Repeatability of Production in Range Beef Cows

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Abstract
The data investigated were 603 weaning wts. and 620 birth wts. of calves produced by 151 range Hereford cows in the exptl. herd at Still-water during the 8-year period from 1944 through 1951. Also, weaning wts. and birth wts. of 98 calves from 49 cows at the Fort Reno Expt. Sta. were analyzed. Effects on birth and weaning wts. of age of calf, sex of calf, age of dam and year were studied, and correction factors devised to adjust wts. to a comparable basis. Gains from birth to weaning were detd. by subtracting corrected birth wts. from corrected weaning wts. For the group of cows at Stillwater, all of which calved first at 3 years of age, repeatability was detd. by 2 methods: intraclass correlation between wts. or gains of calves produced by the same cow and regression of later records from the 1st toward the herd avg. Estimates of repeatability were as follows: for weaning wt. 0.43 and 0.49, for birth wt 0,18 and 0.14, for gain from birth to weaning 0.38. For the group of cows at the Fort Reno Station, all of which calved first at 2 years of age, the correlation between weaning wts. of 1st and 2d calves was 0.66. The correlation between birth wts. of 1st and 2d calves was 0.25, and the correlation between gains from birth to weaning of 1st and 2d calves was 0.69.