Crossbreeding dual-purpose cattle for beef production in tropical regions.

Six breed types groups of six steer calves each were used to observe differences in growth and carcass traits: F1 Brown Swiss (F1BS), F1 Holstein (F1HO), F2 Brahman (F2BR), F2 Criollo Rio Limon (F2CRL), purebred Criollo Rio Limon (CRL), and Perija Mosaic (PMO). After 404 days of grazing, the heaviest F1BS and F2BR steers were different from F1HO and CRL counterparts (p < 0.05) in slaughter weight. F2BR dressed higher and had better muscle conformation scores than F1BS, F1HO, F2CRL and CRL (p < 0.05). F1BS had the thickest backfat (0.5 cm) but only differed (p < 0.05) from F1HO (0.3 cm). Rib eye area, marbling score, carcass maturity, quality or yield grade, boneless cut percentages, bone percentage or percent trimmable fat did not vary among breed types. All steers were within the A maturity level and graded Standard. Results indicate the importance of feeding dual-purpose steers to heavier weights to please industry preferences.

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 composition of calves from Bos taurus and Bos indicus cows across different stages of growth. Hereford (H) and Brahman (B) embryos were transferred to H or B cows (n = 58) to produce purebred Brahman (BB), purebred Hereford (HH), Hereford x Brahman (HB), and Brahman x Hereford (BH) offspring. 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 fed 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 weaning 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 percentage area means from the duplicate measures. Generally, BB calves grew slowest and BH steers grew fastest (P < .05). The BH steers exhibited 15 and 20% heavier (P < .05) carcasses per day of age than H-sired steers and BB 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 unsaturation primarily were due to the percentages of monounsaturated fatty acids (MUFA). As calves became older, MUFA increased markedly, polyunsaturated fatty acids increased slightly (due to inverse, nearly proportional changes in 18:2 and 18:3), and saturated fatty acids decreased by 10 percentage units (P < .001). Thus, adipose tissue from Brahman and Hereford purebred and crossbred calves became markedly more unsaturated early postweaning; this change was less dramatic in the purebred Hereford calves.

Comparison of the fatty acid composition of subcutaneous adipose tissue from mature Brahman and Hereford cows.

The fatty acid composition of adipose tissue was measured in 37 mature Brahman and 32 mature Hereford cows to determine breed effect. Diet was held constant among all cows. When biopsied, cows were on oats and native cool-season annual pastures of good quality. Real-time ultrasound measurements of subcutaneous fat were taken at three locations (between the 12th and 13th rib, at the rump, and at the perianal region) to determine overall fatness. Overall fat thickness from these measurements was 1.3 cm for Brahman cows and 1.7 cm for Hereford cows (P < .01). Subcutaneous adipose tissue biopsy samples were collected from the perianal region, and fatty acid composition was determined using a gas chromatograph. Fatty acids were expressed in both normalized (area percentage) and gravimetric (grams/100 grams of fresh tissue) formats. In addition to greater overall subcutaneous fat thickness, Hereford cows contained 5 g more of fatty acids per 100 g of fresh adipose tissue than Brahman cows (P < .05). Subcutaneous adipose tissue from Hereford cows was higher (P < .01) in total saturated fatty acids and lower in mono- and polyunsaturated fatty acids than subcutaneous adipose tissue from Brahman cows. Compositional differences remained when breeds were compared by analysis of covariance at a common body fatness. The data suggest a genetic basis for the differences in fatty acid composition of Brahman and Hereford cows.

Growth, carcass traits, and fatty acid profiles of adipose tissues from steers fed whole cottonseed.

To investigate the impact of dietary whole cottonseed (WCS) level on fatty acid composition, growth, and carcass traits, 45 Hereford steers were assigned to diets containing 0, 15, or 30% dietary WCS. The 15 and 30% WCS contributed an estimated 3.3 and 6.6% additional lipid, respectively, to the diets. After being fed for 54 d, all animals were weighed and slaughtered, and carcass measurements were obtained. There were no differences (P greater than .05) among dietary treatment groups in live weight or ADG for the 54-d feeding period. Control steers had larger (P less than .05) longissimus muscle areas than steers fed 30% WCS, which accounted for the advantage in yield grade (P less than .05) exhibited by the control group. Feeding of 30% WCS resulted in minor increases in linoleic and total polyunsaturated fatty acid content of perinephric fat expressed in both normalized (area percentage) and gravimetric (g/100 g of fresh tissue) formats. There were no significant differences in the monounsaturated or saturated fatty acid content of adipose tissues from animals fed the different diets. Subcutaneous adipose tissue samples were higher (P less than .01) in total unsaturates but had lower (P less than .05) proportions of C18:0 and C18:1 than perinephric samples. Feeding WCS at the levels reported herein only had minor effects on fatty acid composition of beef adipose tissues.