Osborne Selection Index and Semen Traits Interrelationships In Rhode Island Red and White Breeder Cocks

Abstract

Three hundred and sixty-one cocks from five hatches, one week apart, were used in this study. The birds which were made up of 203 birds from strain A (male line) and 158 birds from strain B (female line) were subjected to semen collection using the massage technique. The ejaculates were then subjected to both physical and chemical evaluations for semen quality analysis. The parameters considered were semen volume, semen colour, sperm progressive motility, sperm concentration, total sperm per ejaculate, concentration of live sperm and percent abnormal sperm. Results showed that the mean values for all the parameters lie within the acceptable range reported for normal cock semen. Moderate to high heritability estimates for most of the semen traits were also observed. The least square means (±SE) for semen volume, sperm progressive motility, sperm concentration, total sperm per ejaculate and concentration of live sperm cells obtained in this study were 0.42±0.02 ml, 73.46±2.04%, 1.47±0.15x10⁹/ml, 64.15±5.67x10⁹/ml and 86.45±2.63%. The heritability estimates obtained were 0.55±0.03 for semen colour, 0.45±0.08 for semen volume, 0.83±0.04 for sperm progressive motility, 0.52±0.06 for sperm concentration, 0.33±0.02 for total sperm count, 0.46±0.03 for concentration of live sperm cells respectively. High and positive genetic correlations between Osborne Selection Index and semen volume, semen colour, sperm concentration as well as with concentration of live spermatozoa were also obtained. The lowest value (0.008±0.010) of phenotypic correlation obtained was for total sperm per ejaculate and the highest value (0.066±0.027) was for semen volume. Therefore the genetic correlation between Osborne Selection Index and most semen traits were positive, hence, selection of males on the index values, currently been practiced in NAPRI, will not bring about any deterioration in semen quality. On the other hand, due to significantly negative genetic correlation between Osborne index and abnormal sperms, it will indirectly improve the semen quality of both lines which in turn may yield better fertility in the Rhode Island flock.