Genetic variation in head morphometry of rabbit sperm

The aim of this study was to determine the repeatability and heritability of sperm head characteristics: width (W, μm), area (A, μm2), length (L, μm), and perimeter (P, μm), and to explore the relationships between them and with the selection objective in a rabbit paternal line selected for daily weight gain (DG, g/day) between 28 and 63 days of age. Six sets of three-trait analyses were performed involving 12,908 DG records, with 1795 ejaculates corresponding to 283 males and 14,700 animals in pedigree file. The results obtained showed that sperm head dimensions are heritable (ranged between 0.2 and 0.29). The genetic correlations between sperm traits were always high and positive (between 0.72 and 0.90), with the exception of L-W genetic correlation, which was moderate. Regarding the genetic correlations between DG and sperm head characteristics, the resulting means ranged from −0.09 for L-DG to −0.43 for W-DG, showing a consistent evidence of the negativity of the genetic correlations. Further studies should be focused on the relationship between sperm head morphometry and different semen or ejaculate characteristics and also between sperm head morphometry and field fertility and prolificacy.