Abstract
BackgroundPseudomonas aeruginosa may cause venereal disease and infertility in horses. A Pseudomonas aeruginosa - carrier stallion, often unresponsive to artificial vagina collection, was used to naturally breed mares. Semen collected from the same stallion was also used to perform artificial inseminations. Pregnancy rates, embryo quality and incidence of uterine infection were compared between inseminated or naturally-bred mares.MethodsP. aeruginosa was isolated from swabbing of the penis, prepuce and distal urethra of the stallion. Before being bred or inseminated, clitoral/vestibular samples were collected from all mares, and cultured for isolation of P. aeruginosa. At the first observed estrus, endometrial swabs were also collected. All mares subjected to natural mating (NS) were re-evaluated for P.aeruginosa by culture of clitoral and endometrial swabs. Artificial inseminations (AI) were performed either with fresh-extended semen (11 AI/7 mares) or frozen semen (10 AI/7 mares). The stallion was also used to breed 3 mares (4 services). For embryo collection, 2 mares were inseminated with fresh-extended semen (1 AI/mare), and 2 additional mares were inseminated with frozen semen (2 AI/mare). Two mares were naturally-bred with a total of 9 services, for embryo collection. All mares were examined after AI or natural service (NS), for uterine pathologies. Embryo recoveries were attempted passing a catheter with inflatable cuff connected to a sterile flexible 2-way flushing catheter, through the cervix. Flushed media was recovered into an Em-Con filter, and embryos searched using a stereoscope. Embryos were graded from 1 (excellent) to 4 (degenerated/dead).ResultsPregnancy rates obtained after NS was 50% per cycle. However, more than half of the NS resulted in uterine disease, while uterine pathology was seen only in 22% of the time following AI. Half of the mares bred by NS got positive to P. aeruginosa. Percentage of embryo recovery rates was identical after AI or NS (66.7%). The 4 embryos recovered after AI were classified as Grade 1, while after NS only 2 out of the 6 recovered embryos were Grade 1.Conclusiona) there was no evidence of reduced fertilization after AI or NS, b) a numerically higher incidence of uterine disease was noticed after NS, c) venereal transmission of P. aeruginosa after NS was confirmed, d) a lower percentage of G1 embryos may be obtained after NS. Overall, the data supports the indication for P. aeruginosa-carrier stallions to be bred by AI rather than by NS, and raises the possibility that P. aeruginosa may affect embryo quality.
Highlights
Pseudomonas aeruginosa may cause venereal disease and infertility in horses
In the present work we decribe the conception rates obtained after natural service (NS) with a stallion carrier of P. aeruginosa, the conception rates after artificial insemination (AI) with fresh extended and frozen/thawed semen of the same stallion, the incidence of uterine disease with either method of breeding, as well as embryo recovery rates and embryo quality after AI and NS
Pregnancy rates as well as embryo recovery rates obtained after NS with the infected stallion were acceptable despite having more than half of the NS resulting in uterine disease compared to only in 22% following insemination
Summary
A Pseudomonas aeruginosa - carrier stallion, often unresponsive to artificial vagina collection, was used to naturally breed mares. P. aeruginosa can cause venereal disease and infertility in the equine [3,4] and it is generally accepted that stallions contaminated with this bacteria need to be considered potential carriers of a venereal-transmitted disease [5], in particular when used to breed older mares [2]. Artificial insemination (AI) associated with minimum contamination techniques is considered to have a distinct advantage over natural service to control the transmission of these bacteria [3]. The effect of those techniques on the control of the disease and even the rate of transmission by infected stallions after natural service (NS) is poorly documented and the effect of NS by P. aeruginosa-carrier stallions in embryo quality have not been reported. In the present work we decribe the conception rates obtained after NS with a stallion carrier of P. aeruginosa, the conception rates after AI with fresh extended and frozen/thawed semen of the same stallion, the incidence of uterine disease with either method of breeding, as well as embryo recovery rates and embryo quality after AI and NS
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