Valor nutritivo da silagem do resíduo úmido de cervejaria na alimentação de vacas leiteiras

Abstract

The aim of this study was to evaluate the inclusion of wheat bran, soybean hulls or ground corn in the ensilage of wet brewer's grain, and its effects on the fermentation dynamics, nutritional value of silages, as well as the production, efficiency and composition of milk of Holstein cows. First, the wet brewers grain (WBG) was ensiled in experimental silos, in natura (SWBG), or adding additives with high dry matter content (absorbent): 20% wheat bran (SWB), 20% soybean hulls (SSH) or 20% ground corn (SGC), in natural matter basis. The experimental design was a randomized 4x7 factorial, with four silages and seven times of evaluation, being zero time evaluated in the ensilage, and others (1, 3, 7, 14, 28 and 56 days) in the opening of the silo, and four replications. With respect to bromatological characterization, the inclusion of additives linearly increased the dry matter (DM) and decreased the crude protein (CP) contends. Concerning the dynamic fermentation, the addition of ground corn to the WBG provided less buffer capacity. The ammonia nitrogen was higher for SWB after 56 days of ensiling and lower for SWBG at time 0. The population of fungi was higher in SGC and SWB. The SWBG and SGC showed the highest results of lactic acid bacteria and clostridia in silage in the opening at 56 days. The use of absorbent additives increases the available carbohydrates and proteins fractions of ensiled wet brewers grain, and the use of ground corn was beneficial, because it reduces effluent and dry matter losses, and improves in vitro digestibility of dry matter. The opening of the silos is indicated at 28 days, due the lower population of clostridia in silage. With these results, to determine the nutritive value of silages additives, there were used four Holstein cows, multiparous, distributed in Latin square design (4x4) with four experimental periods of 21 days each and four treatments. The diets were composed of Tifton 85 hay, WBG silages (SWBG, SWB, SSH or SGC) and concentrate, 60:40 forage to concentrate ratio. The DM and organic matter (OM) intake increased with the SWB and SGC diets. The higher digestibility of DM, organic matter, neutral detergent fiber (NDF) and CP were observed in SSH and SGC diets. Daily production, corrected to 3.5 % fat, and milk composition were not changed by diets. The concentrations of urea nitrogen in milk were higher for SGC diet. The inclusion of soybean hulls or ground corn in the silage of WBG increases the dry matter and nutrients digestibility however, the use of absorbent additives does not change the production, efficiency and milk composition of Holstein cows. Posteriorly, in order to evaluate levels of inclusion of the WBG silage on production parameters, there were used five primiparous Holstein cows, distributed in Latin square design (5x5) with five experimental periods of 21 days each and five . treatments. Diets were composed of corn silage and SWBG, concentrated feed, in 60:40 forage to concentrate ratio. Treatments consisted of control diet without adding SWBG, and the others with 15 %, 20 %, 25 % and 30 % inclusion of SWBG. The dry matter intake was not affected by the inclusion of SWBG, and dry matter digestibility decreased linearly. The ruminal ammonia showed a negative linear effect, and the concentrations of acetate and propionate, milk production and efficiency showed a quadratic effect with the inclusion of SWBG. The inclusion of wet brewer's grain silage, in the diet of lactating cows decreased the dry matter and nutrients digestibility . However, it is favorable to increase the milk production and efficiency. The fat content in milk decreases linearly, but increases the unsaturated fatty acids and conjugated linoleic acid.