Piglet birth weight and litter uniformity were studied by first-named author, J.G.M. Wientjes of Wageningen University in the Netherlands and co-authors there and at the Institute for Pig Genetics (IPG).

In a paper published in Journal of Animal Science, they explain that they examined sows of different parities and crossbred lines in relation to: 1) weaning-to-pregnancy interval (WPI) and 2) sow body condition changes (in bodyweight and backfat thickness) during lactation and gestation in sows with a short WPI (seven days or less).

At the IPG research farm, individual piglet birth weights and sow body condition (bodyweight and backfat thickness at farrowing and weaning) were measured for 949 Topigs20 and 889 Topigs40 sows with more than four piglets born, inseminated between 2003 and 2011.

In all analyses, mean piglet birth weight and birth weight standard deviation (SD) and co-efficient of variation (CV) were corrected for total number born.

Total number born was greater in sows with a WPI of between eight and 21 days (+1.2 piglets; n=72) and more than 21 days (+0.7 piglets; n=182) than in sows with a WPI of seven days or less (P<0.01; n=1,584).

Mean piglet birth weight was not affected by WPI. Birth weight SD (–23 g) and CV (–1.7 per cent) were lower in sows with a WPI over 21 days than those with a WPI of seven days or less (P<0.01).

Effects of WPI were independent of sow parity.

Effects of body condition changes in sows with a WPI of seven days or less were studied separately in Topigs20 sows inseminated between 2006 and 2011 (n=808) and in Topigs40 sows inseminated between 2003 and 2008 (n=747).

Sow body condition loss during lactation was not related with subsequent total number born or mean piglet birth weight. Only in Topigs20 sows, more bodyweight loss during lactation was related with greater subsequent birth weight SD (β=0.83g/kg, P<0.01; β=1.62g/per cent; P<0.01). Additionally, more backfat loss during lactation was related with greater subsequent birth weight SD (β=5.11g per mm, P<0.01) and CV (β=0.36 per cent/mm, P<0.01), independent of sow parity.

Sow bodyweight increase during gestation was negatively related with total number born: Topigs20: β=-0.06 and –0.05 piglet per kg bodyweight increase for parity 2 (P<0.01), and 3 and 4 (P<0.01), respectively; Topigs40: β=–0.04 piglet per kg bodyweight increase (P<0.01), independent of sow parity.

Sow bodyweight increase during gestation was positively related with birth weight SD: Topigs20: β=0.63g per kg bodyweight increase (P=0.01), independent of sow parity.

Sow body condition increase during gestation was not related with mean piglet birth weight.

The researchers concluded that litter uniformity is compromised by severe sow body condition loss during lactation and improved in sows with a prolonged WPI. They suggest that these effects are likely related with insufficient restoration of follicle development.

Reference

^{Wientjes J.G.M., N.M. Soede, E.F. Knol, H. van den Brand and B. Kemp. 2013. Piglet birth weight and litter uniformity: Effects of weaning-to-pregnancy interval and body condition changes in sows of different parities and crossbred lines. J. Anim. Sci. 91(5):2099-2107. doi: 10.2527/jas.2012-5659}

August 2013