Compensatory growth of carcass tissues and visceral organs in beef heifers

Twenty-eight beef heifers (222 +/- 22 kg SD; 226 +/- 10 d SD on day 0) from a composite breed were used to investigate weight recovery of muscle, bone, fat, and visceral organs, and the contribution of gut fill to compensatory growth. Two heifers were slaughtered on day 1. Of the remaining 26 heifers, 12 were fed ad libitum (ADLIB) and 14 were given a maintenance ration for 92 d, followed by realimentation (REST). They were randomly assigned in pairs to slaughter dates and slaughtered over a wide range of live weights (200 to 460 kg). The allometric equation, Y = aX(b), was used to study the recovery patterns of carcass tissues and visceral organs. Average daily gains were higher (P = 0.001) in REST than in ADLIB heifers during realimentation. Feed restriction affected some carcass tissues and visceral organs, but realimentation reversed this, and there were no differences in body composition between treatments by about 460 kg live weight. Treatment did not affect the allometric growth coefficients (b values) for muscle and bone relative to side weight, but the b value for total fat relative to side weight was greater (P = 0.03) in REST than in ADLIB heifers. Relative to total fat, the b values for subcutaneous and intermuscular fat were greater (P = 0.01) and smaller (P = 0.03), respectively, in REST than in ADLIB heifers. The liver, empty stomach, spleen, and pancreas showed rapid recovery during realimentation of REST heifers. Gut fill did not contribute to compensatory weight gain.