Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 28, 2004
Publication Date: February 5, 2005
Citation: Ferrell, C.L., Jenkins, T.G., Freetly, H.C. 2005. Feed utilization and performance of tropically adapted cattle [abstract]. Journal of Animal Science 83(Suppl. 2): 28. Technical Abstract: Four studies were conducted to evaluate tropically adapted breeds for feed utilization and energy use during growth. In study 1, 10 Bos indicus (5 Boran, Bo; 5 Brahman, Br) sired and 10 MARC III steers were used in a 2 × 2 factorial design to assess cattle age and breed influence on digestion of a high grain diet. Duodenal flows of total N, microbial N, nonmicrobial N, total amino acids, and total tract N digestibility were not different (P>0.05) due to age or breed. In study 2, ¼ (21), ½ (7), and ¾ (9) Br were compared to MARC III (14) steers fed bromegrass hay or corn silage diets during a 119 d period. Br crosses ate less (6.62 vs. 7.41 kg/d) and grew slower (0.62 vs. 0.72 kg/d) than MARC III (P<0.05), but ME/gain was similar (35.2 vs. 31.1 Mcal/kg; P=0.40). When subsequently fed a high-corn diet, daily DM intake (7.63 vs. 8.49) and ADG (1.18 vs. 1.32 kg/d) were lower (P<0.05) for Br steers. Br and MARC III had similar ME/gain during finishing (20.2 vs. 20.2 Mcal/kg; P=0.98) and for the entire study (21.6 vs. 21.4; P=0.79). Influences of Angus (A), Bo, Br, Hereford (H), and Tuli (T) sires on body composition and energy use during finishing was evaluated in study 3. Feed intake was least for Bo- and T-, intermediate for Br- and H-, and greatest for A-sired steers. Rates of weight, fat, and energy gains were similar for A-, H-, and Br-sired steers, but less (P<0.01) for Bo and T when fed ad libitum. Liver weights differed (P<0.01) among sire breeds (6.33, 4.55, 5.06, 6.09, and 4.87 kg for ad libitum fed A, Bo, Br, H, and T) and increased in response to increased daily feed intake in H (0.65), A (0.55), Bo (0.47), Br (0.38), and T (0.40). Maintenance and efficiency of energy use for gain differed (P<0.05) among sire breeds. In study 4, fasting heat production (FHP) at 30 wk of age was highest for MARC III heifers and decreased as Br increased (0, ¼, ½, ¾). FHP decreased with aging, but the rate of decrease followed the same ranking, resulting in similar values at 86 wk. A number of differences between tropically and temperately adapted cattle were observed, but efficiency of feed use was similar.