Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 10, 2011
Publication Date: July 14, 2011
Citation: Coleman, S.W., Chase, C.C., Phillips, W.A., Riley, D.G. 2011. Post-weaning feed efficiency of tropically adapted purebred and crossbred calves when fed in either winter or spring. Journal of Animal Science Supplement. 89(E Suppl. 1):273. Technical Abstract: Earlier work has shown that young, tropically adapted (Brahman and Romosinuano) cattle do not gain as rapidly as temperately adapted (Angus) cattle during the winter in OK. The objective for this study was as to compare efficiency of gains between tropically- and temperately-adapted cattle breeds. Over 3 yr, 239 purebred and crossbred steers (FI and 3-way crosses) of Angus. Brahman or Romosinuano breeding were done in Brooksville, FL, transported to EI Reno, OK in October each year, and fed in 2 phases to determine individual intake and performance. Phase I (W, ~127 d) began in November and phase 2 (S. 56 to 162 d) began in March. A grower diet (1-1% CP. 1.10 Mcal NEg/kg) was fed in W and a conventional feedlot diet (12.8% CP; 1.33 Mcal NEg/kg) in S. Body Weights were recorded at approximately 14 d intervals, ADG was determined by regressing RW on days on feed (DOF) within phase. Daily DMI was then regressed by phase on median BW and ADG to determine residual feed intake (RFI). Gain to feed (GF) was also calculated as a measure of efficiency. The statistical model incoluded fixed effects of yr, hearvest group (3 per year), age on test, and a nested term DT(ST x XB) where DT = proportion tropical breeding of dam (0, 0.5, or 1), ST = proportion tropical breeding of sire (1, or 0), and XB whether the calf was straightbred or crossbred, Sire (ST x XB) and pen were random effects. In the W, 100% tropical steers ate less, gained less, and were less efficient (GF) than steers with some Angus breeding (P < 0.01), but not (P > 0.10) by RFI. GAin and efficiency in the S phase were not different (P > 0.05) due to tropical influence. Simple correlation between RFI of the same animal in W and S were 0.51 (P < 0.01) whereas that for GF was 0.20 (P < 0.01). Poor performance of tropically adapted steers as stockers in OK during the winter apparently resulted from a decrease in both feed intake and feed efficiency.