Number Of Placentomes Research Articles

Maternal reproduction and health in the Grant's gazelle (Gazella granti)

This study attempts to identify influences contributing to maternal and neonatal insufficiency with reference to the high neonatal and calf mortality common to wild tropical ungulates. Fiftyfour post‐pubertal female Grant's gazelle (Guzellu grunti) were collected and autopsied in northern Tanzania, East Africa. Ovulation was equal between right and left ovaries, but 81.25 % of corporu luteu were on the left, while implantation had a preference for the right of 83 %. The corpus luteurn is transient, regressing after the foetus has attained about I % of its weight at term. The gross uterine changes suggest a highly efficient animal, producing a dispro‐ portionately large foetus for maternal size, with a high number of placentomes of efficient design. Uterine fluids decline from 57.1 % of total uterine weight at about 50 % of gestation time, to 11 at 95 % of gestation time. Foetal growth rate was similar to that of other investigated bovids, but the near‐term foetus represented 70–80 % of the total uterine weight compared to the 60 % proposed as normal by other workers. Lactation ceased when foetal weight was an estimated 5.4 to 7.5 months. Weight of the mammary gland was positively correlated with the percentage intake of graze, and the gland apparently produced more milk in the wet season. The adrenal glands of non‐pregnant animals were significantly large, and this was attributed to lactational stress. Blood RBC, Hb, PCV and WBC values compared with average values given by other workers, and with those for sheep and goats. Reference is made to the apparent occurrence of fatty livers related to lactational stress. Gluconeogenesis offered no clues in the small samples investigated as to its role in neonatal survival. Rumen fill was 17.8 % lower in animals with foetuses > 3000 g. Maternal kidney and omentum fat deposits appeared influenced both by food availability and by the reproductive cycle. Body weight also was significantly heavier in the dry season, and highest in animals with foetuses > 3000 g. Dates of conception and birth were calculated from foetal brain weight as well as body weight and crown‐rump length, and the mean of the three predictors taken. This gave peak births in June, at the onset of the dry season when food requirements of lactation are sub‐optimal in availability; and the survival of calves suggests a high mortality in the first 1–2 months after birth. But the species appears better adapted to a dry environment, and the inference drawn is that graze is of less value than browse in maintaining maternal fitness, but is of greater importance to lactation.

SOME EFFECTS ON THE CONCEPTUS OF PRIOR IMMUNOLOGICAL SENSITIZATION OF EWES TO THE SIRE

Summary. One half of the forty-eight New Zealand Romney ewes to be mated with either a Romney or Southdown ram were immunologically sensitized to the ram 2 weeks before tupping. After 12 to 13 weeks of pregnancy, the ewes were slaughtered and each reproductive tract and conceptus examined. Sensitization to the sire had no effect on fecundity, fertility, placental weight or foetal size. However, the number of placentomes per foetus tended to be larger in sensitized than in control ewes and was significantly greater in inter-breed than in intra-breed matings. It is suggested that the increased number of placentomes is due to heightened sensitivity of the maternal and foetal tissues at implantation, resulting from their antigenic differences.