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Weaning Weight Related to Subsequent Most Probable Producing Ability in Hereford Cows¹

Montana State University, Bozeman, 59715

Abstract

Data on 3,342 calves and 648 cows from seven lines of Hereford cattle were collected at the Northern Agricultural Research Center, Havre, Montana. The objective of the study was to investigate the phenotypic relationship between measures of early growth rate and most probable producing ability for 180-day weight [MPPA (180W)]. Estimates of repeatability for birth weight and 180-day weight were 0.27±.02 and 0.44±.02, respectively. These estimates were used in the calculation of MPPA values for the two traits.

The overall phenotypic correlations of 180-day weight and postweaning ADG with MPPA (180W) were 0.15 and –.01, indicating that the phenotypic relationship between early growth rate and MPPA (180W) tended to be positive. Year of birth, age of dam and birth date had a significant effect on the cow's MPPA (180W). These environmental sources of variation tended to effect a negative relationship between early growth rate and MPPA (180W), indicating that at least a part of the environmental portion of the phenotypic relationship between early growth rate and MPPA (180W) was negative. Cow line, a genetic source of variation, had a significant effect on MPPA (180W) and 180-day weight, and contributed positively to the relationship between 180-day weight and subsequent MPPA (180W).

¹ Conducted in cooperation with Western Regional Research Project W-1, The Improvement of Beef Cattle Through the Application of Breeding Methods. Published with approval of the Director of the Montana Agricultural Experiment Station, Journal Series No. 310.

² The authors wish to acknowledge the supervision of record collection by F. S. Willson, A. E. Flower, J. J. Urick and C. Windecker and the computer programming assistance of E. P. Smith and V. R. Stewart.