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The Effect of the Ages of Sire and Dam on the Average Butterfat Production of Offspring in Dairy Cattle^*

Department of Dairy Husbandry, University of Missouri, Columbia

ABSTRACT

Since early times many breeders, from their observations of dairy cattle, have concluded that immaturity and senescence of parents have a marked effect upon the milk and butterfat production of the progeny. Considering the economic importance of the effects of these factors upon the dairy industry, there has been a very scant amount of analytical consideration given to determine any variations in the performance records of progeny due to different ages of parents.

It is well known that the age of parents affect fecundity, and birth weights in domesticated animals, and many investigators believe that sex-ratios are also affected by the same influences. Carmichael and Rice (3) in their study of fecundity in swine found that there was a gradual increase in the size of the litter as the sows grew older up to the time they were three years of age, after which the tendency for decrease in litter size became apparent.

^* Received for publication August 1, 1927.