Nutritive value of elephant grass silage added with cottonseed cake in diet for sheep

ABSTRACT The objective was to evaluate the intake, nutrient digestibility and nitrogen balance in sheep fed diets containing elephant grass (Pennisetum purpureum Schum) silage containing 0; 7; 14 and 21% cottonseed cake. Twenty Morada Nova sheep were used in a completely randomized design with four treatments and five replicates. The diets were isoproteic, isoenergetic and isofibrous. There was no effect of cottonseed cake levels on nutrient intake and digestibility coefficient of ether extract. The digestibility coefficients of dry matter, organic matter, crude protein, total carbohydrates and non-fiber carbohydrates presented a linear reduction with the levels of cottonseed cake varying from, respectively, 537.97 to 421.21; 566.54 to 446.42; 595, 38 to 415.62; 544.90 to 421.84 and 697.85 to 521.03, at levels 0 and 21%. The N intake and the urinary N, in the various forms, as well as the fecal N expressed in g day-1 and g kg-0.75, were not influenced by the cottonseed cake levels in the silages. The fecal N presented a quadratic response with a minimum value of 39.09% NI when 3.20% cottonseed cake was added to elephant grass silage. Nitrogen balance showed a quadratic response with a maximum value of 6.50 g day-1; 0.79 g kg-0.75 and 35.07% NI at the levels of 3.25, 5.00 and 4.95% cottonseed cake, respectively. The inclusion of 5% cottonseed cake in elephant grass silage promotes better efficiency in the use of protein sources when aimed at using silage in the composition of a balanced diet.

摘要：本研究旨在评估饲喂添加0、7、14和21%棉籽饼的象草（Pennisetum purpureum Schum）青贮饲料的绵羊的采食量、养分消化率及氮平衡。试验选用20只莫拉达诺瓦绵羊，采用完全随机试验设计，设置4个处理组与5个重复。各试验日粮等蛋白、等能、等纤维。棉籽饼添加水平对乙醚提取物（ether extract）的养分采食量及消化系数无显著影响。随着棉籽饼添加水平从0%提升至21%，干物质（dry matter）、有机物（organic matter）、粗蛋白质（crude protein）、总碳水化合物（total carbohydrates）及非纤维碳水化合物（non-fiber carbohydrates）的消化系数分别呈线性下降，对应数值区间依次为537.97~421.21、566.54~446.42、595.38~415.62、544.90~421.84及697.85~521.03。不同形态的氮采食量、尿氮，以及以g·d^-1和g·kg^-0.75表示的粪氮，均不受青贮饲料中棉籽饼添加水平的影响。粪氮占氮摄入量（NI）的比例呈二次响应，当象草青贮中添加3.20%棉籽饼时，该比例达到最低值39.09%。氮平衡呈二次响应，当棉籽饼添加水平分别为3.25%、5.00%和4.95%时，氮平衡分别达到最大值6.50 g·d^-1、0.79 g·kg^-0.75及35.07% NI。在象草青贮饲料中添加5%棉籽饼，若以青贮饲料作为平衡日粮的组成部分，可有效提升蛋白质源的利用效率。