The effect of age, interval collection and season on selected semen parameters and prediction of AI boars productivity

The possibility of planning the production level has a special importance for AI stations, and its inaccuracy should be minimized by eliminating the factors differentiating the quantity and quality of the ejaculate. The aim of the study was to determine the effect of age, collection interval and season on selected quantitative and qualitative semen parameters and to develop equations for estimating production capacity for AI stations. The study included 48 117 ejaculates. Experimental groups were created according to: age of boar (8-9, 10-12, 13-18, 19-24, 25-30, >30 months), collection interval (≤2, 3, 4, 5, 6, 7, ≥8 days), and season (Winter, Spring, Summer, Autumn). Selected quantitative and qualitative parameters were analyzed: semen volume (ml), spermatozoa concentration (×106 ml−1), total number of spermatozoa in ejaculate (×109), number of motile spermatozoa in ejaculate (×109), and number of insemination doses obtained from one ejaculate (n). The most important role in shaping the results was played by interactions. The highest semen volumes were achieved for the oldest boars after 7-day interval collection during Autumn (about 300 ml). Interestingly, the lowest semen volumes were also noted during Autumn from the youngest boars after 1-2 and 7-day interval collection (a little over 160 ml). The highest spermatozoa concentrations (515×106 ml−1) were observed in Autumn for 10-12 month-old boars with the longest interval collection, which clearly demonstrates the positive impact of long resting on young boars. The lowest spermatozoa concentrations - below 300×106 ml−1 - were reported for the oldest boars after 1-2 and 3-day collection intervals. The highest total number of spermatozoa in ejaculate and motile spermatozoa were noted during the longest collection interval in Winter at the ages of 13-18 months and 25-30 months, while the lowest occurred in the same season with a short interval from the 10-12 month boars. Almost all correlations were statistically proven at the level of P≤0.05 and P≤0.01, except for the correlation between the number of motile spermatozoa and the age of boars. Developed regression equations enable, with a high degree of accuracy, the estimation of the selected ejaculate parameters on the basis of age, collection interval and season. The solution proposed in the article is a useful tool, especially for AI stations or large farms with a high rate of boars producing semen for AI. AI stations assessing the long-term production capacity of boars should take into account the factors examined in this study. Underestimation of the interaction may, in fact, reduce the number of insemination doses by up to 5 portions of a single ejaculate.