Genetic parameters for testes traits in swine.

Data were collected from 1,245 Duroc boars and 527 Yorkshire boars. This represents 128 Duroc and 57 Yorkshire sires. Body weights, testis length and combined testes width at 140 and 168 d were obtained. Of these boars, 432 were castrated at a later age to evaluate relationships between in situ measures and excised testis traits. Heritabilities for testis length, width and volume at 140 d ranged from .16 to .25 in both Duroc and Yorkshire data. Heritabilities for testis measurements at 168 d ranged from .16 to .36 in both data sets. Favorable negative genetic relationships were found between in situ testis measures and age to 104 kg and backfat adjusted to 104 kg. Correlations among in situ measurements were high and positive. All excised testicular traits were highly heritable except for right epididymis weight and excised testis width. Correlation estimates among excised testis traits were generally positive. Phenotypic and genetic correlation estimates between live (in situ testis and growth performance traits) measurements and excised testis traits were generally favorable. This study suggests that in situ testis measurements should be good predictors of sperm production. It also suggests that selection for testis size should not be antagonistic to selection for growth performance traits.