The effect of resting roosters from ejaculation on the quality of spermatozoa in semen.

Abstract

During an investigation of the chemical composition of fowl semen it was felt necessary to study the effect of varying the length of rest periods between ejaculations on the quality of fowl spermatozoa. Such information could be useful for future work on the storage of semen in vitro for long periods, since there might be an optimum ejaculation rate for obtaining spermatozoa of the best quality and thus likely to survive best in vitro. Twenty related males of the Breeding Line of Brown Leghorns at the Poultry Research Centre, Edinburgh (Blyth, 1954) were selected randomly from roosters trained for the artificial collection of semen. Semen had been collected and examined at least once weekly from all the males for a month before the start of the experiment. The males were subdivided randomly into five groups; one group was kept as a control and the other four were rested for 2, 4, 6 and 8 weeks respectively, between ejaculations. Semen was collected consistently from the males in the control group throughout a 10-week experimental period at intervals of 2, 3 or 7 days; each time the morphology of spermatozoa in semen samples was examined in nigrosin-eosin smears (see below). Semen was taken from the four groups of experimental roosters at the end of their allotted rest periods and examined; thereafter semen was collected as frequently as in the controls and during the 9th and 10th weeks was examined once again. A nigrosin-eosin stain technique was used to examine the quality of spermatozoa in smears of semen samples. Nigrosin (0\m=.\6g) was added, with constant stirring at room temperature, to 10 ml isotonic glutamate solution (Lake, 1960) containing 0\m=.\16 g eosin. Aliquots of 0\m=.\50ml of this stain mixture were put into small test-tubes kept in ice-cold water. Clean uncontaminated semen was collected and 0\m=.\02ml added to the stain and mixed thoroughly. After 10 min one drop of the stain-semen mixture was placed on a clean slide and a smear made. The slide was dried quickly and thoroughly in warm air and the smear mounted with DPX (Gurr Ltd) mounting fluid and a coverslip. Duplicate