Heterosis for morphometric characteristics of sperm cells from Duroc x Pietrain crossbred boars.

Morphometric studies of spermatozoa were conducted on 30 ejaculates collected from 15 boars represented by five Duroc boars, five Pietrain boars and five Duroc x Pietrain crossbred boars. Spermatozoa were stained using two methods: eosin-nigrosin and eosin-gentian. Values for morphometric measurements of sperm cells including head length, head width, head area, head perimeter, tail length and total sperm cell length were collected, and indices characterizing sperm cell morphological structure were calculated. The effects of heterosis on dimensions and shape of sperm cells from Duroc x Pietrain boars were evaluated. The effects of genetic effects on sperm head dimensions and shape were determined. Duroc x Pietrain crossbred boars produced spermatozoa with larger heads than purebred Duroc and Pietrain boars. The heads of sperm cells from crossbred boars were more rounded in shape, whereas sperm heads from purebred boars were more elongated. There were marked effects of heterosis on sperm head size and shape. Spermatozoa from Duroc boars also had larger and more rounded heads and longer tails than sperm cells from Pietrain boars. In addition, staining method affected the outcome from evaluation of heterosis on dimensions and shape of sperm cells. There were larger heterotic effects based on morphometric measurements of heads of spermatozoa stained using the eosin-nigrosin method than with use of the eosin-gentian dye technique.