Melo et al., 2003. Rev. Bras. Zootec., 32 (3): 727-736
Substituição parcial do farelo de soja por uréia e palma forrageira (Opuntia fícus indica Mill) em dietas para vacas em lactação: I. Desempenho.
The work was carried out to evaluate the partial replacement of soyabean meal by urea and forage cactus on the performance of lactating Holstein-Friesian cattle. Eight cows with 90 days in milk and 600 kg of initial average LW were assigned in a two 4*4 Latin square design. The urea represented 0.0, 0.8, 1.54 and 2.40% of dry matter (DM) of the diets, corresponding to 2.32, 4.65, 6.66 and 8.02% of crude protein (CP) levels in the form of nonprotein nitrogen compounds (NPN), that represented the experimental treatments. It was shown that there was a quadratic effect of levels of NPN on the intake of CP, with maximum intake of 3.3 kg/day with 4.71% of NPN. The calcium (Ca) intake increased and dry matter (DM), organic matter (OM), ether extract (EE), total carbohydrates (TCH), nonfibre carbohydrates (NFC), acid detergent fibre (ADF) and total digestible nutrients (TDN) intakes decreased linearly. The intakes of neutral detergent fibre (NDF) and phosphorus (P) were not affected by NPN levels. Milk production and fat corrected milk (3.5%) decreased linearly as levels of urea and forage cactus increased. The yield of fat, protein, milk composition and feed efficiency ratio were not affected by NPN levels.