ARS | Publication request: Model for Evaluation of Testicular Development in Boars

Submitted to: Journal Of Animal Science Supplement
Publication Acceptance Date: November 20, 2003
Publication Date: August 1, 2004
Publisher's URL: www.asas.org
Citation: Ford, J.J., Lunstra, D.D., Wise, T.H., Rohrer, G.A. 2004. Model For Evaluation Of Testicular Development In Boars [abstract]. Journal Of Animal Science 82 (Supplement 2):89.

Technical Abstract: Sperm production of boars is positively associated with testicular wt. A QTL for testis size on chromosome X was identified in a line of one-half Meishan crossbred pigs. This line was mated to Landrace x Yorkshire crossbreds followed by three generations of inter se mating. Sixteen gilts, heterozygous for the testis-size QTL, were selected from the third generation and mated to produce littermate boars to investigate testis size. Boars from one-half of these litters were unilaterally castrated at 25 d of age, and the remaining litters were unilaterally castrated at 56 d to relate early Sertoli cell development to subsequent testicular size. At 10 mo of age the remaining testis was removed and weighed; boars within litters were classified as having the smallest (SM, n=13), largest (LR, n=13) or intermediate testis wt (IN, n=22) yielding mean testis wt of 312, 419 and 579 g for SM, IN and LR boars, respectively. Birth wt was less for SM than LR boars (P<0.01, 1.14 vs 1.34 kg). Body wt at 10 mo remained different for these two groups (P<0.01; 136 vs 149 kg) with IN boars being intermediate. Plasma FSH at 4 and 10 mo and TSH at 4 mo were negatively correlated with testis wt at 10 mo (P<0.05); IN boars were intermediate for both plasma FSH and TSH. Seminiferous tubule diameter of boars unilaterally castrated at 25 d was similar for SM, IN, and LR boars but was greater (P<0.01) at 56 d in SM than in LR boars. Color of testis at 10 mo was darker in SM than in LR boars with IN boars being intermediate. The QTL for small testes was in 9/13 SM, 11/22 IN, and 2/13 LR boars indicating that this X-chromosome QTL influences testis size, but factors other than genes associated with this QTL also impact testicular development. Gilts that were heterogeneous for the testis-size QTL produced littermate boars that varied significantly in testis wt. Boars that ultimately developed small testes had greater FSH secretion and earlier pubertal development than boars that developed large testes. This model will be useful to investigate factors that regulate testis development.