MILK PRODUCTION IN RANGE BEEF COWS AND ITS RELATIONSHIP TO CALF GAINS

Abstract

Milk yield in lactating range beef cows was estimated by milking 42 cows four times at approximately monthly intervals during the lactation. Milking was by machine after oxytocin injection. Weights of calves, before and after suckling, over a 24-hour period were used to estimate calf consumption. Breed-age group averages for 24-hour milk yield varied from 3.7 to 8.4 kg, with an overall average of 6.4 kg. Breed of cow accounted for 82.5% of the variance in milk yield in these data. Milk yield declined on the average by 0.02 kg per day of lactation. The correlation between calf consumption and milk yield was 0.58. Butterfat was 3.9% on the average, protein 3.5%, solids-not-fat 9.1% and total solids 13.0%. Breed-age group or month of test did not significantly influence milk constituent percentages, although butterfat and total solids tended to rise as lactation progressed.A good estimate of milk yield was obtained by one test milking. Milk composition based on one test milking was not reliable. Milk yield as estimated in any month was highly related to calf average daily gain from birth to weaning. Use of two test milkings improved the relationship only slightly. Milk solid component percentages showed little relationship to calf gains.