Effect of administration of progesterone and oestrogen on litter size in pigs

Abstract

Summary. Progesterone and oestrone alone or in combination were administered to sows during early gestation. A dose of 25 mg progesterone and 12\m=.\5 \g=m\g oestrone injected together for 10,5 or 2 consecutive days during the implantation interval caused increased litter size at term.The effect of exogenous steroid hormones on embryonic survival in the pig is unclear. While pro¬ gesterone given alone during gestation has no, or even a detrimental effect on embryo viability (Sammelwitz, Dziuk & Nalbandov, 1956;Haines, Warnick, Wallace & Edwards, 1957;Spies, Zimmerman, Self & Casida, 1959), the administration of progesterone and oestrogen has been re¬ ported to increase embryo survival (Reddy, Mayer & Lasley, 1958;Day, Romack & Lasley, 1963 Progesterone (A*-pregnen-3,20-dione: Sigma Chemical Co.) and oestrone (A1,3,5(10)-estratrien-3-ol-17-one: Sigma Chemical Co.) solutions were prepared as described by Reddy et al. (1958) and injected i.m. in volumes of 2 or 4 ml at invervals of 23-25 hr. The control and hormone treatments used are shown in Table 1. Control animals received cottonseed oil at corresponding times of treat¬ ment administration, but because there were no differences in mean litter size in the various subgroups, these results were pooled into one control group (Group 0).The number ofsows returning to oestrus, the number carrying the litter to term and the total number of pigs farrowed were recorded. Mean litter size was calculated and statistically tested by least squares regression analysis (Harvey, 1960).Conception rate was high in all treated sows and did not differ from that in controls. There was no effect of breed of sow or individual boar on litter size results (least squares regression analysis). As shown in Table 1, there was a significant increase in litter size when progesterone and oestrone were administered from Days 14-23 (Group 2), a period during which implantation is occurring (Green & Winters, 1946). Administration of both steroids for shorter intervals at this time resulted in increased litter size only in Groups 4 and 6. There was no effect of treatment on the number of pigs stillborn.

Endocrine Effects of GnRH Agonist Application to Early Pregnant Gilts

“…Whether or not FSH contributes to influence luteal function remains speculation. If we were to accept previous reports that steroid treatments in pigs [8,9] or GnRH in horses [30,31] benefit pregnancy outcome, other routes of GnRH mediation could also be evident, such as those influencing processes of uterine estrogen synthesis [32], endometrial angiogenesis, utero-ovarian counter-current transfer [33] and P4 dependent immunomodulation [34,35]. Furthermore, direct effects of GnRH on ovarian luteal cells [36] and on uterine tissues mediated by extrapituitary receptors should be recognized [37,38].…”

“…Attempts have been undertaken to improve pregnancy rate or reduce pregnancy losses in pigs by steroid or gonadotropin application [5][6][7]. Since steroid treatment may improve litter size [8,9], the question is whether luteal P4 secretion can be enhanced by GnRH-induced LH stimulation. This is because LH is considered to be essential in pigs for support of luteal P4 production and pregnancy outcome as demonstrated by passive immunization with anti-LH serum or blockage of LH secretion and regulation of ovarian function by a GnRH antagonist [10,11].…”

The Relationships between Plasma Progesterone and LH and the Numbers of Corpora Lutea and Embryos in Purebred and Crossbred Gilts

“…Studies to determine the effects of exogenous progesterone on embryonic survival are not conclusive (Day et aL, 1959;Spies et al, 1959;Schultz et al, 1966;Wildt et al, 1976). Studies of the relationship between plasma progesterone concentrations or progesterone metabolites in the urine and embryo numbers have yielded inconsistent results (Mayer et al, 1961;Tillson and Erb, 1970;Edgerton et al, 1971;Rampacek and Ulberg, 1973).…”

Chorionic surface area in conceptuses from sows treated with progesterone and oestrogen during early pregnancy

“…The results of two field trials undertaken by Wildt, Culver, Morcom & Dukelow (1976) also indicated that treatment of sows with progesterone and oestrone (2000:1) during early pregnancy had a beneficial effect on embryo survival, although the findings were not wholly unequivocal. In the main trial, an increase of approximately 20% in litter size at birth was recorded in the treated animals, but in a second trial no significant difference was observed between the treated and control groups.…”