EVALUATION OF DIETARY PHYTOESTROGEN EXPOSURE ON GROWTH, SEMEN PARAMETERS, AND REPRODUCTIVE ANATOMY DEVELOPMENT OF GROWING ANGUS BULLS

This study evaluated effects of phytoestrogen on scrotal growth and semen quality in bulls. Spring-born, Angus bulls were used in consecutive years (n = 39, year 1; n = 24, year 2) and stratified by weaning weight, age of dam (AOD), and sire. Dietary treatments included soybean meal (SBM) or cottonseed meal as protein source (CSM). At weaning, bulls were randomly assigned to treatment. Scrotal circumference was measured on d 0, 21, 54, and 86 and semen quality assessed on d 86. A treatment × year interaction was detected for circumference (P ≤ 0.05). Scrotal growth d 0 to 21, 54 to 86, and 0 to 86 was greater for SBM both years (P ≤ 0.05). Semen concentration from younger cows was higher (P ≤ 0.03) with SBM both years whereas CSM in 5+ older dam concentration was greater in year 2 (P < 0.0001). A diet × AOD (year) interaction influenced motility (P < .0001). Phytoestrogens from soybean meal improved scrotal growth and semen quality particularly with younger dams.