Determination of conception and embrionic loss rate by Monitoring Peripheral Serum Progesterone Levels in Heifers Induced Their Estrus with Cloprostenol

In this study, 80 Holstein heifers were assigned to two groups as treated (n=60) and control (n=20). While the treated heifers were received 526 microgram cloprostenol sodium at day 12 of estrus cycle, heifers in the control group were inseminated at the first detected spontaneous estrus. In the treated group, observation of the estrual activity of heifers were maintained for 96 hours following administration of PGF2 a and they were inseminated approximately 12 h after the initial observation of estrus. In this group, heifers which had not been showed the estrual activity until 72 h were inseminated at 72 and 96 h after PGF2 a injection. Blood samples for progesterone assay were drawn from jugular vein puncture 2 times weekly between the days 22 and 60 of the gestation.

While 93.4 percent out of heifers receiving PGF2 a did exhibit behavioral estrus within 72 h , the remaining heifers in treated group (6.6%) didn`t show standing heat. In treated group, while the pregnancy rates of heifers exhibited the standing heat were 71%, in contrast, heifers that had failed to respond with behavioral estrus to injection were 25% in the first service. Whereas conception rate of treated group was 80 percent at day 22, pregnancy rate was fell to 68.3 percent at day 60. Untreated control heifers in the same herds achived a 95% conception and 90% pregnancy rate. As heifers with a serum progesterone concentration of 2.0 ng /ml or higher were considered pregnant, there was an apparent loss of seven pregnancies in the treated group between 22-45 day postinsemination as compared to one loss in the control group (p <0.01). Six out of these seven heifers which had embrionic loss were showed a marked decrease of progesterone levels on day 22 and day 27 after insemination as compared to heifers which had normal pregnancy at similar pregnancy time ( p <0.05). While heifers began to decline the progesterone levels at day 22 of the pregnancy were exhibited behavioral estrus 3- 5 days later, after day 30 of the pregnancy , estrus were observed 6-27 days later.

These study results had been indicated that heifers treated with PGF2 a at day 12of the estrus cycle could be had lower pregnancy rate as compared with untreated control, that embrionic death could be detected to monitor peripheral serum progesterone concentration on day 22, 27 and 30 of pregnancy and also that the interval between the onset of luteal regression and behavioral estrus in embrionic loss could be varied among 3-27 days . Keywords : Embrionic Death, Heifer, PGF2 a, Serum Progesterone