Effects of nutrition and age on adipose tissue growth and development in lambs
Authors:   , Haugebak Clayton D. 
Published: June 2024

Forty wether lambs weighing approximately 27 kg each were randomly divided into two equal groups. One group was fed at the maintenance level, the other group fed ad libitum during a 150 day growing phase. At the end of the growth phase four lambs from each group were slaughtered to assess initial carcass characteristics and composition, adipocyte size and number, lipoprotein lipase activity and fatty acid composition. The remaining 16 lambs in each group were then randomly divided into two further groups with eight lambs from each group fed ad libitum a finishing diet containing 9 percent protein and the other eight lambs from each group fed ad libitum a finishing diet containing 12 percent protein. Four lambs from each treatment group (maintenance-low protein; maintenance-high protein; ad libitum-low protein and ad libitum-high protein) were slaughtered after 82 days on the ad libitum finishing diets. The remaining 16 lambs were slaughtered after a total of 132 days on the finishing diets. Lambs fed ad libitum and slaughtered at the end of the growth phase produced carcasses with less percent bone and muscle but greater percent adipose tissue than carcasses from lambs fed at maintenance and slaughtered at the end of the growth phase. During the finishing phase, percent bone and muscle decreased and percent adipose tissue increased in the carcasses for lambs of both nutritional regimens of the growth phase. Dietary protein treatment during the finishing phase did not affect (P>.05) carcass composition. The most significant increase in percent adipose tissue occurred for lambs fed at maintenance during the growth phase, and subsequently fed finishing diets ail libitum, between the end of the growth phase and slaughter date I of the finishing phase. Lambs fed ad libitum and at maintenance during the growth phase increased in adipose tissue by adipocyte hypertrophy during the finishing phase. Hypertrophy occurred in subcutaneous and perirenal adipocytes, but not in intermuscular adipocytes. Although the lambs fed ad libitum during the growth phase contained larger adipocytes, the percent increase in adipocyte volume at each slaughter date during the finishing phase relative to the adipocyte volume of lambs slaughtered at the end of the growth phase (for each group) was greater for lambs fed at maintenance during the growth phase. Adipocyte hyperplasia during finishing occurred in lambs fed at maintenance during the growth phase. Hyperplasia for the lambs fed at maintenance occurred in subcutaneous and intermuscular adipose tissue. There was no hyperplasia in perirenal adipose tissue. Lipoprotein lipase activity was negligible in the adipose tissues from lambs fed at maintenance and slaughtered at the end of the growth phase. This result was attributed to the low nutritional state of these lambs at the time of slaughter. However, once the lambs fed at maintenance were subsequently given finishing diets ad libitum, the increase in carcass adipose tissue was paralleled by an increase in total lipoprotein lipase activity. The increase in activity was due primarily to increased lipoprotein lipase activity in the subcutaneous adipose tissue. Total lipoprotein lipase activity increased in the early stage of the finishing period for those lambs fed ad libitum during the growth phase. This increase in total activity also was due to increased lipoprotein lipase activity in subcutaneous adipose tissue. The lipoprotein lipase activity of the carcass extramuscular adipose tissues was positively related to intramuscular fat deposition. Analysis of fatty acid composition indicated that as lambs increased in age, the subcutaneous and intermuscular adipose tissue fat became less saturated. Intramuscular fat was more unsaturated than fat from extramuscular adipose tissues.