Masters Theses

Date of Award

8-1963

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

E.W. Swanson

Abstract

During the first few weeks of a dairy cows' lactation the milk production rises to a maximum then gradually declines as the lactation progresses. Lactations showing a slow decline are said to have higher persistency than lactations showing a rapid decline in production. Although lactations vary in persistency the production of all cows declines as the lactation progresses. This decline in production combined with the physiological necessity of a dry period makes it necessary for the cow to be bred at regular intervals thus re-establishing the high post-calving level of production. It can be shown that the calving interval which offers the most economic benefit is one which balances the loss of production during the dry periods with the gain in production due to the postcalving peak. Obviously cows with lactations of low persistence need a shorter calving interval than cows with lactation intervals of high persistence, but for the sake of convenience of management and standard-ization of records, a calving interval of twelve months is usually adopted. One of the problems facing the dairy farmer in his attempt to keep his cows to the most economical calving interval is getting the cows to conceive at the right time. For this reason any method of improving the conception rate would find great practical application. To maintain a twelve-month calving interval the cows must be bred as soon as possible after sixty days postpartum. It is entirely possible that the uterus is not in a suitable condition to provide optimum con-ditions for sustaining a pregnancy at this time. This experiment was designed to examine the possibility of improving the conception rate in dairy cattle by inducing an early postpartum estrus with hormone injections. The relationship between the rate of uterine involution and conception rate was also studied.

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