Graduate Thesis Or Dissertation
 

Embryonic mortality in pubertal gilts

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  • An experiment was conducted to compare the reproductive performance and serum concentrations of progesterone and estrogen of mated first (n=18) and third (n=18) estrous gilts slaughtered in equal numbers on days 3, 15 and 30 postmating. Fertilization rate did not differ between mated first and third estrous gilts. Embryonic survival was consistently lower (P<.05) among mated first versus third estrous gilts. Ratio of progesterone to estrogen was higher among gilts bred at first versus third estrus on days 15 and 30 but lower on day 3 (stage of gestation x estrous period interaction, P<.05). Altered ratio of systemic levels of progesterone and estrogen may be related to early embryonic mortality in mated first estrous gilts. Day 3 porcine embryos collected from first and multiestrous donors were transferred into synchronous nonmated first (n=40) and third (n=37) estrous recipients to assess influence of uterine environment on embryonic survival in pubertal gilts. Percentage survival of embryos in first and third estrous recipient was not different. However, percentage survival of embryos from multiestrous donors was higher than those from first estrous donors. Embryonic mortality in mated pubertal gilts is likely due to defective ova instead of a hostile uterine environment. Influence of early ovulation on embryonic survival in first estrous gilts was examined. Gonadotropin releasing hormone (GnRH) was injected intravenously into 10 pubertal gilts after initial mating on first day of detected estrus; control pubertal gilts (n=10) were similarly injected with physiological saline. Blood samples were collected prior to injection, thereafter at 15 minute intervals for 90 minutes and subsequently on day 30 of gestation; sera were analyzed for luteinizing hormone (LH) and progesterone. Treatment with GnRH increased secretion of LH during the 90 minutes after injection (P<.05). Ovulation rate was higher in treated than control gilts (P<.05) but embryonic survival and serum progesterone concentration were not enhanced on day 30 of gestation. Increased ovulation rate induced by GnRH is not accompanied by an increase in embryonic survival.
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file details ArchibongAnthonyE1988.pdf 2017-08-16 Pubblico Scaricare