Authors : K.V. Kousenidis , E.A. Kipriotis and G. Maglaras
Abstract: The seasonal subfertility syndrome was studied on the basis of determining whether the elevated numbers of Services induced by sows returning to estrus have an impact on the numbers of sows impregnated in the reduced fertility period of July-August-September. Numbers of sows mated (Services) and sows that farrowed (Pregnancies) were collected from 5 pig farms located in three different regions of mainland Greece. A total of 2303 sows were involved in 6809 matings and 5606 farrowings grouped in monthly observations over a period of 12 months. The collected data was analyzed in respect of the Services-Pregnancies relation and the potential effect of farm and season on this relation. The thorough statistical analysis provided the proof for a close, non-linear relation between Services and Pregnancies (R2 = 0.96, p<0.01). There was no farm effect established on the Services-Pregnancies relation. The effect of a season-specific factor was found to generate an inverse relation between pregnancies and services in the months of July, August and September (R2 = 0.97, p<0.01) suggesting that the increased amount of services potentially consists of one of the factors that explain the decreased pregnancy levels. Excessive numbers of Services were then shown unable to relate to numbers of Pregnancies when the season-specific factor was ignored. It was therefore, concluded that elevated numbers of Services, which are, themselves, caused by unsuccessful matings of sows returning to estrus in the period of July-August-September, enhance the expression of reduced fertility and constitute an element of the seasonal subfertility syndrome.
K.V. Kousenidis , E.A. Kipriotis and G. Maglaras , 2009. Seasonal Subfertility in Pigs: The Effect of Elevated Service Numbers on the Expression of the Syndrome. Journal of Animal and Veterinary Advances, 8: 255-264.