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

Abstract

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 (P<0.05) according to the increase in the level of sunflower meal insertion in the diets. The milk yield (26.37 kg/day) and the contents and quantities in milk protein, lactose, total solids (TS), nonfat dry extract (ESD) and urea nitrogen (MUN) and feed efficiency (EA) were not altered (P>0.05) in function of the diets. Milk yield corrected for 4% fat and milk fat content and amount were linearly influenced (P <0.05) by the diets used. Levels of soybean meal replacement by sunflower meal in the diets did not influence (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) by collection times, presenting higher blood concentrations 4 hours after the beginning of feeding. Sunflower meal may be the main protein source, substituting up to 100% soybean meal in lactating cows.