Relationships among scrotal and testicular characteristics, sperm production, and seminal quality in 129 beef bulls

Standard breeding soundness examinations plus measurement of scrotal surfac e temperature (SST), internal/scrotal testicular temperatures, testicular u ltrasonographic echotexture, daily sperm production, and epididymal sperm r eserves were conducted on 129, 16-month-old crossbred beef bulls. There wer e significant positive linear correlations between SST and internal scrotal /testicular temperatures, a positive linear regression (P < 0.06) of bottom SST with the incidence of secondary sperm defects, but a negative linear r egression (P < 0.01) with the incidence of primary sperm defects. Testicula r echotexture had a positive linear regression with daily sperm production (P < 0.002) and testicular tone had a negative linear regression (P < 0.008 ) with epididymal sperm reserves. Scrotal circumference had a positive line ar regression (P < 0.04) with the percentage of progressively motile sperm, a negative linear regression (P < 0.1) with the incidence of primary sperm defects, and a positive linear regression (P < 0.0001) with epididymal spe rm reserves. In addition to seminal quality and scrotal circumference, test icular ultrasonographic echotexture has considerable promise for augmenting breeding soundness examinations of bulls.