title: B-mode ultrasonographic evaluation of paired testicular diameter of mature boars in relation to average total sperm numbers.
abstract: Crossbred, meat-type terminal sire boars (n = 215) were randomly assigned by age group (240-300, 301-360, 361-420, 421-480, 481-540, 541-600, and >721 days). Stud boars were on a once or twice weekly semen collection schedule. Testis diameters, in duplicate, were obtained using B-mode ultrasonography. Summation of average left and right testis diameter within boar gave the paired testicular diameter (PTD). Average ejaculate volume, sperm concentration (sperm/ml), and total sperm numbers for each boar were determined using composite data (average values) obtained from the last four semen collections. There was a <0.5cm difference between left and right testis diameters, with the left testis being the larger of the two testes (P = 0.03). There was no difference in PTD found between age groups in this study. Conversely, a dramatic increase in average total sperm numbers (ATSN) was observed between boars of 240-300 days (57.0+/-27.4 x 10(9) sperm) and up to 420 days (118.6+/-33.6 x 10(9) sperm) of age. The ATSN (127+/-32.5 x 10(9) sperm) remained constant for the 421-480 to >721-day age groups. The correlation between PTD and ATSN was low (r = 0.24) in this study. The results of this study demonstrate that normal boars should exhibit <0.5cm diameter difference between testes. As observed in other studies, the left testis was usually larger than the right testis. Correlation of total sperm numbers in a boar ejaculate using a composite ejaculate score (average values) and PTD measurements obtained using B-mode ultrasonography was poor when used in boars >8 months of age.
authors.affiliation: Department of Veterinary Clinical Medicine, University of Illinois, 1008 W. Hazelwood Dr., Urbana, IL 61802, USA. sclark@cvm.uiuc.edu
authors.forename: S G
authors.initials: SG
authors.lastname: Clark
authors.forename: D J
authors.initials: DJ
authors.lastname: Schaeffer
authors.forename: G C
authors.initials: GC
authors.lastname: Althouse
mesh_terms: D000375:Aging; D000818:Animals; D001947:Breeding; D008297:Male; D013076:Sperm Count; D013552:Swine / Q000033:anatomy & histology*; D013737:Testis / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D014463:Ultrasonography