In vitro maturation and fertilization techniques for assessment of semen quality and boar fertility

The reliability of using different in vitro-derived measures of sperm quali ty to predict boar fertility was examined. On three occasions during a 20-w k period of breeding, special collections of the first sperm-rich fraction of the ejaculate from six boars were carried out. After in vitro capacitati on procedures, three dilutions (5 x 10(5), 1.25 x 10(5), and 3.125 x 10(4) sperm/mL) of these semen samples were used in a standardized in vitro ferti lization (IVF) test with oocytes recovered from prepubertal slaughterhouse ovaries and matured in vitro. Routine assessments of sperm motility, concen tration, and morphology were also carried out for all collections used for Al during the 20-wk period. Semen from the same ejaculate, processed accord ing to normal commercial practice using the AndroHEP extender, was used to inseminate equal numbers of recently weaned sows with either 3 x 10(9) or 2 x 10(9) total sperm, three times during the estrous period. Data from a to tal of 444 sows were used to determine boar fertility; between 12 and 54 so ws were bred with each semen dose across the six boars. All measures of spe rm fertilizing ability in vitro were different among boars (all P < .05) an d use of different semen dilutions for IVF allowed further discrimination o f apparent sperm quality among boars. The laboratory evaluation of semen co llected during the period of breeding indicated effects of boar on ejaculat e volume, total number of sperm per ejaculate, motility, and the percentage of sperm with normal morphology (all P < .01). Sperm dose used in Al had n o effect on farrowing rate (80.7 vs 81.5%), but the lower Al dose resulted in a reduction (P < .05) in total numbers born (10.8 vs 10.0). For all thre e semen dilutions, estimated potential embryo production rate accounted for up to 70% of the variation in litter size obtained with 3 x 10(9) sperm pe r Al dose, and the number of sperm attached per oocyte was a major factor a ccounting for variation in litter size obtained with 2 x 10(9) sperm per Al dose. These IVF variables may, therefore, be effective indicators of boar sperm quality for use in Al. With 2 x 10(9) sperm per Al dose, the percenta ge of sperm with normal morphology also explained a large part of the varia nce in litter size born (R-2 = .59), indicating that morphological characte ristics are a useful measure of semen quality.