Consumo, digestibilidade aparente dos nutrientes e desempenho de vacas leiteiras sob pastejo em função de níveis de concentrado e proteína bruta na dieta

• Autor(a) principal: Silva, Cristiano Viana da
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5848
• topic: Concentrado; Pasto; Desempenho; Leite; Bovino de leite; Concentrate; Pasture; Performance; Dairy cattle; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL::AVALIACAO DE ALIMENTOS PARA ANIMAIS

This work was developed with the objective of evaluating the effects of concentrate and crude protein (CP) levels on the intake and apparent digestibility of nutrients, and milk production and composition. Eight crossbred Holstein-Zebu cows with 520±40 kg were distributed in an 8 x 8 Latin square (LS) in eight periods of 10 days, for evaluation of four levels of concentrate ration (0, 1, 3 and 5 kg/cow/day) and two levels of crude protein (9 and 12% of CP in the total dietary dry matter). The experiment was conducted in pasture of elephant-grass (Pennisetum purpureum, Schum) in the rainy season and the concentrates were constituted of corn meal, soybean meal, urea and mineral mixture. The experiment was analyzed in LS including effects of treatment, animal and period. In the 10th day of the experimental period, it was collected a sample of milk per animal in each of the two daily milking times, for later mixture in a composite sample. In the 9th and 10th days, at 8:00 and 16:00 hours, respectively, samples of feces were collected, and the indigestible acid detergent fiber (ADFi) was utilized as internal indicator for the estimates of fecal dry matter excretion. The dry matter intake (DMI) did not differ among the diets, both for concentrate and crude protein (P>0.05), in which the pasture intake tended to decrease with the increase of concentrate, not differing in relation to levels of crude protein (CP). The CP intake was increased by the increase in levels of supplementation and crude protein in the diet, while the intakes of total digestible nutrients (TDNI), non-fiber carbohydrates (NFCI), neutral detergent fiber (NDFI) and ether extract (EEI) increased with the increasing levels of concentrate, with no difference in relation to levels of crude protein. The intake of non-fiber carbohydrates (NFCI) increased with the increasing levels of concentrate and crude protein. The coefficient of digestibility (CD) of DM and NFC increased and decreased (P<0.05), respectively, by the increase in concentrate level, not differing with the levels of crude protein; the CD of CP increased with the increase in concentrate and crude protein levels (P<0.05), but the effect for CD of NDF only happened when the level of CP increased in the diet. The milk production (MP) increased with the increasing levels of concentrate (P<0.05), with no influence (P>0.05) of protein levels, being explained by the following equation: &#375; = 11.9 + 0.322*C. The content of fat, protein, lactose and dry extract of milk were not influenced by the levels of concentrate, but when increased the level of CP in the diet there was increase in the content of lactose and dry extract of milk. Cows with mean production of 12 kg of milk/day can be fed with diets containing 9% of CP, because there was no effect of CP levels in the diet in the range of 9 to 12% in the animal's performance. In spite of the response in milk production by supplementation be linear, after 3 kg/cow/day, there was a trend for diminishing increase following the curvilinear model of Michaelis-Menten, typical of enzyme systems. The milk production increased with the increase in the level of supplementation (0.32 kg/kg of concentrate), but did not change with increasing levels of crude protein in the diet, different from NRC 2001 of dairy cows that consider a linear response of 2.2 kg of milk/kg of concentrate ration.