FATTY-ACID COMPOSITION OF SUBCUTANEOUS ADIPOSE-TISSUE FROM MALE CALVES AT DIFFERENT STAGES OF GROWTH

The objective of this investigation was to compare fatty acid composit ion of calves from Bos taurus and Bos indicus cows across different st ages of growth. Hereford (H) and Brahman (B) embryos were transferred to H or B cows (n = 58) to produce purebred Brahman (BB), purebred Her eford (HH), Hereford x Brahman (HB), and Brahman x Hereford (BH) offsp ring. Calves were castrated at 2 to 3 wk of age. Before weaning (210 d of age), calves were fed native grasses. After weaning, calves were f ed a concentrate diet in dry-lot pens. Adipose tissue was obtained by biopsy at two times: at weaning during forage feeding and 3 mo after w eaning when placed on feed. A third sample was collected from the fed steers at slaughter (approximately 430 d of age). Samples obtained by biopsy and after death were collected from the perianal region. Fatty acid composition for each sample was determined as the normalized perc entage area means from the duplicate measures. Generally, BB calves gr ew slowest and BH steers grew fastest (P < .05). The BH steers exhibit ed 15 and 20% heavier (P < .05) carcasses per day of age than H-sired steers and BE steers, respectively. Adipose tissue samples from calves from Brahman sires or dams were less saturated (P < .05) than samples from calves from Hereford sires or dams. Differences in degree of uns aturation primarily were due to the percentages of monounsaturated fat ty acids (MUFA). As calves became older, MUFA increased markedly, poly unsaturated fatty acids increased slightly (due to inverse, nearly pro portional changes in 18:2 and 18:3), and saturated fatty acids decreas ed by 10 percentage units (P < .001). Thus, adipose tissue from Brahma n and Hereford purebred and crossbred calves became markedly more unsa turated early postweaning; this change was less dramatic in the purebr ed Hereford calves.