Enhanced fertility prediction of cryopreserved boar spermatozoa using novel sperm function assessment

Authors: DAIGNEAULT, BRADFORD - University Of Illinois; MCNAMARA, KELLI - University Of Illinois; Purdy, Phil; KRISHER, REBECCA - University Of Illinois; KNOX, ROBERT - University Of Illinois; RODRIGUEZ-ZAS, SANDRA - University Of Illinois; MILLER, DAVID - University Of Illinois

Submitted to: Journal of Andrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2015
Publication Date: 5/1/2015
Citation: Daigneault, B.W., Mcnamara, K.A., Purdy, P.H., Krisher, R.L., Knox, R.V., Rodriguez-Zas, S.L., Miller, D.J. 2015. Enhanced fertility prediction of cryopreserved boar spermatozoa using novel sperm function assessment. Journal of Andrology. 3:558-568.

Interpretive Summary: Cryopreserved semen is seldom used for commercial porcine artificial insemination despite many advantages that cryopreservation provides. Compared to fresh semen, the fertility of frozen-thawed boar sperm is more variable but usually less. Predicting the fertility of individual ejaculates for selection of higher quality semen prior to artificial insemination would increase overall success. Our objective was to test novel (oviduct and zona binding assays) and traditional (sperm motility, membrane integrity and IVF) laboratory analyses to identify characteristics of cryopreserved sperm that are related to boar fertility. Traditional post-thaw analyses of sperm motility and membrane integrity, in vitro fertility characteristics and novel sperm-oviduct binding tests were used to evaluate the fertilizing potential of each boar. The results indicated that the fertility of cryopreserved boar sperm may be predicted by utilizing traditional and novel laboratory tests that consider multiple functions of sperm.

Technical Abstract: Cryopreserved semen is seldom used for commercial porcine artificial insemination (AI) despite many advantages that cryopreservation provides. Compared to fresh semen, the fertility of frozen-thawed boar sperm is more variable but usually less. Predicting the fertility of individual ejaculates for selection of higher quality semen prior to AI would increase overall success. Our objective was to test novel and traditional laboratory analyses to identify characteristics of cryopreserved sperm that are related to boar fertility. Traditional post-thaw analyses of motility, viability and acrosome integrity were evaluated. IVF, cleavage and blastocyst development were also determined. Finally, a sperm-oviduct binding assay and a competitive zona binding assay were applied to calculate sperm adhesion to these two matrices. Fertility of the same ejaculates subjected to lab assays was determined for each boar by AI and defined as (1) the mean percentage of the litter sired and (2) the mean number of piglets sired in each litter. Means of each lab evaluation were individually modeled by boar and those values were applied to multiple linear regression analyses to determine which sperm traits could collectively estimate fertility in the simplest model. The regression model to predict the percent of litter sired by boar was effective (p < 0.001, R2 = 0.87) and included 5 traits; acrosome compromised sperm, percent live sperm (0 and 60 min post-thaw), proportion of motile sperm and the number of zona-bound sperm. The same model also predicted the number of piglets sired by boar (p < 0.05, R2 = 0.57). These models indicate that the fertility of cryopreserved boar sperm can be predicted effectively by including traditional and novel laboratory assays that consider multiple functions of sperm. Inclusion of novel sperm functional traits with traditional traits provided highly accurate fertility prediction.