Comparison of laboratory methods to assess fiber contents in feedstuffs / Comparación de métodos de laboratorio para determinar el contenido de fibra en alimentos para animales / Comparação de metodologias laboratoriais para determinação de fibras em alimentos

Summary Background: the conventional method of fiber analysis using neutral detergent fiber (NDF) and acid detergent fiber (ADF) was proposed by Peter Van Soest. The main advantage of this method is the precision of results; however, reagents are costly and laboratory work requires long runtime and labor. Objective: to compare analytical data from different methodologies used to assess NDF and ADF contents. Methods: means obtained with the conventional method were compared through Dunnett's test (α=5%) with values from alternative methods using autoclave as the digester system. A completely randomized design in a 4 x 2 factorial arrangement was used. Results: NDF content through alternative methods was assessed for Tifton 85 hay, babassu meal and sugarcane, whereas ADF was only determined for babassu meal. NDF and ADF did not differ (p(0.05) between non-sequential or sequential analysis for all the feedstuffs and methods studied, except for ADF in corn silage. Conclusion: alternative methodologies allow reducing operating costs and time but lack uniformity and accuracy for analyzing ADF in corn silage.

Resumen Antecedentes: la determinación de los valores de fibra detergente neutra (FDN) y fibra detergente ácida (FDA) es de gran importancia en la nutrición animal, siendo el método tradicional de análisis el propuesto por Van Soest. Este método presenta como ventaja principal la precisión de los resultados, sin embargo la rutina de laboratorio en su ejecución implica mucho tiempo debido a sus etapas manuales, además de ser un método de alto costo que genera considerables proporciones de residuos químicos. Objetivo: evaluar diferentes metodologías propuestas para la análisis de las FDN y FDA mediante la medición de los datos analíticos. Métodos: las medias obtenidas por el método tradicional fueron comparadas con las medias de métodos alternativos que usan una autoclave como sistema digestor por el test de Dunnette (α=5%). Un diseño completamente aleatorio, en un diseño factorial 4x2 fue adoptado. Resultados: los métodos alternativos fueron recomendadas para las determinaciones de FDN por el heno de Tifton 85, salvado de harina de babasú y caña de azúcar, mientras que las determinaciones de los valores de FDA apenas para el salvado de harina de babasú. Los resultados de los análisis de FDN y FDA no fueron significativamente diferentes (p(0.05) entre los análisis no secuencial y secuencial, en todos los alimentos y métodos estudiados, a excepción de la determinación de FDA en el ensilaje de maíz. Conclusión: las metodologías alternativas permitieron ganancias significativas con la reducción de costos operacionales y del tiempo de análisis, pero sin uniformidad en la precisión de los análisis involucrados.

Resumo Antecedentes: as determinações dos teores de fibra em detergente neutro (FDN) e em fibra em detergente ácido (FDA) são de extrema importância na nutrição animal, tendo como método convencional de análise o proposto por Van Soest. Esse método apresenta como principal vantagem a precisão dos resultados, no entanto, a rotina laboratorial da sua execução demanda muito tempo por possuir etapas manuais, além do que é um método de custo elevado e que gera resíduos químicos em proporções consideráveis. Objetivo: avaliar diferentes metodologias propostas para análise da FDN e FDA, através da verificação dos dados analíticos. Métodos: as médias obtidas pelo método convencional foram comparadas com as médias de métodos alternativos que utilizam a autoclave como sistema digestor, pelo teste de Dunnette (α=5%). O delineamento adotado foi o inteiramente casualizado, em um esquema fatorial 4x2. Resultados: os métodos alternativos foram recomendados para determinação de FDN no feno de Tifton 85, farelo de babaçu e cana-de-açúcar, enquanto para as determinações dos teores de FDA, apenas no farelo de babaçu. A precisão observada nas análises dos teores de FDN e FDA não diferiram significativamente (p(0.05) quanto a análise não sequencial e sequencial, em todos os alimentos e métodos estudados, com exceção da determinação de FDA na silagem de milho. Conclusão: as metodologias alternativas permitiram ganhos significativos com a redução dos custos operacionais e do tempo da análise, mas sem uniformidade na precisão das análises desenvolvidas.

Parameters of fermentation and rumen microbiota of Nellore steers fed with different proportions of concentrate in fresh sugarcane containing diets.

The objective of this study was to evaluate the effect of a fresh sugarcane-based diet and different roughage-to-concentrate ratios (70:30, 60:40, 40:60 and 20:80) on the rumen microbiota associated with rumen fermentation parameters and the intake and apparent digestibility of nutrients in Nellore steers. Eight rumen-cannulated Nellore steers (331 ± 8 kg BW) were distributed in a double 4 × 4 Latin square design balanced for the control of the residual effect. The ruminal pH decreased (p < 0.01) and the concentrations of N-NH3, isovaleric and valeric acids increased linearly (p < 0.05) with an increase dietary concentrate level. Furthermore, an increased concentrate proportion reduced the population of Fibrobacter succinogenes and Ruminococus flavefaciens (p < 0.01) and increased the population of Selenomonas ruminantium and Megasphaera elsdenii (p < 0.01). The protozoa count revealed a predominance of the genus Entodinium. The synthesis of microbial N [g/d] and the efficiency of microbial synthesis [g of microbial N/kg of organic matter apparently digested in the rumen] increased as the proportion of concentrate was increased (p < 0.05). Therefore, it can be concluded that an increasing proportion of concentrate in sugarcane-containing diets enhances the synthesis of microbial protein and does not alter the fibre digestibility, although the population of fibre fermenting bacteria was reduced.

Effect of different levels of concentrate on ruminal microorganisms and rumen fermentation in Nellore steers.

The aim of this study was to investigate the effect of different dietary levels of concentrate on feed intake, digestibility, ruminal fermentation and microbial population in steers. Eight Nellore steers fitted with ruminal cannulas were used in a double 4 × 4 Latin square design experiment. The dietary treatments consist of four different proportions of concentrate to roughage: 30:70, 40:60, 60:40 and 80:20% in the dry matter, resulting in Diets 30, 40, 60 and 80, respectively. The roughage was corn silage, and the concentrate was composed of corn, soybean meal and urea. Apparent digestibility of organic matter and crude protein showed a linear association with concentrate proportion (p = 0.01), but the increased concentrate levels did not affect the digestibility of fibre. The lowest ruminal pH-values were observed in animals fed with Diet 80, remaining below pH 6.0 from 6 h after feeding, while in the other diets, the ruminal pH was below 6.0 not before 12 h after feeding. After feeding Diet 80, the ammonia concentration in the rumen was significantly the highest. Higher dietary concentrate levels resulted in a linear increase of propionic acid concentrations, a linear reduction of the ratio acetic acid to propionic acid (p < 0.01) and a linear increased synthesis of microbial nitrogen (p < 0.001). The predicted production of methane was lower in diets with greater amounts of concentrate (p = 0.032). The population of methanogens, R. flavefaciens and R. albus decreased with higher concentrate levels, while the population of S. ruminantium increased (p < 0.05). The results indicate that greater amounts of concentrate do not decrease ruminal pH-values as much as expected and inhibit some cellulolytic bacteria without impairing the dry matter intake and fibre digestibility in Nellore steers.

Effect of Lipid Sources with Different Fatty Acid Profiles on Intake, Nutrient Digestion and Ruminal Fermentation of Feedlot Nellore Steers.

The present study was conducted to determine the effect of lipid sources with different fatty acid profiles on nutrient digestion and ruminal fermentation. Ten rumen and duodenal fistulated Nellore steers (268 body weight±27 kg) were distributed in a duplicated 5×5 Latin square. Dietary treatments were as follows: without fat (WF), palm oil (PO), linseed oil (LO), protected fat (PF; Lactoplus), and whole soybeans (WS). The roughage feed was corn silage (600 g/kg on a dry matter [DM] basis) plus concentrate (400 g/kg on a DM basis). The higher intake of DM and organic matter (OM) (p<0.001) was found in animals on the diet with PF and WF (around 4.38 and 4.20 kg/d, respectively). Treatments with PO and LO decreased by around 10% the total digestibility of DM and OM (p<0.05). The addition of LO decreased by around 22.3% the neutral detergent fiber digestibility (p = 0.047) compared with other diets. The higher microbial protein synthesis was found in animals on the diet with LO and WS (33 g N/kg OM apparently digested in the rumen; p = 0.040). The highest C18:0 and linolenic acid intakes occurred in animals fed LO (p<0.001), and the highest intake of oleic (p = 0.002) and C16 acids (p = 0.022) occurred with the diets with LO and PF. Diet with PF decreased biohydrogenation extent (p = 0.05) of C18:1 n9,c, C18:2 n6,c, and total unsaturated fatty acids (UFA; around 20%, 7%, and 13%, respectively). The diet with PF and WF increased the concentration of NH3-N (p<0.001); however, the diet did not change volatile fatty acids (p>0.05), such as the molar percentage of acetate, propionate, butyrate and the acetate:propionate ratio. Treatments PO, LO and with WS decreased by around 50% the concentration of protozoa (p<0.001). Diets with some type of protection (PF and WS) decreased the effects of lipid on ruminal fermentation and presented similar outflow of benefit UFA as LO.

Lipid Sources with Different Fatty Acid Profile Alters the Fatty Acid Profile and Quality of Beef from Confined Nellore Steers.

The present study was conducted to determine the effects of lipid sources with different fatty acids profile on meat fatty acids profile and beef quality traits of Nellore. A total of 45 Nellore animals with an average initial body weight of 419±11 kg (at 15±2 mo) were distributed in a completely randomized design consisting of 5 treatments and 9 replicates. The roughage feed was maize silage (600 g/kg on a dry matter [DM] basis) plus concentrate (400 g/kg on a DM basis). The dietary treatments were as follows: without fat (WF), palm oil (PO), linseed oil (LO), protected fat (PF), and soybean grains (SG). No effects of lipid sources were observed (p>0.05) on beef color, pH, water-holding capacity, and sarcomere length. Beef from cattle fed PO had greater shear-force values (p<0.05) compared to beef from cattle fed WF. Deposition of main unsaturated fatty acids (oleic, linoleic, and linolenic) was greater in treatments WF, SG, and LO, respectively, while the values of conjugated linoleic acid (CLA) were greater when animals were fed LO. The inclusion of LO in the diet enhances the concentration of CLA in longissimus muscle and subcutaneous fat besides improving the atherogenicity index and elongase activity. As such, LO can be used with the aim to improve the quality of beef from confined Nellore cattle. Conversely, the use of PO is not recommended since it may increase the concentration of undesirable unsaturated fatty acids in muscle and subcutaneous fat, shear-force and the atherogenicity index.