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Journal of Dairy Science Vol. 61 No. 2 239-245
© 1978 by American Dairy Science Association ®
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Effect of Age and Month-of-Calving on Solids-Not-Fat and Protein Yield for Five Dairy Breeds

H. D. Norman, A. L. Kuck1, B. G. Cassell and F. N. Dickinson

Animal Improvement Programs Laboratory, Animal Physiology and Genetics Institute, Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705

ABSTRACT

Lactation records of solids-not-fat or protein from herds enrolled in the National Cooperative Dairy Herd Improvement Program from 1966 through 1975 were used to study the effect of age and month-of-calving on milk, fat, solids-not-fat, and protein yields. Solids-not-fat data were in 183,282 records from 106,411 cows in 2215 herds in 41 states. Averages for Ayrshire, Brown Swiss, Guernsey, Holstein, and Jersey breeds were 8.62, 9.04, 9.13, 8.54, and 9.36% solids-not-fat. Standard deviations among cows were .45, .43, .51, .45, and .64. Averages in 21,534 lactations were 3.37, 3.54, 3.64, 3.22, and 3.89% protein, and standard deviations were .20, .26, .27, .23, and .28. Effects of herd-years accounted for a similar percentage of variation in 305-day milk, fat, and solids-not-fat yields ranging from 23 to 45% in the five breeds. Removal of effects of age raised multiple correlation squared from 5 to 18% and month-of-calving effects from 2 to 4% beyond that for herd-year. Interaction of age by month-of-calving for Guernseys, Holsteins, and Jerseys only raised multiple correlation squared from .2 to .5%, nil in Ayrshires and Brown Swiss. Because of the limited numbers of records in some breeds, the interaction of age and month-of-calving probably should be ignored to allow more precision in adjusting main effects. Adjustment factors are given for solids-not-fat for four breeds.

FOOTNOTES

1 Midwest Breeders Cooperative, Shawano, 54166.






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Copyright © 1978 by the American Dairy Science Association ®.