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Relationship of Dam's Weight and Weight Changes to Calf's Growth Rate in Hereford Cattle¹

North Carolina Agricultural Experiment Station, Raleigh³

Abstract

Four hundred nine records on Hereford cattle were analyzed to study the relationship between dam's changes in weight during the last third of gestation and the first six months of lactation with calf's birth weight and calf's gain in different periods, from birth to 180 days. The relationship of calf birth weight to calf gain up to 180 days also was studied.

On the average cows lost weight during the period from 90 days before calving to right after calving and during the first 60 days of lactation and gained thereafter. Heavier cows 90 days before calving tended to produce heavier calves at birth and throughout the suckling period. Calf's birth weight was the variable most closely associated with calf's gain. This relationship increased with the age of the calf.

The pattern of change in weight by the dams was subject to herd and age effects. In the youngest dams cows producing the faster gaining calves showed smaller loss in weight during the last 90 days of gestation and during the first 60 days of lactation and higher gains during the remaining part of the lactation period. Older cows gave birth to heavier calves, and dams which produced the faster gaining calves tended to have larger weight losses during the first 60 days of lactation, but gained more thereafter.

As the calf grew older, the dam's weight 90 days before calving became less important as a determinant of its weight gain. The calf's birth weight was the most valuable predictive measure of its gain up to 180 days of age.

¹ Contribution from the Department of Animal Science, North Carolina Agricultural Experiment Station, Raleigh, North Carolina. Published with the approval of the Director of Research as Paper No. 2163 of the Journal Series. Conducted in cooperation with the Southern Regional Project S—10, The Improvement of Beef Cattle for the Southern Region through Breeding Methods.

² Present address: Estacion Experimental Agricola La Molina, Lima, Peru.

³ The computing services for this investigation were supported by NIH Grant No. FR-00011.