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ARS Home » Research » Publications at this Location » Publication #93505
Title: BREEDING SOUNDNESS EXAMINATION OF NORTH AMERICAN BISON BULLS

Author
item Keen, James
item RUPP, GARY - UNIVERSITY OF NEBRASKA
item WITTENBERG, PAUL - FALL RIVER VET CLINIC, SD
item WALKER, RONALD - CUSTER STATE PARK, SD

Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Bison ranching is a rapidly growing alternative agriculture industry in the U.S. Breeding soundness examination (BSE), which consists of a general physical examination, careful male reproductive system evaluation, & semen collection & analysis, has been utilized by veterinarians for 40 yrs to identify bulls with a high likelihood of success as a sire. However, BSE of bison has not been previously described. In this report, 234 bison bulls from 1993-97 were evaluated for reproductive soundness at 28-30 mo of age using Soc. for Theriogenol. beef bull guidelines to define minimal satisfactory semen motility (>-30% motility) & semen morphology (i.e. >=70% normal sperm). Scrotal circumference (SC, a measure of a bull's capacity to produce sperm) was significantly correlated with body weight, % normal sperm, % primary sperm defects & % sperm motility. SC was also positively associated with satisfactory sperm motility (viability) & sperm morphology. Percent motility was correlated with % normal sperm, % primary sperm defects, & % secondary sperm defects. Receiver-operator characteristic curve analysis selected 29 cm as the optimal SC cutoff most predictive of simultaneous satisfactory motility & morphology. Only 36% of bison bulls had satisfactory motility, morphology, & a SC of 29 cm or greater. These BSE findings in bison bulls are quantitatively & qualitatively similar to those in beef cattle, and suggest that BSE in bison bulls may be a valuable management tool.

Technical Abstract: Objective: Describe & evaluate breeding soundness examination (BSE) procedure in bison bulls. Design: Multi-year cross-sectional clinical procedure evaluation. Sample Population: 234 28- to 30-mo-old bison bull candidates for herd replacement or public sale at Custer State Park, Custer, SD, from 1993-1997. Procedure: BSEs were performed on all bison bulls using 1992 Soc. for Theriogenol. guidelines for beef cattle for semen evaluation & reproductive tract examination. Linear & logistic regression were used to detect correlations & associations among BSE variables. Results: Scrotal circumference (SC) was significantly correlated with body weight, % normal sperm, % primary sperm defects, & % sperm motility. Increasing SC was positively associated with increased odds of semen collection, satisfactory motility (>=30% motility), satisfactory morphology (>=70% normal sperm), & simultaneous satisfactory motility & morphology. Sperm morphology (esp. mid-piece, tail, & separated head sperm defects) was associated with motility. Receiver-operator characteristic curve analysis selected 29 cm as the optimal SC cutoff most predictive of simultaneous satisfactory sperm motility & semen morphology. Only 36.2% of the bison bulls had satisfactory motility, morphology, & a SC of 29 cm or greater. Implications: SC is a good marker of male reproductive soundness in bison. We recommend use of 30% sperm motility, 70% normal sperm morphology, & 29 cm SC as minimal satisfactory measurements for BSEs on bison bulls 28-30 mo of age developed on forage-based nutrition.