Breeding soundness examination of North American bison bulls.
OBJECTIVE
To evaluate the breeding soundness examination procedure in plains bison bulls.


METHODS
Multiyear (1993 through 1997) cross-sectional clinical procedure evaluation.


METHODS
Two hundred thirty-four 28- to 30-month-old bison bulls at Custer State Park.


METHODS
Breeding soundness examinations were performed on all bison bulls using 1992 Society for Theriogenology guidelines for beef cattle semen evaluation and reproductive tract examination. Linear and logistic regression analyses were used to detect correlations and associations among breeding soundness examination variables.


RESULTS
Scrotal circumference (SC) was significantly correlated with body weight, percentage of normal spermatozoa, percentage of primary spermatozoal defects, and percentage of motile spermatozoa. Scrotal circumference was positively associated with increased odds of semen collection, satisfactory motility (> or = 30% motility), satisfactory morphology (> or = 70% normal spermatozoa), and simultaneous satisfactory motility and morphology. Receiver-operator characteristic curve analysis selected 29 cm as the optimal SC cutoff most predictive of simultaneous satisfactory spermatozoal motility and morphology. Only 36.2% (83/229) of the bison bulls had a SC of 29 cm or greater and satisfactory spermatozoal motility and morphology.


CONCLUSIONS
SC is a good indicator of adequate spermatozoal motility and structure in bison. We recommend use of 30% spermatozoal motility, 70% normal spermatozoal morphology, and 29-cm SC as minimal satisfactory measurements for breeding soundness examinations of 28- to 30-month-old bison bulls that have been raised on forage-based nutrition.
Keen
J E
JE
USDA, Agricultural Research Service, US Meat Animal Research Center, Clay Center, NE, USA.
Rupp
G P
GP
Wittenberg
P A
PA
Walker
R E
RE
D000818:Animals; D016164:Bison / Q000033:anatomy & histology* / Q000502:physiology*; D001835:Body Weight; D001947:Breeding; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005837:Genitalia, Male / Q000033:anatomy & histology; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D010808:Physical Examination / Q000662:veterinary; D012372:ROC Curve; D012611:Scrotum / Q000033:anatomy & histology; D012661:Semen / Q000166:cytology / Q000502:physiology; D013081:Sperm Motility; D013094:Spermatozoa / Q000648:ultrastructure