Effects of Altrenogest and Exogenous Gonadotropins on Ovarian Function and Embryo Recovery in Swine Leukocyte Antigen Inbred Miniature Swine as Influenced by Cystic Endometrial Hyperplasia12

Altrenogest (ALT), a synthetic progestogen, and exogenous gonadotropins were administered to the Swine Leukocyte Antigen (SLA) inbred miniature pig that typically has a reduced ovulation rate and small litter size. In Study 1, 15 adult female pigs were either controls (Group I, n=5), fed 15 mg ALT/day for 14 days (Group II, n=5), or fed ALT and treated with pregnant mare’s serum gonadotropin (1200 IU, i.m.) and human chorionic gonadotropin (500 IU, i.m.) 24 h and 104 h, respectively, after ALT withdrawal (Group III, n=5). In Study 2, tbree groups of pigs (I, n=24; II, n=11; III, n=11) were treated similarly to those in Study 1 except that pigs in Study 2 (Groups II and III) were mated. Ovaries of all animals in both studies were examined laparoscopically or by laparotomy 5–8 days after estrus to assess ovarian activity. The uteri of Group II and III animals in Study 2 were flushed with tissue culture medium, which was evaluated for the presence and quality of embryos. No pig demonstrated estrous behavior during ALT administration. Not all animals demonstrated typical estrous behavior after ALT withdrawal. When the data from both studies were combined, 2 of 16 (12.5%) of group II and 6 of 16 (37.5%) of Group III pigs failed to demonstrate standing estrus. Following ALT with-drawal, females in Groups II and III returned to estrus in 5.6 ± 0.3 and 5.8 ± 0.3 days, respectively (p>0.05). Corpora lutea number was increased (p<0.05) by ALT treatment alone (11.4 ± 1.8) compared to controls (6.9 ± 1.3) and was increased (p<0.01) further by the use of exogenous gonadotropins (22.6 ± 1.9). Normal-appearing morula and blastocysts were recovered from 14 of 22 females. However, cysts were found in the endometrium of 5 of 9 and 9 of 10 pigs in Groups II and III, respectively. The extent of this condition, classified histologically as cystic endometrial hyperplasia (CEH), varied among females, and its occurrence appeared age-dependent. Subsequent evaluation of untreated SLA miniature pig herd-mates revealed that CEH was unrelated to ALT orgonadotropin treatment. This study demonstrates that ALT treatment alone is effective in synchronizing estrus and has a beneficial influence on ovulatory response in the SLA miniature pig. The supplemental use of exogenous gonadotropins stimulates further ovulatory response; however, the incidence and intensity of overt estrous behavior is reduced. Recovery of morphologically normal embryos suggests that fertilization is unaffected. However, small litter size at term may be associated with cystic degeneration of the uterine endometrium, which could result in increased embryonic mortality and/or a reduced rate of implantation.