Reproductive performance of rams that failed breeding soundness evaluation: The need to reconsider the evaluation

Abstract

Breeding soundness evaluations for sires closely followed the introduction of electro-ejaculation as a tool for the measurement of bull fertility in 1950. Quickly following the establishment of bull breeding soundness evaluations, similar criteria were established for rams. It is intuitive that structural soundness, body condition, testes size and palpable consistency, as well as semen parameters are important for fertility. The value of a breeding soundness evaluation as evidenced by ram fertility is lacking. Rams (n = 55) were subjected to an industry standard breeding soundness evaluation (BSE). Regardless of the BSE outcome rams were placed in a competitive breeding environment (approximately 1:30 ram:ewe). Genomic DNA was extracted from rams and approximately one-third of the lambs (n = 468) and their dams (n = 379). Microsatellite markers were used to determine parentage. Rams that passed the BSE (n = 37) did not (P = 0.86) sire more lambs (8.7 ± 1.7) than rams that failed BSE (n = 18; 8.2 ± 2.3). Both rams that passed or failed the BSE had zero identified offspring (32.4% of rams with passed; 22.2% of rams with failed) and did not differ (P = 0.54) by BSE status. Notably, the ram with the greatest number of identified offspring had a failed BSE siring more than three times the 99% confidence interval for expected number of lambs. While this small study does not warrant wholesale dismissal of BSE, it does give pause to the ram BSE and perhaps what constitutes a satisfactory breeder should be reconsidered.