Beef Species Symposium I: Cattle Adapted to Tropical/Subtropical Environments
Cattle raised in tropical/subtropical environments typically are Bos indicus full blood or crossbred cattle. While they are ideally suited for reproductive performance in hot and humid climates, they frequently produce carcasses with lesser marbling scores than Bos taurus cattle. Early research from our laboratory compared subcutaneous (s.c.) and intramuscular (i.m.) adiposity and lipogenic capacity in Angus and Santa Gertrudis and Angus and Braford steers.; cattle with predominantly Bos indicus has lower marbling scores and smaller i.m. adipocytes. These and other studies suggested that genetic differences in adipose tissue metabolism between B. taurus and B. indicus breed types were expressed only when there were visible differences in marbling score and adjusted fat thickness (AFT). A subsequent study suggested that fatty acid Δ9 desaturase enzyme activity (stearoyl-CoA desaturase [SCD]) was greater in adipose tissue from Bos indicus cattle than in Bos taurus cattle, thereby resulting in a greater proportion of oleic acid (18:1n-9). We recently reported a comprehensive study comparing three-fourths Brahman progeny to three-fourths Angus progeny, in which progeny were raised to a constant age and constant AFT. Subcutaneous adipocyte cell was similar between Brahman and Angus progeny (276 vs 288 pL) but i.m. adipocytes were smaller in Brahman progeny than in Angus progeny (170 vs 207 pL). This was consistent with the lower marbling scores of the Brahman progeny. There was no difference between the proportions of stearic acid (18:0) and oleic acid between Brahman and Angus progeny; nor was there a difference in s.c. or i.m. adipose tissue SCD activity. We conclude that time on feed and/or animal age has a greater impact on fatty acid than genetics (Brahman vs Angus). However, research has demonstrated consistently that i.m adipose tissue in Bos indicus cattle does not develop to the same extent as in Bos taurus cattle.