Growth performance and meat quality of feedlot steers fed diets with or without natural feed additive

ABSTRACT The objective of this study was to evaluate the growth performance and meat quality of feedlot Aberdeen Angus steers fed high-concentrate diets with or without a natural feed additive composed of a mixture of yeasts and essential oils (EO). A completely randomized design with two diets (with or without natural feed additive) and 12 replicates was used. Twenty-four steers with initial shrunk body weight of 402.62±48.2 kg and average age of 18±2.0 months were used. Steers were fed ad libitum a diet containing 777.3 g of concentrate/kg dry matter (DM) and 222.7 g of corn silage/kg DM for 74 days. The mixture of yeast and EO was supplied at the rate of 10.0 and 0.117 g/animal/day, respectively. Average daily weight gain and feed efficiency in the adaptation period was greater in animals fed natural feed additive; however, there was no difference for the total experimental period. Dry matter intake, carcass weight, carcass yield, proportion of carcass bone, carcass muscle + fat:bone ratio, round thickness, and arm length were not altered by treatments. The inclusion of a natural feed additive in the diet increased the cooling loss (0.98 vs. 1.25%), proportion of carcass muscle (51.32 vs. 54.56%), carcass muscle:fat ratio (1.70 vs. 2.11%), leg length (68.79 vs. 70.71 cm), and arm perimeter (36.70 vs. 37.88 cm) and reduced the proportion of carcass fat (30.17 vs. 25.92%). Carcass length was greater in animals fed the diet with a natural feed additive. Meat color, texture, and marbling were not altered by treatments. The addition of natural feed additive to high concentrate diets does not alter the productive performance of feedlot Aberdeen Angus steers, although it can increase the proportion of lean meat of carcasses.

摘要：本研究旨在评估饲喂高精料日粮（high-concentrate diets）的育肥场安格斯阉牛的生长性能与肉品品质，日粮分别添加或不添加由酵母与精油（essential oils，EO）复配而成的天然饲料添加剂（natural feed additive）。本研究采用完全随机试验设计（completely randomized design），设置两种日粮（添加与不添加天然饲料添加剂），共12个重复组（replicates）。试验选用24头初始空腹体重（shrunk body weight）为402.62±48.2 kg、平均月龄为18±2.0个月的安格斯阉牛，自由采食（ad libitum）干物质（dry matter，DM）基础下含777.3 g/kg精料与222.7 g/kg玉米青贮（corn silage）的日粮，试验周期为74天。酵母与精油复配物的添加剂量分别为10.0 g/头·天与0.117 g/头·天。适应期内，添加天然饲料添加剂组的试验牛平均日增重（average daily weight gain）与饲料转化效率（feed efficiency）更高，但整个试验周期内两组无显著差异。干物质采食量（dry matter intake）、胴体重（carcass weight）、胴体出肉率（carcass yield）、胴体骨比例（proportion of carcass bone）、胴体肌肉与脂肪-骨比值（carcass muscle + fat:bone ratio）、后腿厚度（round thickness）及臂长（arm length）均不受试验处理的影响。日粮中添加天然饲料添加剂可提升冷却损耗（cooling loss）（0.98% vs 1.25%）、胴体肌肉比例（proportion of carcass muscle）（51.32% vs 54.56%）、胴体肌肉-脂肪比值（carcass muscle:fat ratio）（1.70 vs 2.11）、腿长（68.79 cm vs 70.71 cm）及臂围（arm perimeter）（36.70 cm vs 37.88 cm），同时降低胴体脂肪比例（proportion of carcass fat）（30.17% vs 25.92%）；添加组试验牛的胴体长度更长。肉色、质地及大理石纹（marbling）均不受试验处理的影响。综上，在高精料日粮中添加天然饲料添加剂虽不会改变育肥安格斯阉牛的生产性能（productive performance），但可提升其胴体瘦肉比例。