Marjorrie Augusto de Souza

Rumen dynamics of neutral detergent fiber in cattle fed low-quality tropical forage and supplemented with nitrogenous compounds

The aim of this work was to evaluate the effects of supplementation with nitrogenous compounds on rumen dynamics of neutral detergent fiber (NDF) in cattle fed low-quality tropical forage. Five crossbred heifers with average live weight of 180 kg and fitted with rumen cannulae were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay, which had crude protein (CP) content of 4.86% of dry matter (DM). The five treatments were proposed in order to raise the CP level of diets to 0, 2, 4, 6, and 8 percentile points above the CP level of the forage. The supplement was a mixture of urea, ammonium sulfate, and albumin (4.5:0.5:1.0, respectively). The experiment was carried out according to a 5 × 5 Latin square design, with five experimental periods. The average CP levels in the diets were: 5.19, 7.11, 8.60, 11.67, and 13.02% on DM basis. The potentially degradable NDF was linearly increased according to the CP levels in diet up to 6.97% of CP. From this point, there was stabilization of estimates (47.87% of NDF). The degradation rate of potentially degradable NDF was linearly increased with the CP levels in diets. The rumen flow of fibrous particles (L) showed a linear-response-plateau pattern according to the CP levels in diets. The plateau (maximum estimate) began on 7.24% of CP. The mean retention time in the rumen and the rumen fill effect of undegradable NDF were affect by the CP levels similarly to L, with plateau (minimum) beginning on 6.90 and 6.97% of CP, respectively.

Evaluation of fecal recovering and long term bias of internal and external markers in a digestion assay with cattle

Objetivou-se estimar a recuperacao total e o vicio de tempo longo das estimativas de excrecao fecal obtidas com os indicadores externos oxido cromico e dioxido de titânio e com os indicadores internos materia seca indigestivel (MSi), fibra em detergente neutro indigestivel (FDNi) e fibra em detergente acido indigestivel (FDAi) em ensaio de digestao com bovinos alimentados com diferentes dietas. Foram utilizados 14 novilhos F1 Red Angus x Nelore, nao-castrados, com idade e peso medios de 12 meses e 287 kg. Os animais foram alimentados com silagem de capim-elefante, silagem de milho ou feno de capim-braquiaria, suplementados ou nao com 20% de mistura concentrada. O experimento foi constituido de dois periodos de 13 dias cada, segundo delineamento em quadrado latino 2 x 2, com agrupamento de sete quadrados. Os animais receberam diariamente 10 g de oxido cromico e 10 g de dioxido de titânio atraves de sonda esofagica. Nao foram observados efeitos de forragem, nivel de concentrado ou de sua interacao sobre as estimativas de recuperacao fecal, tanto dos indicadores internos quanto dos indicadores externos. As estimativas de recuperacao fecal media para o oxido cromico e para o dioxido de titânio foram de 99,50% e 101, 95%, respectivamente. Para os indicadores internos, observou-se recuperacao fecal media de 99,02; 98,87 e 102,07% para MSi, FDNi e FDAi, respectivamente. Em todos os casos, as recuperacoes fecais foram iguais a 100%. Todos os indicadores avaliados podem ser considerados isentos de vicio de tempo longo. Contudo, maior precisao e verificada para as estimativas de excrecao fecal obtidas com indicadores internos.

Simulation of variations in the composition of samples in the evaluation of neutral detergent fiber contents by using cellulose standard in filter bags made from different textiles

The objective of this study was to evaluate the efficiency of using nylon textiles (50 μm), F57 (Ankom®) and non-woven textile (NWT - 100 g/m2) on laboratory evaluation of neutral detergent fiber (NDF) by using quantitative filter paper as purified cellulose standard and by simulating different composition of samples with additions of corn starch, pectin, casein and soybean oil. The quantitative filter paper was processed in a knife mill with a 1-mm screen sieve and the procedures for analyses of NDF contents were performed in a fiber analyzer (Ankom220®). Four experiments were carried out with additions of different ingredients into the filter paper: corn starch added at the levels of 15 or 50%; pectin, 15 or 50%; casein, 10 or 30%; and soybean oil at 0, 5, 10, 15, 25 or 50% of dry matter, respectively. The ratio 20 mg of dry matter/cm2 of surface was followed. When it was relevant, in function of the evaluated treatments, heat-stable α-amylase was used. The use of F57 and NWT resulted in accurate estimates of NDF contents whereas nylon textile caused loss of insoluble fibrous particles, compromising accuracy of the results. For samples containing starch, use of heat-stable α-amylase is recommended in the evaluation of NDF contents. Pectin and casein are completely solubilized by neutral detergent solution. Levels of oil higher than 10% cause overestimation of NDF contents.

Collaborative study to evaluate the mineral content in feeds

Objetivou-se conduzir estudo colaborativo para avaliação do teor de matéria mineral em alimentos em sete laboratórios de análise de alimentos de instituições integrantes do Instituto Nacional de Ciência e Tecnologia de Ciência Animal (INCT-CA). Avaliaram-se seis alimentos: feno de capim-braquiária, cana-deaçúcar, silagem de milho grão, farelo de soja, milho e polpa cítrica. Solicitou-se a cada laboratório que as amostras fossem analisadas por seis dias, consecutivos ou não, sendo realizadas três repetições por amostra por dia de avaliação. Foi observado variação entre laboratórios, dias de análise e efeito de interação de material e laboratório. A variação dos resultados entre laboratórios correspondeu de 33,5 a 78,2% da variação aleatória total. Verificou-se que a repetibilidade representou de 8,5 a 51,6% da reprodutibilidade. Observou-se razões de Horwitz superiores a dois para três dos materiais avaliados. Foi constatado que 42,9% das avaliações apresentaram variações das estimativas em função do dia no qual a análise foi realizada. Também foram verificadas diferenças entre procedimentos de avaliação de matéria mineral em função dos diferentes laboratórios. Os teores de matéria mineral estimados pelos laboratórios participantes deste estudo apresentam baixa reprodutibilidade, o que é agravado pela presença de efeito de interação do material avaliado e do laboratório.

Evaluation of models for prediction of the energy value of diets for growing cattle from the chemical composition of feeds

The objective of this study was to estimate and evaluate the contents of apparently digestible fractions of crude protein, ether extract and non-fibrous carbohydrates, the digestible fraction of the neutral detergent fiber and the content of total digestible nutrients (TDN) from the chemical composition of feeds in growing cattle fed different diets. Fourteen F1 Red Angus × Nellore young bulls with average age and weight of 12 months and 287±36 kg were used. Animals were fed elephant grass silage, corn silage or signal grass hay, with or without supplementation of 200 g concentrate per kg of the total diet. The experiment consisted of two 13-days periods, in which the concentrate supplementation was crossed over animals. The values of digestible fractions and the TDN content observed were obtained based on total collection of feces. Several sub-models applied to the different digestible fractions were assessed and discussed. Estimates of the TDN content in the diet were produced from the combination of sub-models applied to the individual digestible fractions. The TDN content was more efficiently predicted from the sub-models proposed by Detmann et al. (2010) when biological procedures for the estimation of the undegradable fraction of the protein and the potentially degradable fraction of the neutral detergent fiber were considered.