Passage rates and ruminal degradation kinetics in Holstein calves fed diets with different concentrate levels

[摘要] - This work was conducted to evaluate the effects of different concentrate levels on the liquid passage rates, using Co-EDTA, and particulate, using ytterbium chloride and Cr-mordant, and the in situ ruminal degradation kinetics of dry matter (DM) and crude protein (CP). Five rumen and abomasum fistulated bull Holstein calves, with an initial average age of 5.8±0.7 months and initial average of 107.4±11.0 kg LW were allotted to a 5x5 Latin square design (treatment x period). The animals were housed in individual stalls and full fed diets (DM basis) containing 30.0, 45.0, 60.0, 75,0 and 90.0% of concentrate. The diets were based on coast-cross grass hay as forage and soybean meal an corn ground grain in the concentrate. The passage rate of fluids showed a quadratic behavior, with the maximum value of 9.73%/h, with the 61.69% of concentrate in the diet. The particulate passage rate of the soybean meal in the reticulum-rumen linearly decreased, while the concentrate levels in the diets did not affect the passage rate in proximal cecum-colon. The concentrate levels in the diet did not affect the passage rates of the coast-cross grass hay in the reticulum-rumen and in the proximal cecum-colon. The effective degradation of the DM of the soybean meal was not affected, while those of the corn ground grain increased and coast-cross grass hay linearly decreased, respectively. The effective degradation of the CP of the soybean meal and coast-cross grass hay did not vary, however, that of the corn ground grain linearly increased as the dietary concentrate levels increased.

[学科分类] 兽医学

[关键词] Holstein calves;ruminal degradation;concentrate levels;passage rate     IntroduçãoA taxa de passagem ou de trânsito refere-se ao fluxo de resíduos não-digeridos através do trato digestório; o fluxo ruminal inclui;além da fibra indigestível;bactérias e outras frações não-degradadas do alimento;sendo que a composição e o volume da dieta são variáveis externas que influenciam a digestão;a taxa de digestão e a reciclagem do conteúdo ruminal (VAN SOEST;1994)