Correlation between objective semen analysis and fertility in Japanese quail

This study investigated the relationship between sperm kinematics and egg fertility in Japanese quail in an attempt to identify a semen trait that could be used to predict male fertility. Males (n=45) and females (n=180) from five strains (A, B, C, D, E) were used. Ejaculates (n=720) were collected from 8 to 38 weeks of male age. Semen volume and sperm concentration were recorded and sperm motility was analyzed using Sperm Class Analyzer (SCA®-CASA). At the time of ejaculate collection, males were allowed to mate with females in order to obtain egg fertility data: percent fertile eggs and the numbers of sperm (SpermOPVL) and sperm-holes (HolesIPVL) present on the egg perivitelline membranes. Sperm concentration was positively correlated with ejaculate volume (r=0.35; P < 0.01) and percent fertile eggs (r=0.08; P < 0.05). There were high correlations (P < 0.01) among the sperm kinematic parameters: percent motile (MOT%), percent rapid (Rapid%), percent progressive (PROG%), percent medium (Medium%), velocity curvilinear (VCL), velocity straight line (VSL), and velocity average path (VAP), linearity (LIN%), straightness of trajecotry (STR%) and beat cross frequency (BCF). The strains differed with respect to the correlations for sperm kinematics and egg fertility: SpermOPVL was correlated (P < 0.05) with VSL (r=0.18), VAP (r=0.18), and BCF (r=0.23) for Strain A, with PROG% (r=0.17) for Strain B, and with Medium% (r=0.18) for Strain C. When the data were adjusted for the effects of strain and age, Medium% was correlated with HolesIPVL (r=0.36; P < 0.01) and percent fertile eggs (r=0.31; P < 0.01), whereas PROG% was correlated with SpermOPVL (r=0.30; P < 0.01) and HolesIPVL (r=0.30; P < 0.01). Males could be ranked into high and low fertility categories based on initial (i.e. Week 8) and the life-time (i.e. Weeks 8-38) data for sperm kinematics and egg fertility. Of the males classified as poorly fertile by Week 8 sperm kinematics, 30% were also confirmed as poor on the basis of life-time sperm kinematics. Of the males classified as poorly fertile by Week 8 egg fertility, 47% were confirmed as poor on the basis of life time-data of egg fertility. We concluded that sperm concentration, Medium%, PROG%, VAP, VSL and BCF are important determinants of egg fertility in quail, and that these relationships depend on genotype.