NUMBER OF ARTIFICIAL INSEMINATIONS PER ESTRUS IN SWINE: ASSOCIATION WITH ESTRUS PROFILES AND IMPACT ON REPRODUCTIVE PERFORMANCE

Abstract

In swine, multiple artificial inseminations (AI) are commonly performed per estrus due to the long estrus duration. This observational study aimed to evaluate the association among the number of AI conducted per estrus, the estrus duration and the subsequent reproductive performance on a commercial swine farm. After evaluation of both estrus profile and follicle dynamics using ultrasound, by two independent teams, the number of AI per estrus was recorded, with no interference in the farm habitual management. The first AI was done at the time of estrus detection and subsequent AIs were done at 12 h intervals, as long as females showed estrus signs. The risk of conducting more than three AI per estrus as a function of estrus duration was also estimated. For females receiving two AI per estrus, farrowing rate (92.0%) was higher (p < 0.05) than for those receiving three (77.5%) or four to six AI (79.6%). Total litter size did not differ (p > 0.05) for females receiving two, three or 4 to 6 AI per estrus (10.6, 12.0 and 12.0, respectively). For females having estrus longer than 78 horas, the odds of receiving 4-6 AI were 6.1 times higher than for those having estrus shorter than 50 hours, and 3.4 times higher than for those having estrus within 50 to 74 h (both p < 0.05). Thus, although long estrus duration allows multiple AI per estrus, we concluded that more than three AIs per estrus are not recommended because there is no benefit for subsequent reproductive performance.

Keywords: Estrus duration, farrowing rate, litter size, swine.