Effects of induced endometritis on the life-span of corpora lutea in pseudopregnant rabbits and incidence of spontaneous uterine infections related to fertility of breeding does

摘要

The hypothesis that uterine infections induced by the insemination procedure are related to delayed luteolysis and high progesterone concentrations present at the time of AI was tested. Nulliparous mature New Zealand White female rabbits (3 per group) were given 0.8μg GnRH analogue (Receptal; day 0) just prior to infusing the uterus with sterile extender (control group) or with extender inoculated with 0.5, 1 or 2 X 106 Pasteurella multocida (treated groups). The functional lifespan of CL was assessed by evaluating plasma progesterone concentrations from days 0 to 23 of pseudopregnancy. In treated rabbits, the progesterone profiles closely overlapped those in controls until approximately day 14. Thereafter, they varied markedly between animals, but luteolysis was delayed by at least 5-6 days and developed less rapidly than in controls. On day 21, progesterone concentrations were higher than normal in 4 treated does. In a field survey, vaginal swabs were collected at the time of the second AI from 114 non-pregnant rabbits and those positive to bacteriological culture, were killed 16 days later to collect uterine swabs. 19 of 34 does with a positive vaginal swab had positive uterine swabs and were not pregnant. The most frequent pathogen isolatedwas Staphylococcus aureus (50%), followed by Escherichia coli (37.5%) and P. multocida (12.5%). It is concluded that uterine infection increases the lifespan of CL in non-pregnant does, and that infections of the genital tract are quite common among does on breeding farms, probably related to using AI.