Effects of birth weight and standardized litter size on growth performance of boars and subsequent reproductive performance

The aim of this study was to investigate the effects of birth weight and rearing litter size on growth and reproductive performance of boars. One hundred and forty male piglets were allotted to two groups, based on litter size: a smaller litter (SL) (8 piglets/litter, 70 boars) and a larger litter (LL) (12 piglets/litter, 70 boars). The boars in these litters were separated into two birth weight subgroups: lower birth weight (LBW) (mean: 1.15 kg, 70 boars) and greater birth weight (GBW) (mean: 1.59 kg, 70 boars). Testes volume, sexual activity and semen quality of boars at 180 days old were evaluated. The males in the GBW group, when compared with the LBW group, had greater bodyweight at 21, 28, and 63 days old (P < 0.01) and 180 days old (P < 0.05), greater testes volume and semen volume (P < 0.05), greater sperm concentration and total number of sperm in the semen (P < 0.01) and a longer ejaculation time (P < 0.05). The boars in the SL group had greater (P < 0.01) bodyweight at 21 and 28 days old, greater (P < 0.05) sperm concentration and total number of sperm in the semen than boars in the LL group. These results indicate that birth weight is a good predictor of sperm production in adult boars and suggest the possibility of increasing sperm production in adult boars by reducing the litter size in which they are reared.