Desempenho e desenvolvimento dos ÃrgÃos digestivos de cordeiros santa inÃs, alimentados com dietas contendo diferentes nÃveis de fibra / Performance and development of the digestive tract of Santa InÃs lambs fed with diets containing different levels of fiber.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This study was carried out at the Ovine Production Sector of the Federal University of Lavras-MG, to evaluate the effects of different levels of forage neutral detergent fiber on the consumption, digestibility, feed conversion, weight gain and development of the digestive tract of Santa InÃs lambs in four different development phases. The suckling phase (up to 55 days), post weaning phase (55 to 83 days), growing phase (83 to 123 days) and finishing phase (123 to 173 days). 68 male lambs were used which were divided in four groups. Each group received a diet with different neutral detergent fiber levels (fNDF), as follows: diet A - 8,67% fNDF, diet B - 17,34% fNDF, diet C - 26,01% fNDF and diet D - 34,68% fNDF. Four animals of each diet were slaughtered at 43, 83, 123 and 173 days of age, as well as four references animals which were slaughtered at birth. The intake of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), digestible protein (DP), crude energy (CE), digestible energy (DE) and metabolizable energy (ME) were evaluated. Four digestibility trials were carried out (at the 69, 105, 137 and 161 days of age) to determine apparent digestibility of these cited fractions and the metabolizability of the CE. The weight gain, as well as the feed/gain conversion for DM, digestible DM, CP, CE, DE and ME were evaluated. The development of the digestive tract was also evaluated. The milk replacer intakes were similar for all treatments. The DM, digestible DM, CP, DP, CE, DE and ME intake reduced with the increase of fNDF and total NDF levels in diets. These reductions were more severe in younger development phases. In the finishing phase the effect of the increase of fNDF in the diets over the nutrient intake was less important, affecting only the intake of digestible DM, DE and ME. The NDF and ADF intake increased proportionally to the increase of fNDF levels in the diets, as well as the digestible NDF and digestible ADF intake in the older phases. However in the younger phases the higher intake of digestible NDF and digestible ADF were observed for the diets containing intermediate levels of fNDF. In younger phases (suckling and post weaning phases), the higher digestibility of DM, NDF and ADF were reached with intermediate levels of fNDF in the diets, but in older phases (growing and finishing phases) there was no effect of the levels of fNDF in the diets on these fractions. The digestibility of CP and CE fractions, the metabolizability of CE and the crude protein conversion was not affected by the levels of FDNf in the diets in any of the development phases. The crude energy conversion presented a quadratic behavior, with better results for the intermediate levels of FDNf in the diets, but only in the post weaning phase. The conversions of DM, digestible DM, CP, CE, DE and ME were not affected by the levels of FDNf in the diets in any of the development phases. Considering each diet separately, the feed (and nutritional fractions of the feed) conversions decreased as the animals got older. For diet A, this decreasing behavior was drastic. In younger phases (suckling and post weaning phases) diet A provided better conversions but in the latter phases (growing and finishing phases) it provided the worse conversions. Only in the post weaning phase the weight gain presented a significant decrease with the increase of the fNDF levels in the diets. In the suckling phase this decrease was minimum, because the solid diet had little importance when compared to the liquid diet. In phase 3 (83 to 123 days) this decrease was less severe as the animals had already recovered from the stress of weaning and they presented larger capacities of ruminal degradation of food. In the last phase (123 to 173 days) the fNDF levels in the diets did not affect the daily weight gain, because the animals already presented a fully developed rumen, with a clear need for a minimum of fiber in the diet, specially for effective fiber. These observations allow us to conclude that the level of fNDF in the diets should increase as the animals grow older. The levels of fNDF influenced the development of the stomach compartments, increasing their development with the increase of fNDF levels in the diets, and it was more pronounced in the most advanced ages. Considering the influence of the age of the animal on the organ development, the animals fed with diet A presented a smaller development of the rumen and abomasum and a slower development of the omasum. The intestines presented larger development with the increase of fNDF levels in the diets. This became evident at the age of 173 days for the small intestine and at the age of 83 days for the large intestine. The development of the liver was not influenced by the diets. Finally, it can be said that diets with smaller levels of fNDF allowed larger intakes, but those larger intakes did not necessarily led to better conversions rates and weight gain. Thus the conclusion is that until the post weaning phase, diets with smaller fNDF levels would be more efficient. Also the fNDF level in the diets should be increased after this phase to obtain a more efficient conversion and weight gain. A gradual increase of the fNDF levels in the diets as the animals grow older would be the most advisable way of feeding lambs in order to obtain better results. These results suggest that the optimum FDNf level in the diet probably is between the ones in diets B and C. Nonetheless further studies are necessary to determine the levels with better accuracy.

ASSUNTO(S)

metabolizabilidade rumen consumo effective fiber nutricao e alimentacao animal feed conversion conversÃo alimentar ÃrgÃo digestivo digestive tract rumen digestibility digestibilidade consumption fibra efetiva metabolizabilizable

ACESSO AO ARTIGO

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