Mitochondrial abundance and function in muscle from beef steers with divergent residual feed intakes

摘要

The aim of this study was to evaluate the relationship between muscle mitochondrial function and residual feed intake (RFI) in growing beef cattle. A 56-day feeding trial was conducted with 81, individually fed, Angus x Hereford steers. Animals were weighed eveiy 14 d and feed intakes were monitored daily. High and low RFI animals were defined as >0.5 standard deviations above and below zero, respectively, with animals in between being medium RFI. Low RFI steers consumed less DM and had a greater G:Fratio than the high RFI group (P<0.05). The most extreme individuals from the low and high RFI groups were selected to assess mitochondrial function (n=5 low RFI and n=6 high RFI). State 3 and State 4 respiration rates were similar between groups. Respiratory control ratios (RCR, i.e. State 3 : State 4 oxygen uptakes) declined with age, and were greater in low RFI steers as compared to high RFI steers when adjusted for age by analysis of covariance (7ML018). Mitochondrial complex II activity levels pergram of muscle is an indicator of mitochondrial content and were greater in low RFI steers than in high RFI steers (P=0.04). These data suggest that skeletal muscle mitochondria are more abundant and show greater coupling between respiration and phosphorylation in low RFI than in high RFI steers.