Impact of sow lactation feed intake on the growth and suckling behaviour of low and average birthweight pigs to ten weeks of age

Improved genetics in commercial pig production have resulted in larger litter sizes. However this has increased the prevalence of compromised pigs exhibiting inferior birthweights, weaning weights and lifetime performance. This study aimed to determine the effects of increased sow lactation feed intake on growth of low and average birthweight piglets until 10 weeks of age. Low (LOW BW;<1kg) and average (AV BW;1.3-1.7kg) birthweight animals were reared in uniformly weighted litters comprising 14 piglets on a foster mother offered either a low (LOW FA; max 7.5kg/day) or high (HIGH FA; max 11kg/day) feed allowance over a 28 ± 1 day lactation. Piglet performance was monitored from birth until ten weeks of age. Sows offered a High FA consumed 42.5kg more feed on average than those offered Low FA, resulting in a greater derived milk yield (P<0.05). Animals of Av BW remained heavier than Low BW pigs throughout the trial (P<0.05). Piglets reared by High FA sows were heavier at week 3, 4, 5 and 7 (P<0.05) but not week 10 (P>0.05). Growth rate of piglets relative to their birthweight was significantly greater for Low BW piglets than those of Av BW during lactation (P<0.001). Piglets reared by sows offered a High FA expressed greater relative growth pre-weaning (P<0.05), however post-weaning relative growth for piglets reared on sows offered a Low FA was greater (P<0.05) suggesting compensatory growth. Neither birthweight nor sow feed allowance significantly affected pre-weaning mortality (P>0.05). However Low BW animals on sows with a High FA recorded half the pre-weaning mortality of Low BW pigs on sows with a Low FA. During week 1 of lactation, Av BW litters recorded a greater total suckling duration compared to Low BW litters (P<0.05) but there was no difference in suckling frequency (P>0.05). During week 3 of lactation High FA litters displayed a significantly lower suckling frequency (P<0.05) yet a greater total suckling duration (P<0.001). Average daily gain was greater for Av BW pigs during weeks 4 to 7 (P<0.001) but no difference was recorded between week 7 and 10 (P>0.05). Average daily feed intake was greater for Av BW pigs throughout the nursery period (P<0.05) but feed-conversion ratio did not differ compared to Low BW pens (P>0.05). In conclusion offering sows a High FA increased weaning weight of all animals, however birthweight was the major determinant of post-weaning performance.