A review of the literature indicates that injection of gonadotrophic hormones or giving high-level-energy feeds will markedly increase the number of ovulations in polytocous animals. Higher ovulations rates are then followed by an increase in the precentage of embroys which die in utero. This increased embryonic death may be due either to inherent limitations within the individual embryo or to maternal limitations which affect the litter (Runner, 1951). In any event, the number of young at term reamins at a level characteristic for the species. Empbryonic death usually occurs before the time of attachment of the embryo to the endometrium (Boyd, 1965).
Attempts to increase the number of young born either by hormonal superovulation(Flower & Edwards, 1957; Adams, 1960; Hafez, 1964) or by the addition of embryos to the uterine horns (McLaren & Michine, 1959; Adams, 1960) have seldom been sucessful. In some
If the inline PDF is not rendering correctly, you can download the PDF file here.