Influence of Adjusting Timing and Frequency of Mating on the Anticipated Duration of Estrus on Reproductive Performance of Sows

North Carolina State University Swine Reproduction Research from 1998-2000. Recent work conducted by Kemp and Soede (1996) has provided a comprehensive evaluation of the relationship among the duration of estrus, ovulation, timing of inseminations and fertility. In this study, ovulation was monitored via real-time ultrasonography allowing for a precise estimation of its occurrence. Data from this study demonstrate three important relationships. Firstly, the duration of estrus was inversely related to the weaning-to-estrous interval. In other words, sows that exhibit estrus within a short time period after weaning are sexually receptive for longer periods of times than their counterparts which have extended weaning-to-estrous intervals. Secondly, although the length of estrus varied among animals, ovulation consistently occurred at 71% of the duration of estrous. Sows exhibiting estrus for 48 and 72 hours ovulated at 34 and 51 hours, respectively. And finally, if matings occurred between 0 and 24 hours prior to ovulation, then fertilization rates were greater than 90%. These results are exciting and have important implications for development of mating regimens. The inverse relationship between the length of estrus and the weaning- to-estrus interval may provide a way to further refine the optimal mating regimen for sows on an individual basis. Obviously, the length of estrus can only be obtained retrospectively after breeding decisions are made. However, if the weaning-to-estrous interval is known before breeding is initiated, then it may provide a means to assign sows to breeding regimens. The objective of this study was to determine the effectiveness of using the weaning-to-estrus interval as a means of adjusting both the timing and frequency of matings for sows.