Motility and Fertility during Post-Thawing Storage of Bovine Spermatozoa Frozen Concentrated, Thawed, and Re-Extended

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Abstract
Twenty ejaculates of semen were extended to contain 200 x 106 and 20 x 106 sperm per milliliter in yolk-citrate and whole milk extenders and frozen with 7% glycerol. The semen frozen with 200 x 106 sperm per milliliter was re-extended, after thawing, to 20 x 106 sperm per milliliter in yolk-citrate, whole milk, skim milk, and Cornell Univ. Extender and the motilities of these were estimated during 72 hr. of storage at 5[degree]C. Freezing semen with 200 x 106 sperm per milliliter and re -extending it after thawing in extenders other than those in which the sperm were frozen resulted in improved motilities, particularly as the post-thawing storage interval increased (P< .01). The average fertility for inseminations made from 24 to 60 hr after thawing semen that had been frozen with 200 x 106 sperm per milliliter and re-extended to 15 x 106 motile sperm per milliliter in yolk-citrate and Cornell Univ. Extender was 51.8 and 63.0%, respectively. Inseminations made immediately after thawing control frozen semen averaged 65.5% fertility.