|Caldwell, L - TEXAS AGRILIFE RESEARCH|
|Welch, JR., T - TEXAS AGRILIFE RESEARCH|
|Randel, R - TEXAS AGRILIFE RESEARCH|
Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: January 2, 2009
Publication Date: February 3, 2009
Citation: Caldwell, L.C., Chase, C.C., Riley, D.G., Coleman, S.W., Phillips, W.A., Welch, Jr., T.H., Randel, R.D. 2009. [abstract]Influence of tropical adaptation on plasma insulin-like growth factor-I and residual feed intake in purebred and crossbred beef cattle. American Society of Animal Science Southern Section Meeting, January 31, 2009 to February 3, 2009, Atlanta, Georgia. Technical Abstract: The objective of this study was to determine if plasma concentrations of insulin-like growth factor-I (IGF-I) differed among heifers and steers produced from three-breed diallel matings using temperate and tropically adapted breeds of cattle in Brooksville, FL. Additionally, for steers only, body weight and feed intake data were collected during individual finishing phase feeding trials, at El Reno, OK. The data were used to calculate residual feed intake (RFI) and then compared to concentrations of IGF-I to test whether IGF-I could be used as a predictor of RFI. The breeds consisted of temperate Bos taurus (A; Angus), tropical Bos indicus (B; Brahman), and tropical Bos taurus (R; Romosinuano). Purebreds (AA, BB, RR) and crossbreds (ABX, ARX, BRX) from the 2003 and 2004 calf crops were evaluated. Blood samples were obtained from 10 heifers and 10 steers of each breed-type. Steer samples were taken at weaning and d0 and 60 of the finishing phase. Heifer samples were taken at weaning and d0 and 84 of each trial. Concentrations of IGF-I were determined by RIA. Breed differences in concentration of IGF-I among heifers and steers were observed (P < 0.05), with AA exhibiting the lowest values. Correlations between concentrations of IGF-I and RFI, pooled over all steer breeds, were weak for all sample dates, with r values ranging from -0.136 to 0.066 (P > 0.05). Results suggest that RFI is unrelated to plasma concentration of IGF-I in these breed-types; however, relative to the temperate Bos taurus breed, plasma concentrations of IGF-I were greater in male and female tropically-adapted breed-types.