chemists' Society (AOCS). (2009). Approved Procedure Ba 6a-05; ANKOM Technology Method 10: Crude Fiber Analysis in Feeds - Filter Bag Technique (for A2000 and A2000I). Retrieved October 5, 2015, from http://www.aocs.org
http://www.aocs.org...
).

Data were submitted to analysis of variance (Anova, p < 0.05) and averages were compared by tukey's test (p < 0.05) with Statistical Analysis System (SAS, 2003Statistical Analysis Systems (SAS). (2003). SAS/STAT Use's guide. Release 9.1 Cary, NC: SAS Institute Inc.).

Results and discussion

Figure 1 shows size particles of each grinding. All treatments provided particle size less than expected. Most sieves and knives adjusted to 3.0 mm had particle sizes ranging between 0.5 and 1.5 mm, with significant dispersion when compared to 1.0 and 2.0 mm grinding. Greater homogeneity in particle size was better for the two treatments. Greater preciseness should be expected for laboratory analyses, as Table 1 shows, where CP rates were more exact with more intense grinding, also reported by Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.). These authors added that grinding with 2.0-mm-pore sieve may be suggested for the standardization of samples in in situ analyses (NRC, 2001National Research Council (NRC). (2001). Nutrient requirements of dairy cattle (7a ed., p. 381). Washington, DC: Academic Press.).

According to Ørskov, (2000Ørskov, E. R. (2000). The in situ technique for the estimation of forage degradability in ruminants. In D. I. Givens, E. Owen R. F. E. Axfordand H. M. Omed (Eds.), Forage evaluation in ruminant nutrition (p. 175-188). London, UK: CAB International ), the indigestible fraction is the exclusive characteristic of the substrate and not of the fermentation medium or particularity of the experimental material. Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.) did not report possible loss of the particle related to textile porosity, with the exception of sugarcane where the indigestible fraction was higher in 3 mm (32.07%) when compared to 2mm (28.63%) and 1 mm (28.51%). The authors also registered that if real loss of particle occurred, iNDF and iADF rates must also be affected, which was not observed by the authors. They also reported that iDM fraction is made up of essentially insoluble components, similar to the iDF and iADF fractions. Although data in current experiment corroborate the theory by Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.), Kuwahara et al. (2015Kuwahara, F. A., Souza, G. B., Soares, V. F., Costa, C., & Meirelles, P. R. L. (2015). Estimated of in situ digestibility and fibrous compounds in ruminant feeds. Acta Scientiarum Animal Sciences, 37(3), 259-264.) reported that more intense grindings may overestimate iDM and iNDF rates at an average of 6.57% for alfafa when grinding shifted from 1.5 mm to 0.5 mm for a fixed period of 240 hours.

Figure 1
Quantity of sample (%) per sieve (mm) in different grindings for alfafa. Amount of fractioning of particle sizes per vibratory sieve Retsch(r) AS 200.

When the concept by Mertens (1993Mertens, D. R. (1993). Rate and extent of digestion. In J. M. Forbes., & J. France (Eds.). Quantitative aspects of ruminant digestion and metabolism (p. 13-51), CAB International, Wallingfor, UK.), previously discussed, is taken into consideration, coupled to the description by Detmann et al. (2008Detmann, E., Valadares Filho, S. C., Pina, D. S., Henriques, L. T., Paulino, M. F., Magalhães, K. A., & Chizzotti, M. L. (2008). Prediction of the energy value of cattle diets based on the chemical composition of the feeds under tropical conditions. Animal Feed Science and Technology 143(1-4), 127-147.) as a slightly precise concept, results of current analysis (Figure 2 and Tables 2 and 3) reveal that the nylon textile in the three grindings had lower iDM and iNDF rates when compared to other treatments (p < 0.05) in the initial period of incubation. After 96 hours of incubation, all materials and grindings are likely to have similar rates where the differences between material, times and grinding may be due to the contamination of F57 and TNT textiles, as reported by Casali et al. (2009Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira J. C., Cunha, M., Detmann, K. S. C., & Paulino, M. F. (2009). Estimação de teores de componentes fibrosos em alimentos para ruminantes em sacos de diferentes tecidos. Revista Brasileira de Zootecnia, 38(1), 130-138.) and Kuwahara et al. (2015Kuwahara, F. A., Souza, G. B., Soares, V. F., Costa, C., & Meirelles, P. R. L. (2015). Estimated of in situ digestibility and fibrous compounds in ruminant feeds. Acta Scientiarum Animal Sciences, 37(3), 259-264.).

At zero time, direct extraction in neutral detergent solution in Ankon(r) fiber analyzer, nylon textile in 1.0 and 2.0 mm grindings overestimated NDF rates (Table 3) where, according to Huhtanen Kaustell, and Jaakkola (1994Huhtanen, P., Kaustell, K., & Jaakkola, S. (1994). The use of internal markes to predict total digestibility and duodenal flow of nutrients in cattle given six different diets. Animal Feed Science and Technology, 48(3-4), 211-227.), the exactness of results and possible loss of particle are compromised, as reported by Casali et al. (2009Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira J. C., Cunha, M., Detmann, K. S. C., & Paulino, M. F. (2009). Estimação de teores de componentes fibrosos em alimentos para ruminantes em sacos de diferentes tecidos. Revista Brasileira de Zootecnia, 38(1), 130-138.). Results in current assay corroborate these theories where, despite less intense grindings in treatments with 3.0 mm particles, also demonstrated particles lower than 0.5 mm (Figure 1) which, besides triggering the loss of particles, also affects the instability of results. Although textile integrity was not evaluated, Valente et al. (2011Valente, T. A. P., Detmann, E., Valadares Filho, S. C., Cunha, M., Queiroz, A. C., & Sampaio, C. B. (2011). In situ estimation of indigestible compounds contents in cattle feed and feces using bags made from different textiles. Revista Brasileira de Zootecnia, 40(3), 666-675.) report the decrease of resistance to NWT and Nylon tension when compared to F57, after the determination of iDM and iNDF where the possible influence of results in reuse is related.

When Casali et al. (2009Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira J. C., Cunha, M., Detmann, K. S. C., & Paulino, M. F. (2009). Estimação de teores de componentes fibrosos em alimentos para ruminantes em sacos de diferentes tecidos. Revista Brasileira de Zootecnia, 38(1), 130-138.) compared the integrity of the materials nylon, Ankom(r) and nonwoven textile by electronic photomicrographs, they failed to report any difference in the integrity of pre- and post-incubation nylon. According to these authors, NWT and F57 provided structures that might limit the introduction of microorganisms and the exit of non-degraded fibrous particles. According to Udén, Parra and Van Soest (1974Udén, P., Parra, R., & Van Soest, P. J. (1974). Factors influencing reliability of the nylon bag technique. Journal of Dairy Science57(suppl 1), p. 358.), pore reduction may decrease the elimination of gases from fermentation, with a lower degradation of NDF which may explain greater iNDF estimates (Casali et al., 2009Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira J. C., Cunha, M., Detmann, K. S. C., & Paulino, M. F. (2009). Estimação de teores de componentes fibrosos em alimentos para ruminantes em sacos de diferentes tecidos. Revista Brasileira de Zootecnia, 38(1), 130-138.). However, Lindberg and Knutsson (1981Lindberg, J. E., & Knutsson, P.G. (1981). Effect of bag pore size on the loss of paniculate matter and on the degradation of cell wall fibre. Agriculture and Environment, 6(2-3), 171-182.), quoted by Udén and Van Soest (1984Udén, P., Van Soest, P .J. (1984). Investigation of the in situ bag technique and a comparison of the fermentation in heifers, sheep, ponies and rabbits. Journal of Animal Science58(1), 213-221.), evaluated the removal of particles in in situ incubation procedures in textile with different porosities (5, 10 and 20 μm) and verified less fibrous residues for the reduction of porosity in the initial incubation periods. However, after 24 hours of incubation, the authors reported that degradation curves converged, while residues were considered similar for all types of porosity after 72 hours. Results corroborate a behavior similar to current analysis (Tables 2 and 3), contrastingly to Huhtanen et al. (1994Huhtanen, P., Kaustell, K., & Jaakkola, S. (1994). The use of internal markes to predict total digestibility and duodenal flow of nutrients in cattle given six different diets. Animal Feed Science and Technology, 48(3-4), 211-227.) and Casali et al. (2009).

Casali et al. (2009Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira J. C., Cunha, M., Detmann, K. S. C., & Paulino, M. F. (2009). Estimação de teores de componentes fibrosos em alimentos para ruminantes em sacos de diferentes tecidos. Revista Brasileira de Zootecnia, 38(1), 130-138.), Valente et al. (2011Valente, T. A. P., Detmann, E., Valadares Filho, S. C., Cunha, M., Queiroz, A. C., & Sampaio, C. B. (2011). In situ estimation of indigestible compounds contents in cattle feed and feces using bags made from different textiles. Revista Brasileira de Zootecnia, 40(3), 666-675.) and Kuwahara et al. (2015Kuwahara, F. A., Souza, G. B., Soares, V. F., Costa, C., & Meirelles, P. R. L. (2015). Estimated of in situ digestibility and fibrous compounds in ruminant feeds. Acta Scientiarum Animal Sciences, 37(3), 259-264.) did not report significant differences between the textiles Ankom(r) and NWT, with the later coming up as an alternative. According to Detmann et al. (2008Detmann, E., Valadares Filho, S. C., Pina, D. S., Henriques, L. T., Paulino, M. F., Magalhães, K. A., & Chizzotti, M. L. (2008). Prediction of the energy value of cattle diets based on the chemical composition of the feeds under tropical conditions. Animal Feed Science and Technology 143(1-4), 127-147.), different materials may require distinct protocols to estimate the indigestible fraction of DM, NDF and ADF, confirmed by Casali et al. (2008Casali, A. O., Detmann, E., Valadares Filho, S. C., Pereira, J. C., Henriques, L. T., Freitas, S. G., & Paulino, M. F. (2008). Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia, 37(2), 335-342.) in the critical periods between indexes and feed.

Corrêa, Magalhães and Siqueira (2012Corrêa, D. S., Magalhães, R. T., Siqueira, D. B. (2012). In situ dry matter and fiber fraction degradability of the Mineirão stylos. Acta Scientiarum Animal Sciences342), 203-207.) evaluated the degradability of dry matter and the fibrous fraction of the leguminous Stylozanthes guianensis using 5.0 mm grindings and nylon bags (50 (m) and reported that degradability rates remained constant after 48 hours of incubation, with a 75.70% effective degradability for DM, 59.01% for NDF and 76.81% for ADF. Stability after this period was also reported by Santos et al. (2012Santos, S., Santos-Cruz, C. L., Rocha, J. B., Pires, A. J. V., Santos, I. P. A., Lima, T. R., & Junqueira, R. S. (2012). Degradação ruminal da silagem de capim elefante com diferentes componentes de algarroba. Revista Brasileira de Saúde e Produção Animal13(1), 123-136. ) when they used silage with elephant grass (Pennisetum purpureum Schum.), nylon textile (50 (m) and 2.0 mm grinding. Figure 2 demonstrates similarity in results in current analysis when nylon was employed.

Similarity in iDM and iNDF rates at the last period of incubation suggests that differences in initial times for nylon may be related to high rates of ruminal degradation of alfafa plus a greater fluidity of the material when compared with F57 and TNT. In fact, they provide a slower rate in bacterial activity in the degradation of NDF as they limit the exit of degraded material. Undesired materials after the incubation process may be eliminated in the fiber extraction process, with inconsistent rates.

Figure 2
Mean rates of indigestible dry matter - iDM (%) and indigestible neutral detergent fiber - iNDF (%) in different grindings, materials and incubation times.

Inconsistency of data in the literature for the standardization for in situ procedures and internal consumption markers suggests further research for incubation time, material and textile to condition material in the rumen. Since nylon requires different grindings and F57 has high costs for routine lab tests, NWT may be an alternative due to its availability on the Brazilian market and to the quality of the material for preciseness in results. However, caution should be taken in the use of NWT in in situ procedures.

Conclusion

Nylon inconsistencies to determine dry matter and indigestible fibrous fraction of food recommends F57 textile (Ankom(r)) to determine indigestible fiber rates in neutral detergent by the in situ technique due to exactness of results. Since F57 textile is expensive for routine lab tests, the nonwoven textile (100 g m-2) may be its substitute due to estimates similar to those of F57. Since several divergences are extant in comparative studies, further research work on the material must be accomplished for its use so that standardization of results may be obtained.

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Publication Dates

  • Publication in this collection
    Mar 2016

History

  • Received
    13 Aug 2015
  • Accepted
    09 Oct 2015
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