Low birth weight affects lifetime productive performance and longevity of female swine

It is commonly known that large litter size leads to lower average birth weights, with more piglets born weighing <1 kg, resulting in a negative impact on piglet growth performance. Conversely, there are few studies showing the long-term impact of low birth weight on productive performance of female piglets selected for the breeding herd. The aim of this study was to evaluate the effects of birth weight on reproductive performance and longevity up to the third farrowing of Landrace x Large White crossbred gilts. For most variables, 835 gilts selected for breeding were included in the analyses. When the analysis concerned the number of days in the herd from birth onwards, data from 1495 females were analyzed. Gilts were retrospectively classified into eight classes of birth weight (BiW), with approximately 12.5% of gilts in each group. Overall, gilts were 196.8±0.6 days old at first estrus manifestation, which occurred in 23.8%, 44.4% and 64.6% of gilts within 10, 20 and 30 days of boar exposure, respectively, with no difference (P>0.05) among BiW classes. Age at puberty was similar among BiW classes in gilts that showed estrus within 30 d of boar exposure (P≥0.428), but PG600-gilts weighing 410–1160 g reached the puberty later than those weighing >1400 g (P<0.05). Removal due to anestrous was higher (P≤0.093) in female piglets of 410–990 g (22.9%) compared with the other BiW classes (overall 9.6%). There were no differences among BiW classes in the first (P=0.480) and second (P=0.400) farrowing rate but piglets of 1000–1160 g and 1510–1610 g had lower third farrowing rate (P=0.041) than piglets weighing >1620 g. The total number of piglets born (P=0.08) and piglets born alive (P=0.028) were lower for the lightest BiW class in the first farrowing but they were similar among BiW classes in the second and third farrowing. The percentage of first-mated gilts that reached the third farrowing (68.7%) was not affected by BiW (P>0.05). The third farrowing was reached at 627.4±1.17 days of age on average, with no significant difference among BiW classes (P=0.806). Females born weighing less than 1 kg produced about 4.5 fewer piglets along three parities than the other BiW classes (P≤0.05). Female piglets weighing between 1.0 and 1.28 kg at birth were also negatively affected in terms of lifetime herd days, although to a less extent than those weighing less than 1 kg, in comparison with piglets weighing >1.28 kg. However, the number of herd days, from selection for entry into the breeding herd to the third farrowing or removal, was not different (P=0.257) among BiW classes. The results of this study show that low BiW (<1 kg) negatively influences the production of piglets and longevity of female swine.