Variability in ejaculation rate and libido of boars during reproductive exploitation
The main objective of the study was to evaluate variability in the ejaculation rate and libido of boars under various genetic and non-genetic influences. A total of 7171 semen samples were collected from Swedish Landrace, Large White and Duroc boars reared under commercial production conditions. Time spent in preparing or collecting, constituted the period from the entry of boars into the room for collecting semen to onset of ejaculation. Ejaculation rate was defined as the volume of sperm extracted (mL) per unit of time (min). The index of boar libido was defined as the relationship between productive (duration of ejaculation) and unproductive (time spent in preparing to collect/jump) periods. Average values of the interval between two collections, age of boar at collection, time spent in preparing for collection, duration of ejaculation, volume of ejaculate, rate of ejaculation and libido index were: 8.83 days, 551.2 days, 3.56 min, 6.06 min, 231.9 mL, 37.67 mL/min and 1.76, respectively. Ejaculate traits and libido varied according to breed, season and collector, with the exception of seasonal variability of duration of ejaculation. The regression effect of the interval between two collections of ejaculate and age of boar at collection was not statistically significant only for duration of preparing for collection. Unlike the ejaculation rate, during the summer and autumn periods, boars exhibited weaker libido than in winter and spring. Duroc boars were inferior to the fertile breeds (Swedish Landrace and Large White) in terms of shorter duration of ejaculation, lower volume, lowest rate of ejaculation and weakest libido. Variability of rate of ejaculation and of boar libido indicates the need to include these traits in breeding programmes and the possibility of improving these traits.
Keywords: Breed, ejaculate, libido index, pig, season, swine, variability