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Title: INCREASING THE HOLDING TIME AT 15 C OF BOAR SPERMATOZOA BEFORE FREEZING DECREASES FERTILITY AFTER THAWING.

Author
item Guthrie, Howard
item Welch, Glenn

Submitted to: Journal of Animal Science Supplement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2003
Publication Date: 6/1/2003
Citation: Guthrie, H.D., Welch, G.R. 2003. Increasing the holding time at 15 c of boar spermatozoa before freezing decreases fertility after thawing. [abstract]. Journal of Animal Science. 81(2):88.

Interpretive Summary: In order to meet special needs of swine producers and the National Animal Germplasm Program (NAGP)preservation of genetic diversity for boar spermatozoa, boar semen is shipped from the site of collection to a laboratory where it is cryopreserved. The purpose of this experiment was to determine if freezing boar sperm on the day following collection (24 hour holding period) would be detrimental to sperm viability and fertility compared to freezing after a 3 hour holding period on the day of collection. Boar semen was diluted in different two commercial boar semen extenders and held for either 3 or 24 h at 15 C to simulate overnight shipment, and then frozen. Thawed spermatozoa were used for artificial insemination (AI) of female swine. The pregnancy rate 23 days after AI favored the 3 h compared to the 24 h holding time, 75 and 53%, respectively; but the difference was not significant. However, embryo number per animal and embryo survival percentage were decreased from 15 to 9 (p = 0.0305) and from 73 and 46% (p = 0.0015), respectively, as holding time at 15 C increased from 3 to 24 h. Pre-freeze and post-thaw sperm viability was not greatly affected by holding time and was of little value in predicting sperm fertility at different holding times. These results are important to swine producers and the NAGP because they indicate that fertility of thawed sperm will be reduced after overnight shipping of liquid semen to another location before cryopreservation, under conditions in which sperm would be expected to remain fertile in liquid form.

Technical Abstract: An experiment was conducted to determine the effect of pre-freeze holding time and commercial extender type on boar spermatozoa viability and fertility. One ejaculate from each of six boars was held in two commercial boar semen extenders, Beltsville Thawing Solution and Androhep Plus, for either 3 or 24 h at 15 C to simulate overnight shipment, and then frozen in 0.5- and 5-mL straws. The spermatozoa thawed from the 5-mL straws were used for artificial insemination (AI) of 31 gilts and sows within 4 h before the expected time of ovulation induced by injection of 750 IU of hCG 130 h after the last feeding of Regu-Mate for estrus synchronization. The pregnancy rate 23 days after AI favored the 3 h compared to the 24 h holding time, 75 and 53%, respectively; but the difference was not significant. However, embryo number per animal and embryo survival percentage were decreased from 15 to 9 (p = 0.0305) and from 73 and 46% (p = 0.0015), respectively, as holding time at 15 C increased from 3 to 24 h. Pre-freeze and post-thaw sperm motility, plasma membrane integrity, and acrosome morphology were of little value in predicting the decrease in sperm fertility after increasing holding time from 3 to 24 h. These results are important because they indicate that fertility of thawed sperm will be reduced after overnight shipping of liquid semen to another location before cryopreservation, under conditions in which sperm would be expected to remain fertile in liquid form.