Selection for Age at Puberty in Swine: Correlated Response in Sow Productivity

The objective was to examine correlated sow productivity characteristics from genetic lines (GL) divergently selected for age at puberty (AGEPUB). Selection on composite Landrace × Large White females resulted in two genetic selection lines, young AGEPUB (AP) and old AGEPUB (OLD). Data consisted of sows (n=332) from four generations (GEN) raised at the North Carolina Department of Agriculture Tidewater Research Station. Females were reared in a curtain-sided building with fully slatted floors and natural ventilation. Gilts were placed in pens of 15 (0.84 m² per pig). At 130 d of age, gilts were exposed to mature boars for 7 min/d for 90 d. Puberty was defined as first observed standing reflex in the presence of a boar. Traits included: total number born (TNB), litter birth weight (LBW), average piglet birth weight (BWT), BWT CV, litter weaning weight (LWW), average piglet weaning weight (WWT), WWT CV and litter size at weaning (LSW). Statistical analysis was performed in SAS using PROC GLM. Fixed effects included GL, GEN and GL × GEN. Covariates of TNB and LSW were included for BWT and BWT CV and WWT and WWT CV, respectively. In GEN 4, AP and OLD gilts obtained puberty at 162 and 177 d of age, respectively, and 85 and 50%, respectively, exhibited puberty. Total number born tended (P=0.07) to be greater for OLD when compared to AP (11.73 vs. 11.03) and LSW tended (P=0.06) to be greater for OLD when compared to AP (9.68 vs. 8.96). Both AP and OLD had similar (P>0.05) LBW (12.20 vs. 12.27 kg, respectively) and LWW (50.7 vs. 52.6 kg, respectively). Overall, AP had greater (P<0.05) BWT than OLD (1.12 vs. 1.07 kg). Yet in GEN 1, BWT did not differ (P>0.05) between AP and OLD (1.17 vs. 1.16 kg, respectively) but in GEN 4 AP had greater (P<0.01) BWT than OLD (1.09 vs. 1.00 kg). Similar to BWT, AP had greater (P<0.05) overall WWT than OLD (5.72 vs. 5.47 kg). Yet in GEN 1, WWT did not differ (P>0.05) between AP and OLD (5.75 vs. 5.66 kg, respectively) but in GEN 4 AP had greater (P<0.05) WWT than OLD (5.53 vs. 5.19 kg). Birth weight CV was greater (P<0.01) for AP when compared to OLD (17.7 vs. 15.8%) yet WWT CV was lower (P=0.05) for AP when compared to OLD (14.0 vs. 15.5%). Results suggest selection for AP may enhance piglet quality yet impair litter size.