Effect of season on scrotal circumference, semen characteristics and testosterone serumconcentration in Mexican Corriente and other beef breed bulls

ABSTRACT

To evaluate the effects of season on semen,scrotal circumference and testosterone concentration inCorriente and European-breed bulls, 758 samples wereanalyzed in four years. Comparisons were madebetween bulls of the same breed in different seasons andbetween bulls of different breeds in the same season.Scrotal circumference of both breeds was higher in thesummer and autumn (P < 0.01). Sperm concentration,individual motility and live cells were lower in summerand autumn in European-breed bulls (P < 0.01). Allpercentages of sperm defects were higher, andtestosterone was lower in European-breed bulls duringsummer and autumn (P < 0.01). Gross motility tended tobe lower (P = 0.09) in European-based bulls duringwinter. Scrotal circumference was higher in Europeanbreedbulls than Corriente bulls in all seasons (P < 0.01).Ejaculate volume and sperm concentration were similarin Corriente and European-breed bulls in all seasons(P > 0.1). Individual motility was lower in Europeanbreedthan in Corriente bulls in summer and autumn(P < 0.01 and <0.01). Live cells count was lower inEuropean-breed than in Corriente bulls during thesummer and autumn (P < 0.01 and <0.01). Major spermdefects were higher for Corriente than European-breedbulls during winter (P < 0.01). Minor cell defects werehigher in summer and autumn (P < 0.01) in Europeanbreedthan in Corriente bulls. Total defects were lowerin Corriente than in European-breed bulls duringsummer and autumn (P < 0.01), and higher duringwinter (P < 0.01). Testosterone was higher in Corrientebulls during summer (P < 0.01) and autumn (P < 0.01)than in European-breed bulls. Gross motility was lower(P < 0.05) in European-breed than in Corriente bulls inwinter. Season had no effect on most semencharacteristics in Corriente bulls, while European-breedbulls had lower semen quality during the hotter seasons.(AU)