Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Robert C. Lamb


Robert C. Lamb


David Marcinkowski


Bruce Godfrey


Heifers should represent the greatest genetic potential within a dairy herd. To maximize this potential, heifers must be inseminated to proven sires, a practice requiring management changes on many dairies. Holstein heifers (n=115) were allotted to one of three groups to compare alternatives to daily estrous detection that may facilitate the management of a program of artificial insemination for heifers. Group 1 heifers (Controls) received no treatment but were observed twice daily for signs of estrus. Group 2 heifers (2X-PGF) were synchronized with two injections of prostaglandin F2 alpha given 11 days apart and observed for estrus. Group 3 heifers (MGA+PGF) were synchronized with 9 days of melengestrol acetate feeding and an injection of prostaglandin F2 alpha 14 days after the last feeding and observed for estrus. Comparisons were made on the effectiveness of each treatment in estrous response and pregnancy rates and on the management requirements and economics associated with each program. Estrous response was significantly higher for the 2X-PGF group, while synchronized pregnancy and first-service conception rates did not differ. On an annual basis, the MGA+PGF group was calculated to require three-quarters of the labor input as compared to the 2X-PGF group and less than a fifth of the labor required for the Control group. A program of daily estrous detection was calculated to have an economic advantage over synchronization the frequency estrous synchronization programs was scheduled four times per year. was increased to six times per when When year, synchronization had a slight economic advantage over daily estrous detection when animal numbers were low and labor costs were high. The economic advantage of daily estrous detection is reduced when synchronization is performed more frequently throughout the year.



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