Parity Associated Changes in Reproductive Performance – Physiological Basis or Record Keeping Artifact

North Carolina State University Reproduction Research from 2003. Based on the retrospective analysis of sow herd production records it is evident that reproductive performance tends to increase gradually over the first three to four parities and then begins to decrease as sows reach parity seven or eight. Often, it has been assumed that this initial increase is related to the maturation of some components of the females reproductive system. However, there is little published evidence of parity-based differences in reproductive processes such as estrus, ovulation, fertilization, and prenatal mortality. In addition, the confounding effects of parity (i.e. previous reproductive experience) and age are rarely separated in experiments. Retrospective comparison of the reproductive performance of groups of different parity females almost always ignores the fact that these groups are not comprised entirely of the same individuals. It is quite possible that reproductive performance increases over the first three to four parities because sub-fertile females are gradually removed from the herd. This article attempts to highlight differences in reproductive performance and physiology between gilts, primiparous, and multiparous sows and areas where parity-specific management might be used to increase reproductive efficiency.