LIFETIME PRODUCTIVITY OF PUREBRED AND CROSSBRED COWS OF ANGUS AND MILKING SHORTHORN PARENTAGE
Abstract
Lifetime productivity of crossbred Angus (A) by Milking Shorthorn (M) cows was studied using data on 242 cows of AA, AM, MA and MM breed groups. Cows were born in the fall over a 5-year period from 1966 through 1970. Data from parities one through six were analyzed separately for each parity by the method of least squares. Parities seven through thirteen were combined in one analysis with the effect of parity added to the model. Appropriate contrasts of estimates of breed means provided estimates of genetic effects (individual additive, maternal additive, individual heterosis, maternal heterosis, and grandmaternal) on calf weights and viability and on cow weight, condition score, pregnancy and weaning rates and efficiency of production. Data describing weights, gains, grades and viability of calves and weights, gains, livability and reproductive rates of cows were derived from data describing lifetime performance of cows of AA, MM and AM/MA breed groups and their calves. These data were utilized to estimate economic efficiency of each of the three breed groups at each combination of three forage values and three calf values. Crossbred cows were 22.8 kg (5.8%, P < .01) heavier and scored .15 condition units higher (5.3%, P < .01) than purebred cows. Pregnancy and weaning rates were higher (2.9%, P < .05 and 45.9%, P < .01, respectively) for crossbred than purebred cows. Calves from crossbred cows had 6.3% greater (P < .01) viability, and 4.7% heavier (P < .01) weaning weights than calves from purebred cows. Heterosis contrast for efficiency of production was 3.4% (P < .01) and represented 8.0% superiority for crossbred cows. Longevity averages of AA, MM and AM/MA groups, respectively, were 5.65, 4.58 and 5.80 years of age. Replacement rate for MM cows was higher (21.8%, P < .01) than for AA cows (15.7%) and AM/MA cows (13.6%). The herd income above feed cost and replacement value at age equilibrium indicated that crossbred cows had a larger profit margin than either purebred group.
Degree
Ph.D.
Subject Area
Genetics
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