Effects of the number of spermatozoa and volume of diluted semen on fertility in the ewe

Abstract

Incidence of pregnancy in artificially inseminated Merino ewes was not significantly affected by dilution of semen with buffered glucose so as to present equal numbers of spermatozoa in different volumes (50 or 200 µI) or by reducing number of spermatozoa per insemination from 100 to 50 million. Respective pregnancy percentages for various volumes and concentrations of semen were: 50 µl, 50 x l06, 48.7%; 200 µl, 50 x l0⁶, 57.1%; 50 µl,100 x l0⁶, 53.8%; 200 µl , 100 x 10⁶ 52.9%; 31 µl, 100 x l0⁶ (undiluted control), 60.2%.

The percentage of pregnancies was significantly higher among ewes with clear or heavy (v. light) raddle marks left by the teaser rams used to detect oestrus, and among those with a copious flow of vaginal mucus at insemination. The fertility of all semen fell as the interval between collection and insemination increased to 1 hr.