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Differences in Lifetime Productivity of Herefords Calving First at 2 and 3 Years of Age¹

Mississippi State University, Mississippi State 39762

Abstract

Eighty weanling Hereford heifers selected for similarity in size and age were started on test in November 1965. One-half of the heifers was assigned to a winter regime consisting primarily of well fertilized wheat and ryegrass pasture and the other half to a drylot wintering regime of high quality corn silage. The treatments were imposed for the first two winters of the test which ranged from 1965 to 1975. One-half of the heifers in each treatment group was bred to calve either at 2 or 3 years of age. Response variables were spring and fall cow weights, calving percent and day, calf birth and weaning weight, weaning percent and percent cows leaving the herd each year. Age at first calving affected (P<.001) cow weights only. There was an interaction between calving age and treatment in the cow weight analyses. Differences in subclass mean weights varied in magnitude, but means did not change rank from treatment to treatment. From examining the products of weaning percentages and weaning weight it is apparent that calving first at 2 years of age was a satisfactory practice in this experiment.

¹ Mississippi Agricultural and Forestry Experiment Station Journal Article No. 3706.

² Department of Animal Science.

³ Brown Loam Branch Experiment Station, Raymond, MS.