Effect of number of motile sperm and number of inseminations using frozen boar semen on fertility in gilts

Authors: SPENCER, KARL - UNIVERSITY OF IL; Purdy, Phil; Blackburn, Harvey; Spiller, Scott; Wilson, Carrie - Welsh; STEWART, TERRY - PURDUE UNIVERSITY; BREEN, S - UNIVERSITY OF IL; TAIBL, J - UNIVERSITY OF IL; YANTIS, B - UNIVERSITY OF IL; KNOX, ROBERT - UNIVERSITY OF IL

Submitted to: National Hog Farmer
Publication Type: Trade Journal
Publication Acceptance Date: 12/15/2008
Publication Date: 12/29/2008
Citation: Spencer, K., Purdy, P.H., Blackburn, H.D., Spiller, S.F., Welsh, C.S., Stewart, T., Breen, S., Taibl, J., Yantis, B., Knox, R. 2008. Effect of number of motile sperm and number of inseminations using frozen boar semen on fertility in gilts. National Hog Farmer. http://nationalhogfarmer.com/genetics-reproduction/artificial-insemination/1215-boar-semen-use/.

Interpretive Summary: A study was conducted to determine the requirements for use and application of frozen boar semen in order to capture advantages for long term use, preservation, international distribution, disease protection, and access to limited genetic resources. A collaborative effort between the USDA, Purdue University, and the University of Illinois evaluated the fertility effects of 1, 2, or 4 billion frozen thawed motile sperm using single or double inseminations in gilts. Prepubertal gilts 180 days of age were treated to synchronize estrus. Multiple straws were thawed to create doses containing 1, 2, or 4 billion motile sperm per dose. Gilts were inseminated once at 32 hours or twice at 24 and 32 hours using conventional AI catheters. Estrus detection and real time ultrasound were each performed at 12 hour intervals to determine onset of heat and time of ovulation. There was no effect of either dose or number of inseminations on pregnancy rate, number of healthy fetuses, or on embryo survival. There was an effect of interval from insemination to ovulation on fetuses and embryo survival but not on pregnancy rate. Optimal insemination occurred within 8 hours before ovulation. Boar influenced number of fetuses, and embryo survival, but not pregnancy rate. Our results suggest that limited numbers of frozen thawed sperm can be used to establish acceptable pregnancy rates and litter sizes in gilts. There was little evidence for any advantage from using double insemination at 24 and 32 hours after onset of estrus, or for using higher numbers of sperm. This indicates that acceptable fertility can be achieved using single AI with 1-2 billion motile, frozen thawed sperm.

Technical Abstract: A study was conducted to determine the requirements for use and application of frozen boar semen in order to capture advantages for use long term preservation, international distribution, disease protection, and access to limited genetic resources. A collaborative effort between the USDA, Purdue University, and the University of Illinois evaluated the fertility effects of 1, 2, or 4 billion frozen thawed motile sperm using single or double inseminations in gilts. Semen was generously supplied courtesy of PIC from 6 selected sires with known fertility. Semen was collected and shipped to the USDA at Fort Collins for freezing in ½ cc straws. The semen was shipped in liquid nitrogen to the University of Illinois for use in the fertility trials at the University of Illinois swine research center. The experiment was conducted in 5 replicates using terminal line PIC gilts. Prepubertal gilts 180 days of age were treated with PG600 and then with MATRIX to synchronize estrus. All gilts that expressed estrus following Matrix withdrawal were assigned to treatment. Gilts were allotted to treatment with each boar represented across treatments. Multiple straws were thawed into Mini-tube thawing extender to create 80 cc AI doses containing 1, 2, or 4 billion motile sperm per dose. Semen was used within 1 hour of thawing. Gilts were inseminated once at 32 hours or twice at 24 and 32 hours using conventional AI catheters. Estrus detection and real time ultrasound were each performed at 12 hour intervals to determine onset of heat and to determine fertility and time of ovulation. Data were collected for interval from AI to ovulation, pregnancy and number of fetuses at day 24- 35. The data were analyzed using the mixed models procedures of SAS for the effect of dose, number of inseminations, replicate, boar, and interval from insemination of to ovulation where appropriate. There was no effect of either dose or number of inseminations on pregnancy rate, number of healthy fetuses, or on embryo survival (Table 1). There was an effect of interval from insemination to ovulation on fetuses and embryo survival (P<0.01) but not on pregnancy rate. Optimal insemination occurred within 8 hours before ovulation. Boar significantly influenced number of fetuses, and embryo survival, but not pregnancy rate. Our results suggest that limited numbers of frozen thawed sperm can be used to establish acceptable pregnancy rates and litter sizes in gilts. There was little evidence for any advantage from using double insemination at 24 and 32 hours after onset of estrus, or for using higher numbers of sperm. This indicates that acceptable fertility can be achieved using single AI with 1-2 billion motile, frozen thawed sperm. It was also evident, that boar did impact litter size and selection for fertility after freezing may be a necessary measure as well as motility. Lastly, the interval from AI to ovulation is an important limit to fertility, and methods which allow AI to occur within 8 hours of ovulation have the greatest potential for fertility.