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Testicular growth of 377 boars was compared by obtaining in situ measurements of testes width and length and excised tissue weights. Two experiments involved a line selected nine generations for ovulation rate (OR) and a control line (CL), and two experiments contained boars of the OR line and two other lines; WL, a Large White-Landrace cross, and a line founded by crossing lines OR and CL and selected six generations for increased average daily gain and decreased backfat (LG line). In situ testes measurements were similar for the OR and CL lines and were curvilinearly related to age. The LG line had smaller in situ measurements than the OR line (P less than .05) when both unadjusted means and means adjusted for body weight were compared. The OR line had 10.5% heavier testes than the CL line at 90.8 kg and a 9 to 15% advantage at 120, 141, 162 and 183 d of age. The OR line had more rapid testicular development from 120 to 183 d of age (P less than .05) than the CL line. The LG line had significantly lower excised testes weights (17 to 50% less), a lower percentage of tubules that showed active spermatogenesis and lower mean diameter of the seminiferous tubules (P less than .05) than the OR line. The relative differences between lines OR, CL and LG suggest that selection for lean growth rate has resulted in less rapid testicular development and increased age at puberty. The correlations of testes weights and in situ testes measurements taken at the time of castration were between .76 and .93. The correlations of testes width and testes length with epididymides weights were slightly lower, and correlations of body weight and testes weight ranged from .51 to .70. Mean diameter of the seminiferous tubules and percentage of tubules with active spermatogenesis were correlated with measurements of testes size (r = .50 to .61) and body weight at the time of castration (r = .29 to .36). Correlations of excised testes weights with number born in the boar's contemporary litter and ovulation rate of full sibs were uniformly positive. The correlations of measurements of testes size and backfat (r = -.09 to .20) suggest that the phenotypic relationship between testes growth and body composition is small. However, the response found in the LG line suggests a negative genetic relationship between lean growth rate and testicular growth rate.

The relationship of teat number to seven measures of female reproduction was evaluated in the University of Nebraska Gene Pool population. Teat number was recorded for 7,513 pigs, ovulation rate for 2,794 gilts and litter size and weight at birth and weaning (42 days) for 789 gilts. Paternal half-sib and full-sib analyses were used to estimate heritabilities for each trait and to estimate the genetic and phenotypic correlations of teat number with the measures of reproduction. The direct response to selection for ovulation rate and the correlated response in teat number were also evaluated from the regressions of line differences (Select-Control) on generation number (10 generations of selection) and cumulative selection differential for ovulation rate. The paternal half-sib heritabililty for teat number was .32, and the paternal half-sib heritabilities for ovulation rate and the litter traits were similar to previous estimates from this population. Most of the genetic and phenotypic correlations with teat number were negative and all were nonsignificant. The realized heritability for ovulation rate was .46 +/- .10. The regression of response in teat number on generation number number was .08 +/- .03 (P < .10). An estimate of .44 was obtained for the realized genetic correlation of teat number with ovulation rate.

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