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Measuring Performance of Progeny of Rams in a Small Flocks¹

Massachusetts Agricultural Experiment Station and United States Department of Agriculture

Abstract

Data were collected on sheep in the Massachusetts State College flocks (Shropshire and Southdown) from 1931 to 1941, inclusive. The data on birth weight, weaning weight, slaughter score or grade (at 140 days) and type score (at 240 days) were analyzed to determine the possibilities of measuring performance of rams in small flocks.

Relationships between dams and their offspring, as measured by coefficients of correlation and regression, were low and none were large enough to be statistically significant. Adequate data were not available to make possible a valid adjustment for seasonal (year to year) variations, hence some dam-offspring relationships may have been obscured.

Differences between sires were significant or highly significant when all the data were studied without regard to seasonal (year to year) variations. A portion of the data could be used in an analysis to determine the relative importance of seasonal variations and the findings strongly suggest that much of the supposed difference between sires was caused by differences in environmental conditions from year to year.

¹ Contribution No. 465 of the Massachusetts Agricultural Experiment Station, Amherst, Mass.

² The authors are, respectively: Head, Animal Husbandry Dept., Washington State College, Pullman, and formerly Asst. Prof. of Animal Husbandry, Mass. State College; Senior Animal Husbandman in charge genetics investigations, Bureau of Animal Industry, Beltsville, Md.; Animal Husbandman, Bureau of Animal Industry, Beltsville, Md.; Asst. Prof. of Animal Husbandry, Mass. State College, Amherst. The authors acknowledge assistance of D. A. Spencer and V. A. Rice in the planning of the work and of R. C. Foley and W. F. Knight in the collection of certain of the data.