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Injection1The Upjohn Company,2, Kalamazoo, Michigan 49001, , Michigan State University,3, East Lansing 48823, , University of Florida,4, Gainesville 32601, and and Louisiana State University,5, Baton Rouge 70803
Abstract
Cattle were randomly assigned on a stratified basis to one of three treatments at each of four locations such that similar numbers of cattle were assigned to each treatment. Cattle assigned to Treatment I (controls) were observed for estrus at least twice daily and inseminated at estrus detected during an 18- to 25-day interval. Cattle assigned to Treatments II and III were injected with 30 mg Prostaglandin F2
-THAM salt (PGF2-THAM salt) if a corpus luteum (CL) was detected by rectal palpation or assumed to be present based on a previous palpation. Cattle assigned to Treatment II were observed for estrus at least twice daily and inseminated at estrus detected during days 1 through 7 after PGF2. Cattle of Treatment III were inseminated twice at about 72 and 90 hr. after PGF2. Pregnancy was diagnosed by palpation at 35 to 60 days after insemination. Percent cattle pregnant was based on number of cattle inseminated for Treatments I and II and number of cattle responding to PGF2 and inseminated for Treatment III. Percent pregnant and number of cattle inseminated were 53.3 and 122, 52.2 and 69, 55.8 and 86 for Treatment I, II, and III, respectively. Differences in fertility among the three treatments did not approach significance. Thus, 1) fertility was similar to controls when cattle were inseminated at synchronized estrus following PGF2 and 2) fertility was similar to controls when cattle were inseminated at predefined intervals following PGF2.
Administration of prostaglandin F2 (PGF2) to cows after but not before 5 days after estrus was followed by decrease in serum progesterone (Louis, Hafs and Seguin, 1973), decrease in size of the corpus luteum (Louis et al., 1973), and return to estrus at about 3 days (Rowson, Tervit and Brand, 1972; Lauderdale, 1972; Louis et al., 1973; Inskeep, 1973). Fertility appeared to be normal, based on limited numbers of cows, either for cows treated with PGF2 and given embryos transferred from donor cows, (Rowson et al., 1972) or for cows inseminated at estrus following PGF2 (Inskeep, 1973).
The purpose of this study was to investigate more extensively the fertility of cattle inseminated after PGF2 injection. The study was conducted cooperatively at Michigan State University (M), University of Florida (F), Louisiana State University (L), and The Upjohn Company (U). A cooperative study utilizing cattle of differing genetic bases managed under different environmental conditions should yield a more reliable estimate of fertility than could be obtained from a single location. A portion of these data has been presented previously (Lauderdale et al., 1973).
1 Appreciation is expressed to Dr. Harold Hafs for assistance in design, Dr. H. D. Ritchey, Dr. W. D. Oxender, Mr. R. J. Kittok and Mr. T. M. Louis for assistance in executing the study, to Dr. S. Geng for assistance in statistical analyses, and to Mr. W. W. Bassett and Bassett's Dairy, Monticello, Florida, for allowing use of his dairy herd.
2 Agricultural Research and Development.
3 Department of Dairy Science.
4 Department of Dairy Science.
5 Department of Animal Science.
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