REPRODUCTIVE AND TESTICULAR CHARACTERISTICS OF PUREBRED AND CROSSBRED BOARS

One-hundred-ninety-five Duroc (D), Hampshire (H), Duroc x Hampshire (D x H) and Hampshire x Duroc (H x D) boars were evaluated for reproductive performance. One-hundred- sixteen boars were castrated at approximately 225 days of age to evaluate testicular and epididymidal weights and sperm numbers. Testes from crossbred boars were 95.33 ± 22.81 g heavier (P\u3c.01) and contained 14.41 ± 3.92 billion more sperm (P\u3c.01) than those from purebred boars. Testes from Hampshire boars were 50.40 ± 31.75 g heavier with 6.27 ± 5.45 billion more sperm than those from Durocs. There were no significant differences between breeds for caput-corpus epididymidal measurements. Durocs had 24.55 ± 12.16 billion more sperm (P\u3c.05) in the cauda epididymis than Hampshire boars. Testes weight and testes sperm numbers were significantly correlated with caput-corpus epididymidal and cauda epididymidal sperm numbers. Correlations of testicular and epididymidal characteristics with growth rate and backfat to 100 kg were small and nonsignificant. Twenty 7.5-month to 9-month-old D1 D x H and H x D boars and 19 H boars were each mated to two Yorkshire gilts to evaluate reproductive efficiency. Conception rates were: D, 63.2%; D x H, 67.5%; H x D, 60.0%; and H, 48.6%. Number of embryos 30-days postbreeding was 10.66 ± .49 and 11.25 ± .43 (P\u3e.10) for gilts mated to purebred and crossbred sires, respectively. Twenty-eight of 36 crossbred boars mated each time they were exposed to an estrus gilt but only 11 of 36 of the purebred boars mated each time. None of the crossbred boars failed to mate more than once, while 15 of 36 purebred boars failed to mate two or more times. In general, differences among breed groups for time required to mount after exposure to estrus gilt and length of ejaculation time were small and nonsignificant