Forage cactus associated with different fiber sources for lactating Sindhi cows: intake, digestibility and microbial protein production

This experiment was carried to evaluate the effect of forage cactus with different fiber sources (elephant grass hay [EGH], corn straw [CS], hay of cassava shoots [HCS], fresh sugarcane bagasse [FSB], and hydrolyzed sugarcane bagasse [HSB]) on intake, apparent digestibility and macrobiotic protein production of cows. Five cows with 265 kg average body weight, 4.95 kg average daily milk yield and 5.22 kg 4% fat-corrected milk yield were randomly allocated to a 5 × 5 Latin square design. The animals fed cactus associated with CS, EGH and HCS showed higher intake of DM and nutrients. However, regarding the digestibility, diets with sugarcane bagasse showed higher digestibility compared with those with CS and hay. For microbial protein, the excretion of purine derivatives, synthesis of microbial N and microbial protein production were higher in the treatment with CS than in the treatment with sugarcane bagasse. On the other hand, the treatment with EGH and HCS did not have statistical differences compared with the other cases. The mean efficiency of microbial protein synthesis of the experiment was 131 g microbial crude protein/kg of TDN. The treatment with CS showed better efficiency; however, it was statistically superior only compared with FSB. The other treatments did not show statistical difference compared with the other cases. Diets with cactus associated with corn straw, hay of elephant grass or hay of cassava shoots provide higher intake of dry matter and nutrients and better metabolic response compared with diets with cactus associated with sugarcane bagasse for lactating Sindhi cows.本试验旨在评估不同纤维来源的饲用仙人掌（辅以象草干草（elephant grass hay, EGH）、玉米秸秆（corn straw, CS）、木薯嫩枝干草（hay of cassava shoots, HCS）、新鲜甘蔗渣（fresh sugarcane bagasse, FSB）及水解甘蔗渣（hydrolyzed sugarcane bagasse, HSB））对奶牛干物质（dry matter, DM）摄入、表观消化率及微生物蛋白产量的影响。选取5头平均体重265kg、平均日产奶量4.95kg、4%脂肪校正奶（4% fat-corrected milk）产量为5.22kg的试验牛，采用5×5拉丁方试验设计进行随机分组。饲喂联合仙人掌与CS、EGH及HCS日粮的试验牛，其干物质与营养物质摄入量更高。然而在表观消化率方面，添加甘蔗渣的日粮组消化率显著高于添加CS与干草的日粮组。针对微生物蛋白指标，CS组的嘌呤衍生物（purine derivatives）排泄量、微生物氮（microbial N）合成量及微生物蛋白产量均显著高于甘蔗渣组。相较而言，EGH组与HCS组与其余各组均无统计学差异。本试验的微生物蛋白合成平均效率为131g微生物粗蛋白/kg总可消化营养物（total digestible nutrients, TDN）。CS组的合成效率最优，但仅显著高于FSB组；其余各组间均无统计学差异。对于辛地（Sindhi）泌乳牛而言，联合仙人掌与玉米秸秆、象草干草或木薯嫩枝干草的日粮，相较于联合仙人掌与甘蔗渣的日粮，可提升干物质与营养物质摄入量，并获得更优的代谢响应。