The fertility of Merino ewes artificially inseminated with semen diluted in solutions based on skim milk, glucose or ribose

Abstract

The fertility of Merino ewes artificially inseminated with semen diluted tenfold in milk or buffered glucose solution was lower than that of a control group of ewes inseminated with the same number of spermatozoa in undiluted semen. By means of centrifugation, the concentration of spermatozoa in the insemination dose of diluted semen was raised to match that of the undiluted semen and then the effect of dilution on fertility was eliminated for the glucose-diluted semen, but not for the milk-diluted semen. Respective percentages of ewes not returning to oestrus and ewes lambing were, after insemination with undiluted semen, 60.5, 46.7; with milk-diluted semen, 55.9, 40.2 and after reconcentration 56.0, 38.0; with glucose-diluted semen, 48.2, 35.3, and after reconcentration 62.1, 46.1.

In another experiment, the percentage of ewes lambing after insemination with undiluted semen, with semen diluted tenfold with glucose, and with semen diluted with a ribose mixture and chilled at 5°C for 24 hr were respectively 67.0, 58.0, and 26.1. Both diluents contained 6% (v/v) egg yolk and diluted semen samples were reconcentrated to the original sperm density of the semen immediately before insemination.