Intrauterine Development of the Bovine Fetus in Relation to Milk Yield in Guernsey Cattle

Experienced physicians and others who come in contact with obstetrical work in man or animals frequently hold the opinion that the development of the fetus is a serious drain on the animal organism. If this animal happens to be in milk production this supposed drain is said to produce a marked depression in the animal's milk yield. In view of the wide credence placed in this hypothesis it is surprising to find that the experimental evidence presented in its support is so slight. The American Guernsey Cattle Club in volume 31 of their advanced registry furnished data on the milk yields and length of time the calf is carried by the cows during the 365-day lactation in which the cows are making their record. These data are analyzed in the following paper to determine the vah'dity of the hypothesis indicated above. CORRELATION BETWEEN THE MILK YIELD AND DURATION PREGNANCY AND BETWEEN THE BUTTER-FAT PER-CENTAGE AND DURATION OF PREGNANCY OF The data are divided into periods of six months according to the age of the cow thus eliminating any marked influence of the cow's age on her milk yield. Cows on advanced registry tests are generally bred in or after the fourth month of lactation, the 1 Papers from the Biological Laboratory of the Maine Agricultural Experiment Station, No. 156. The Rockefeller Institute for Medical Research has furnished material aid to these animal husbandry investigations in the form of a grant for increased maintenance of the work. This paper presents one phase of these researches as conducted by the Biological Laboratory of the Maine Agricultural Experiment Station.