Assessment of the effect of heterosis on semen parameters of two-breed crosses of Duroc, Hampshire and Pietrain boars
The study was performed on 4 609 ejaculates obtained from 32 boars, including 14 purebred and 18 two-breed crosses. The ejaculates were collected manually every 4–5 days. The study involved ejaculates collected from each boar from the first day of its insemination use until the day of semen depletion. Each ejaculate was assessed for the following physical parameters: ejaculate volume, sperm concentration, percentage of spermatozoa with correct motility, total sperm count per ejaculate and number of insemination doses obtained from one ejaculate. The effect of heterosis was calculated on the physical parameters of the boar crosses ejaculates in relation to the mean value of a given parameter for the parent breeds. Positive and well pronounced heterosis effects were identified in the majority of the physical ejaculate parameters of the cross boars for all the cross-breeding variants. A negative effect of heterosis was only identified in the ejaculate sperm concentration of the Hampshire × Pietrain crosses. The highest ejaculatory efficiency was identified in the hybrids produced on the basis of the Hampshire breed. These breeders were also found to feature significant heterosis effects on ejaculate volume, total ejaculate sperm count and number of insemination doses prepared from one ejaculate.