Diluents for Bovine Semen. XI. Effect of Glycerol on Fertility and Motility of Spermatozoa in Homogenized Milk and Skimmilk

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Abstract
When 10% or 13% glycerol was incorporated in skimmilk diluent by gradual addition to partially diluted semen at 5[degree]C, spermatozoan livability during 14 days of storage at 5[degree]C was higher (P< 0.01) than in the absence of glycerol. These glycerol levels prevented the sharp decline in motility observed between the 4th and 6th days of storage for semen diluted in skimmilk without glycerol. Glycerol levels of 16 to 25% did not significantly improve livability over semen diluted without glycerol. Four field trials involving 21,676 inseminations were conducted to compare the fertility of semen diluted in milk with that diluted in milk-10% glycerol. Homogenized milk was used in 2 trials and fresh, unfortified skimmilk in the other 2. The combined data showed that addition of glycerol significantly (P<0.01) increased fertility of semen used the 2nd, 3rd, and 4th days after the day of collection by 7.4, 12.2, and 19.5 percentage units, respectively. The increase of 2.3 percentage units obtained with glycerolated semen used the day after collection was not significant. In a limited split-ejaculate trial, fertility of semen diluted in homogenized milk containing 15% glycerol was not significantly different than that in 10% glycerol on any of the 3 days of use.