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Seasonal Distribution of Twin Births in Cattle¹

Wisconsin Agricultural Experiment Station

Abstract

Numerous influences may affect the fecundity of mammals as measured by the number of young produced. These may be inherent factors, that is, dependent on the heredity of the species, breed, or individual concerned; they may be environmental; or they may be directly physiological. As an illustration of the last may be mentioned the well established tendency for females to produce more offspring at a birth as they grow older, at least up to a certain limit.² The common practice of "flushing" ewes³ to increase the lamb crop may serve as an illustration of environmental effect on observed fecundity, while the inherent difference in fecundity in different breeds or families of livestock is too well known to require special mention.

Scope of Investigation

The data compiled by Jones and Rouse (loc. cit.) seemed especially favorable for determining whether there is any definite relation between observed fecundity in cattle and the season of the year.

¹ Papers from the Department of Genetics, Agricultural Experiment Station, University of Wisconsin, No. 53. Published with the approval of the director of the station.