The effect of body weight, hip height and subcutaneous fat thickness on winter and spring-summer pasture performance and subsequent feedlot performance of beef steers

Fall weaned steers (112), of Hereford, Angus, or Hereford X Angus breeding, plus 75 steers of mixed breeding (British X or British X Continental) were utilized to investigate the effects of fall body measurements on winter weight change, spring/summer grazing performance, and subsequent feedlot performance. The steers were wintered on either permanent pasture (fescue and/or orchardgrass plus clover) or winter annual pastures (rye, ryegrass, plus clover) and were afterwards allowed grazing periods ranging from 94 to 167 days. Following the pasture phase, cattle were assigned to slaughter groups and serially slaughtered following 0, 28, 56, 84 or 112 days on a full feed ration consisting of whole-shelled corn plus 36% protein supplement (Tend-R-Leen®).

Analysis of variance and multiple regression analyses were conducted to determine factors that had significant effects on grazing data and carcass traits. Steers that performed best under grazing situations were those described as lighter in weight and taller at the hips. Those managed for greater winter gains were heavier at the end of spring/summer grazing. Measures of carcass production (feedlot average daily gain, carcass weight [CARWT] and rib eye area) were positively associated with purchase weight (PURWT), initial hip height (INHH), and days on feed. Measures of carcass fatness and quality (external carcass fat, quality grade [QG], yield grade [YG] and kidney, heart and pelvic fat) were generally increased with increases in PURWT, initial fat (INFAT) and weight gain during grazing treatments and were negatively associated with INHH.

Prediction equations for three variables (CARWT, QG, YG) were simultaneously solved to determine values for PURWT, INHH, and INFAT that would meet the following limitations: (1) CARWT = 700 lbs.; (2) QG = low choice; and (3) YG = 2.5. At Martin, the "ideal" steer at weaning weighed 771.71 lbs., measured 44.95 inches at the hips and carried 4.07 mm of external finish. The most desirable carcass limitations for Crossville cattle (of British breeding) were the following: (1) CARWT = 650 lbs.; (2) QG = low choice; and (3) YG = 2.5. Weanling cattle that would satisfy these limitations weighed 665.78 lbs., measured 38.65 inches at the hips and carried 3.69 mm of external finish. These cattle averaged gaining .77 Ib./hd./day and .86 Ib./hd./day at Martin and Crossville, respectively.