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.

Using live animal ultrasound measures of ribeye area and fat thickness in yearling Hereford bulls.

Ultrasonic measurements of fat thickness (FAT) and ribeye area (REA) were analyzed together with weight (WT), scrotal circumference (SC) and age data from 385 yearling Hereford bulls representing 45 sires. Additional variables created were 100*REA/WT (REACWT) and 365-d adjusted REA (AREA). Multiplicative age adjustment for AREA was calculated from linear regression of REA on age. Heritabilities were .45 +/- .17 for REACWT, .36 +/- .16 for WT, .12 +/- .13 for REA, .11 +/- .13 for AREA, .04 +/- .13 for FAT and .18 +/- .14 for SC. Phenotypic and genetic correlations were strongly negative for WT with REACWT. Neither AREA nor REACWT alone were considered suitable muscling variables due to their association with age, WT and FAT. Ultrasound REA measurements should be adjusted for the linear effects of age and WT and quadratic effects of FAT before being used for selection. Measurement of SC indicated a strong association with WT (r = .55) and a moderate positive genetic correlation with REA (.49 +/- .58).