Systemic and local hormonal requirements for implantation in domestic animals

Relationships among uterine and placental factors in prolific ewes and their relevance to variations in foetal weight

Observations were made on the distribution of ovulations between the two ovaries, the distribution of foetuses between the two uterine horns, the total numbers of cotyledonary burrs, and the weights and numbers of foetal cotyledons for each foetus in 80 Finnish Landrace × Dorset Horn ewes killed between 50 and 145 days of gestation. While ovulations were randomly distributed between right and left ovaries, viable foetuses were more evenly distributed between right and left uterine horns. Migration of embryos between the horns contributed to this relative balance but early foetal mortality, which increased with ovulation rate, tended to upset it. The mean number of foetal cotyledons per foetus depended on litter size and distribution, and at any fixed litter size was substantially reduced in those ewes with six or more ovulations. Foetal weights were also relatively low in these ewes. The total weight of cotyledons per foetus decreased by about 12% for each increase of one in number of foetuses, as compared with a 20% decrease in number of cotyledons but only a 7 to 11 % decrease in the weight of the individual foetuses. Comparisons between foetuses within the same litter led to similar trends in the ratios of cotyledon numbers, cotyledon weights and foetal weights. It is suggested that the presence of some very small lambs in large litters should not be attributed to maternal under-nutrition in late pregnancy.

Breeding and gestation facilities for swine. Matching biology to facility design

The rate-limiting phase of commercial swine production is breeding. The design of the breeding/gestation facilities influences the capacity of the producer to efficiently manage the breeding stock around the time of service and during the postservice period. Thus, breeding design potentially affects total born litter size and farrowing rates. In general, with original construction and facility renovation, the three principal activities of the breeding/gestation phase of production, (1) boar exposure/estrus detection, (2) breeding, and (3) gestation and pregnancy detection, should be independently considered.

Prostaglandins in swine reproduction

A review is presented of the roles of prostaglandins in swine reproduction. PGE and PGF are both produced in the ovary. PGE is thought to mediate steroidogenic activity of L.H. on the development of the granulosa cells leading to increased progesterone production in the preovulatory phase of the oestrus cycle. PGF2 acts on the theca cells leading to increased oestradiol and oestrus manifestation. The PG blocker indomethacin prevents oocyte rupture, but not maturation. The L.H. surges in the follicular phase stimulate ovarian PG production which initiates oestrus and ovulation. The uterus produces PGF2alpha. Disorders leading to abortion usually result in excess PGF2alpha production at the endometrium leading to luteolysis. With normal gestation circulatory progesterone levels fall during the last two weeks of pregnancy associated with increased circulatory foetal corticoid levels. The foetal corticoids are thought to trigger endometrial PGF2alpha levels leading to luteolysis and parturition. The use of exogenous PGF2alpha for induction of oestrus and abortion, parturition, semen collection and resolution of anoestrus is reviewed.