Estimates of mature weight (A) and maturing rate (K), determined by asymptotic regression, were studied to evaluate the effects of using quarterly weights taken in different seasons of the year for estimating growth curve parameters. Quarterly weights of 102 Angus cows were used to calculate eight sets of weight-age curves. Four sets of estimates were calculated from weights from birth to 5 yr of age (FIVE-YEAR curves) and four sets were calculated from all weights collected throughout the life of each cow (LIFETIME curves). Within each age group, one set of parameters was estimated from all weights up to the respective ages (FIVE-YEAR and LIFETIME). The other three sets, within each age, were based on quarterly weights from birth to 1 yr of age plus one weight/year taken during the summer, fall or winter. The symbols A and K were used with the following subscripts: 0 or 5 as a first digit to represent weight-age parameters estimated from all weights taken during the life of the cow and from weights taken before the cow was 5 yr old, respectively; and 0, 2, 3, or 4 as a second digit to represent all quarterly weight, summer, fall or winter weights, respectively. Mean estimates of mature weight were 496, 492, 492, 522, 483, 478, 487 and 508 kg for A00, A02, A03, A04, A50, A52, A53, and A54, respectively. Season of weighing affected both A and K. Coefficients of correlation among the estimates of mature weights were all positive and larger than .70. Coefficients of correlation among estimates of rate of maturing were larger than .50, except those involving the correlation of K00 and FIVE-YEAR estimates. This study indicates that weight-age characteristics estimated from quarterly weights from birth to 1 yr of age and a single annual weight from 1 to 5 yr are adequate for estimating practical weight-age parameters at an early cow age. However, in FIVE-YEAR estimates, the effect of a cow's being nonpregnant at 2, 3 or 5 yr of age and, in LIFETIME estimates, any open year, especially the terminal year, may result in serious bias.
A total 262 Angus steer calves averaging 207 kg from none (trial 1) and five farms (trial 2) were identified on the farm of origin and one-half of the calves on each farm was implanted with 36 mg of zeranol before entering the feeder calf assembly and marketing system. Calves were assembled, fasted for 24 h and fed hay for 72 h, then shipped 1,368 km. Upon arrival, the following receiving diets were fed for 4 wk to one-third of the calves from each farm and implant group: 1) control diet, 2) high-potassium diet, 3) escape-protein diet using corn gluten meal, which can escape ruminal degradation as a protein source. Implanted calves gained more weight (P less than .10) than nonimplanted calves while on the farm, but changes in weight during assembly, transit and the 28-d receiving period were not different (P more than .10). Plasma glucose and total protein concentrations were higher (P less than .05), while urea nitrogen concentration was lower (P less than .05) for implanted calves following transit. Increasing the potassium concentration of the receiving diet increased (P less than .05) post-transit weight gains, but had no affect on dry matter consumption. Corn gluten meal replaced soybean meal in the escape-protein diet and resulted in similar weight gains. Plasma urea nitrogen concentrations were higher (P less than .05) at 2 wk post-transit in the escape-protein diet group as compared with the control group. Receiving diet had no effect on the incidence or severity of bovine respiratory disease, but affected (P less than .05) performance during the subsequent 69-d stocker phase of ad libitum access to medium quality hay and 2.27 kg of supplement per day.
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