The influence of six generations of selection for fertility of frozen-thawed semen in the fowl on fertility, semen characteristics and semen cholesterol and phospholipid levels

The influence of 4, 5 and 6 generations of selection for duration of fertility of frozen-thawed chicken semen on fertility and hatchability of frozen-thawed semen, fertility of fresh semen, semen volume, concentration of spermatozoa, spermatozoal motility and on spermatozoa and seminal plasma cholesterol and phospholipid levels and their ratios (generations 5 and 6) as well as the genetic influence on these traits was studied. A selected line and an unselected control line of broiler chickens were used.All estimates of fertility of frozen-thawed and fresh semen were significantly (P 0.05).The heritabilities of fertility of frozen-thawed and fresh semen and semen characteristics were generally low and those for spermatozoa lipid levels and their ratios were generally medium.The positive phenotypic correlations between estimates of fertility within frozen-thawed and fresh semen were high but low between fertility of frozen-thawed and fresh semen. The phenotypic correlations between semen characteristics and fertility were inconsistent. The phenotypic correlations of spermatozoa and seminal plasma cholesterol with fertility of frozen-thawed semen were negative as were the phenotypic correlations of seminal plasma cholesterol with fertility of fresh semen. Genetic correlations were also calculated and were similar in direction to the phenotypic correlations but their magnitudes exceeded unity in many cases. The level of inbreeding was uncorrelated with either fertility, semen characteristics, spermatozoa and seminal plasma lipids or their ratios