Ruminal fermentation of Nellore steers fed crude glycerine replacing starch vs. fibre-based energy ingredient in low or high concentrate diets

ABSTRACT. Twelve ruminally cannulated steers (401.0 ± 41.5 kg) and 24 mo were used in a replicated arrangement truncated Latin Square with six animals in six treatments and four periods to evaluate the effect of crude glycerine (CG; 80.3% of glycerol) with starch or fiber-based energy ingredients in the concentrate on DMI, DM (DMD) and NDF digestibility (NDFD) and ruminal parameters. Experimental periods were 19 days (14 days for adaptation and 5 days to sampling). Diets were: CO - without CG and corn as ingredient of concentrate; CGC - inclusion of CG (10% of DM) with corn in the concentrate; and CGSH - inclusion of CG (10% of DM) with soybean hulls (SH) in the concentrate. All three diets were offered at low (LC) or high (HC) concentrate level, CL (40 or 60%). Animals fed LC or HC diets had similar DMI, DMD and NDFD. Animals fed diets with CG associated with corn or SH had higher propionate concentrations and lower A:P ratio. Diets with HC increase the propionate but do not affect the NDFD. CG (10% of DM) can be used to replace corn or SH in diets with 40 or 60% of concentrate, without affect NDFD.摘要：本试验采用重复排列的不完全拉丁方试验设计，选取12头体重为401.0±41.5 kg、24月龄的瘤胃插管肉牛，设置6个处理组与4个试验周期，旨在探究精饲料中添加粗甘油（crude glycerine, CG，甘油含量80.3%）搭配淀粉基或纤维基能量原料对干物质采食量（dry matter intake, DMI）、干物质消化率（dry matter digestibility, DMD）、中性洗涤纤维消化率（neutral detergent fiber digestibility, NDFD）及瘤胃参数的影响。试验周期共计19天，其中14天为适应期，5天为采样期。试验日粮分为三类：CO组：不含CG，精饲料以玉米为原料；CGC组：精饲料中添加占干物质10%的CG，且以玉米为原料；CGSH组：精饲料中添加占干物质10%的CG，且以大豆皮（soybean hulls, SH）为原料。上述三类日粮均设置两个精料水平：低精料组（LC，精料占比40%）与高精料组（HC，精料占比60%），即精料水平（concentrate level, CL）为40%或60%。饲喂LC或HC日粮的肉牛，其DMI、DMD与NDFD无显著差异。饲喂添加CG搭配玉米或大豆皮日粮的肉牛，瘤胃丙酸浓度更高，乙酸与丙酸比值（A:P ratio）更低。高精料水平日粮可提升瘤胃丙酸浓度，但对NDFD无影响。在精料占比为40%或60%的日粮中，可使用占干物质10%的CG替代玉米或大豆皮，且不会影响NDFD。