Improved Fertilization Success Using Laparoscopic Oviductal Artificial Insemination with Low Sperm Numbers in Domestic Cats.

Abstract

Artificial insemination (AI) is a valuable tool for infusing genetic variation into stagnant populations, especially using frozen-thawed spermatozoa, and for propagating physically or behaviorally incompatible individuals. Within zoological institutions, AI has received growing interest for genetic management of endangered felids, provided that AI success can be optimized for applied usage. Traditionally, laparoscopic AI in cats involves treatment with equine chorionic gonadotropin (eCG) followed 80-85h later by human CG (hCG) to induce follicular development and ovulation, with subsequent bilateral sperm deposition into the uterine lumen. However, hCG, a large glycoprotein, may remain in circulation for several days post-injection, generating undesirable secondary ovulations. Uterine AI also requires relatively high numbers of spermatozoa to achieve sperm transport through the uterotubal junction and fertilization within the oviduct. Furthermore, sperm recovery from male cats frequently is poor, limiting the number of spermatozoa available for AI. Alterations in the AI protocol, using short-acting porcine luteinizing hormone (pLH) as the ovulatory signal and oviductal AI for sperm deposition, could improve fertilization success while requiring fewer spermatozoa. Our objectives in this study were to assess pregnancy and fertilization success in cats treated with one of two gonadotropin regimens (eCG/hCG vs. eCG/pLH) and inseminated laparoscopically at two sperm deposition sites, the uterus (UT) and the contralateral oviduct (OV). Sixteen female domestic cats were randomly assigned to either eCG (100 IU)/hCG (75 IU) or eCG/pLH (1000 IU) treatment groups. All 16 females ovulated following gonadotropin treatment and were inseminated with low sperm numbers (1x106 motile sperm/site; 5 µl volume) in one uterine horn and one contralateral oviduct using freshly collected semen from a different male for each site. Semen samples were obtained from two males of proven fertility via artificial vagina. Pregnant females were spayed at 20-21 days post-AI and recovered fetuses assessed for paternity using genetic analysis. Comparing gonadotropin regimens, similar numbers of females became pregnant following eCG/hCG (75%, 6/8) versus eCG/pLH (63%, 5/8). The number of corpora lutea (CL) at AI was similar between regimens, but hCG treatment increased the number of CLs at day 20 post-AI. Although hCG and pLH treatments produced similar numbers of normal fetuses, implantation abnormalities (e.g. empty gestational sacs, malformed placentae) were observed in the hCG, but not pLH, group. Overall, 11 (of 16; 69%) females became pregnant (5 cats from OV AI only, 2 from UT AI only, and 4 from both sites). In comparing insemination sites, more fetuses resulted from OV AI (36/49; 73%) than UT AI (13/49; 27%). To assess capacity for term pregnancies, three additional females were treated with eCG/pLH and inseminated in one oviduct and the contralateral uterine horn. All three females became pregnant (2-3 fetuses each) and healthy kittens were produced. In summary, laparoscopic oviductal AI with low sperm numbers in eCG/pLH-treated females resulted in high pregnancy and fertilization percentages in domestic cats. These findings suggest that this technique may have value for propagating endangered nondomestic cat species. Our recent success in using oviductal AI in eCG/pLH-treated ocelots (Leopardus pardalis) to produce a healthy ocelot kitten supports this cross-species applicability. (platform)