Feed efficiency and meat quality of crossbred beef heifers classified according to residual feed intake

AbstractThis study aimed to evaluate feed efficiency and meat quality of 31 three-crossbred beef heifers during 84 days in a feedlot system. A 60:40 concentrate and sorghum silage ration on DM basis (ME = 2.73Mcal/kg of DM, CP = 11.90% DM) was fed ad libitum. Based on residual feed intake (RFI) calculations, the heifers were ranked in three groups of feed efficiency: High RFI (average mean = 0.776; n = 9), medium RFI (average mean = -0.010; n = 11), and low RFI (average mean = - 0.624; n = 11). High RFI heifers consumed 4.56% more DM per day than low RFI heifers (P <0.05). The ADG did not differ (P> 0.05) among RFI groups (1.40kg/day). No differences (P>0.05) were detected for digestibility of the nutrients: DM (64.00%), CP (60.01%), crude fat (72.90%), NDF (54.80%) and non-fibrous carbohydrate (NFC) (78.91%). There were no differences between low and high RFI groups for slaughter weight (475.00 vs. 479.55kg), hot carcass weight (259.09 vs. 261.44kg), Longissimus dorsi (LD) area (69.02 vs. 68.11 cm2), back-fat thickness (5.74 vs. 6.26 cm), shear force (5.45 vs. 5.19kg), sensorial traits of LD muscle, LD color (intensities L=40.47 a*=24.74 and b*=16.13) or commercial cuts yield. Low RFI heifers presented similar meat quality and carcass traits as high RFI heifers, however low RFI heifers consumed less DM (kg/d).

摘要
本研究旨在评估31头三元杂交肉牛后备母牛在育肥系统中饲养84天的饲料利用率与肉品质。试验采用以干物质（DM）为基准的60:40精料与高粱青贮日粮（代谢能=2.73兆卡/千克干物质，粗蛋白=11.90%干物质），以自由采食方式饲喂。基于剩余采食量（RFI）的计算结果，将受试后备母牛按饲料利用率分为三组：高剩余采食量组（平均均值=0.776，n=9）、中剩余采食量组（平均均值=-0.010，n=11）与低剩余采食量组（平均均值=-0.624，n=11）。高剩余采食量组母牛的每日干物质采食量较低剩余采食量组高4.56%（P<0.05）。各组间平均日增重（ADG）无显著差异（P>0.05），均值均为1.40kg/天。各营养物质的消化率均无组间显著差异（P>0.05）：干物质（64.00%）、粗蛋白（60.01%）、粗脂肪（72.90%）、中性洗涤纤维（NDF）（54.80%）与非纤维性碳水化合物（NFC）（78.91%）。低、高剩余采食量组在屠宰体重（475.00 vs 479.55kg）、热胴体重（259.09 vs 261.44kg）、背最长肌（LD）面积（69.02 vs 68.11 cm²）、背膘厚度（5.74 vs 6.26 cm）、剪切力（5.45 vs 5.19kg）、背最长肌感官性状、背最长肌颜色（亮度L=40.47、a*=24.74、b*=16.13）以及商业分割肉出品率方面均无显著差异。低剩余采食量组母牛与高剩余采食量组的肉品质及胴体性状无显著差异，但低剩余采食量组的每日干物质采食量更低（kg/d）。