Selection for sperm quality in White Plymouth rocks.

A selection for sperm quality was carried out in the White Plymouth Rock population of the Spelderholt institute. The percentage of morphologically abnormal spermatozoa was used as the most important selection criterion. The population was selected in two directions, viz. a line with a low incidence (Ll-line) of abnormal spermatozoa and a line with a high incidence (Hl-line). Cocks were examined and selected at the age of 26 weeks with the help of vital stained sperm smears. The selection response in the Ll-line appeared to be very evident; in the Hl-line the results were more variable. An indirect effect of selection on 8-week bodyweight could be established.