Farelo de girassol em substituição ao farelo de soja na dieta de vacas em lactação

The objective was to evaluate the effects of inclusion of sunflower meal replacing soybean meal in the diet of lactating cows on intake and digestibility of dry matter and nutrients, production and milk composition, feed efficiency, microbial protein synthesis, blood parameters (glucose concentration, urea and urea nitrogen) and nitrogen balance. Twelve Holstein x Gir mixed cows were used, with an initial average production of 28 ± 2.7 kg of milk / day, were distributed in a 4 x 4 triple Latin Square design, with four periods of 17 days each (ten days for adaptation of the animals to the diet and seven days for data collection and samples). The cows received diets composed of 50% corn silage and 50% concentrate (based on dry matter - MS). The diets consisted of increasing levels of sunflower meal (0%, 33%, 67% and 100%) replacing soybean meal (based on dry matter - MS). Diets did not influence (P> 0.05) the intake of dry matter (CMS), organic matter (CMO), mineral matter (CMM), crude protein (CPB) and total digestible nutrients (CNDT). The consumption of non-fibrous carbohydrates (CNFC) decreased, while consumption ether extract the (CEE) and neutral detergent fiber corrected for ash and protein (CNDFap) increased kg / day and %PV in accordance with the increase in sunflower meal level in the diets. The apparent digestibility coefficients of DM, CP, OM, NDFcp and CNF were not altered (P> 0.05) in function of the diets. However, the apparent digestibility coefficient of EE increased (P0.05) in function of the diets. Milk yield corrected for 4% fat and milk fat content and amount were linearly influenced (P 0.05) the estimated urinary volume (Ŷ = 21.52 L/day), as well as the excretion of purine derivatives, synthesis of nitrogenous compounds and the efficiency of microbial protein synthesis. The amount of nitrogen ingested and digested showed no influence of treatments (P<0.05), as well as the amount of nitrogen 15 excreted via urine, feces and milk. Nitrogen balance was not influenced by treatments (P> 0.05). The serum concentration of urea nitrogen, urea and glucose were not influenced (P> 0.05) by the treatments. However, glucose concentration was influenced (P 0,05) os consumos de matéria seca (CMS), matéria orgânica (CMO), matéria mineral (CMM), proteína bruta (CPB) e nutrientes digestíveis totais (CNDT). O consumo de carboidratos não-fibrosos (CCNF) diminuiu, enquanto que, o consumo de extrato etéreo (CEE) e fibra em detergente neutro corrigido para cinza e proteína (CFDNcp) aumentaram em kg/dia e em %PV, de acordo com o aumento no nível de farelo de girassol nas dietas. Os coeficientes de digestibilidade aparente da MS, PB, MO, FDNcp e CNF não foram alterados (P>0,05) em função das dietas. A produção de leite (26,37 kg/dia) e os teores e quantidades de proteína, lactose, sólidos totais (ST), extrato seco desengordurado (ESD) e o teor de nitrogênio uréico no leite (NUL) e a eficiência alimentar (EA), não foram alterados (P>0,05) em função das dietas. A produção de leite corrigida para 4% de gordura e o teor e a quantidade de gordura no leite foram influenciados (P0,05) a estimativa do volume urinário, assim como, as excreções dos derivados de purinas, a síntese de compostos nitrogenados e a eficiência de síntese de proteína microbiana. A quantidade de nitrogênio ingerido e digerido não apresentaram influência dos tratamentos 13 (P>0,05), assim como, a quantidade de nitrogênio excretado via urina, fezes e leite. O balanço de nitrogênio não foi influenciado pelos tratamentos (P>0,05). A concentração sérica de nitrogênio uréico, ureia e glicose não foram influenciadas (P>0,05) pelos tratamentos. Porém, a concentração de glicose foi influenciada (P