Influence of season and reproductive management on the morphometry of ram sperm head

Abstract

The aim of the present work was to study the morphometric characteristics of apparently normal ram sperm heads of an ovine insemination centre over a year, using a computer-assisted sperm morphometric assessment system (CASMA) which is commercially available. For this, 383 ejaculates from 9 mature rams kept in non-controlled environmental conditions were used. The morphometry was analyzed in fresh sperm and each spermatozoon was measured for four primary parameters (length, L; area, A; width, W and perimeter, P) and four derived parameters (ellipticity, L/W; rugosity, 4πA/P2; elongation, L−W/L+W and regularity, πLW/4A).A clear seasonal behaviour of both morphometric and derived parameters was observed, with sperm size being larger in autumn and winter. This behaviour was also observed for ellipticity and elongation.Due to organizational reasons in the insemination centre, the rams’ reproductive activity was suspended during the month of August; this fact was reflected, in the ejaculates collected in September, in the decrease of the sperm head size, as well as in the increase of ellipticity.The procedures used in the present study did not allow for natural separation in sperm subpopulations considering the size and shape of apparently normal sperm heads, but it was possible to divide the ejaculate into two subpopulations, taking rugosity into account. These subpopulations were present in all the rams – and had a clear seasonal distribution.