Effect of compensatory growth on mammary growth and development in beef heifers

Abstract

Twenty-eight beef heifers (222 ± 22 kg SD; 226 ± 10 days SD on day 0) from a composite breed were used to study the effect of feed restriction followed by realimentation on mammogenesis. Two heifers were slaughtered on day 1, and of the remaining 26 heifers, 12 were fed ad libitum (ADLIB) and 14 were restrict-fed followed by realimentation (REST) on day 92. The heifers were randomly assigned in pairs to slaughter dates over a wide range of live weights (200 to 465 kg). Mammary parenchymal tissue was assayed for DNA, RNA, protein, and lipid concentrations. The mammary glands from REST heifers were lighter ( P < 0.05) than those from ADLIB heifers except at the final live weight, although there was still a tendency for lighter ( P = 0.07) mammary glands in the former than in the latter heifers. There were significant overall time ( P = 0.02) and treatment ( P = 0.09) effects on DNA concentration; there was a tendency toward greater parenchymal DNA concentration values in REST than in ADLIB mammary glands during the realimentation period. There were no significant treatment effects ( P > 0.05) on parenchymal RNA or protein concentrations. There was a time effect ( P = 0.02) on parenchymal lipid concentration, and there was less lipid in the mammary parenchyma of REST than ADLIB glands although the difference was only significant ( P = 0.02) on one slaughter date. These results suggest that feed restriction followed by realimentation may lead to enhanced mammary development in beef heifers.