Growth response of low and average birthweight pigs to sow lactation feed intake

Application Growth performance of low birthweight (BW) pigs increased significantly (12.4%) in response to a 24% increase in sow lactation feed intake. This work demonstrates that compromised piglets have the potential to achieve an acceptable wean weight if effective intervention strategies are employed. Introduction Increased litter sizes currently present in modern commercial sow herds have resulted in elevated numbers of low BW pigs with higher pre-weaning mortality, lower weaning weights and reduced lifetime performance (Fix et al, 2010). Furthermore, differences in weaning weight often increase further throughout the growing and finishing periods (Williams, 2003). Therefore development of intervention strategies which maximise weaning weight and lifetime performance of compromised pigs are important to enhance overall herd performance and profitability. This work aimed to assess the growth response of low and average birth weight piglets to different levels of lactation sow feed intake. Material and methods A two (birth weight) x two (lactation feed allowance) factorial design study employing 32 litters (448 pigs) across 8 replicates was undertaken at AFBI Hillsborough. In each replicate four sows, balanced for parity and body condition, acted as foster mothers. Within 24 hours of farrowing, two litters of 14 low BW pigs (<1kg) and two litters of 14 average BW pigs (1.25kg-1.75kg) were randomly assigned to the foster mothers. Lactation feed allowance was offered at either a high (HFA) or a low (LFA), albeit commercially standard, level. The low level allowance (LFA) offered 3kg at farrowing with increments of 0.3kg/day and was capped at 7.5kg/day whereas the high allowance (HFA) offered 3kg on the day of farrowing, increasing by 0.5kg/day up to maximum of 11kg/day. Weaning was undertaken at 28 days. At farrowing and weaning, sow back fat depth at the P2 position was quantified using an ultrasound scanner. Piglets had individual health, vitality and liveweight recorded throughout lactation. Suckling behaviour was also monitored over a 24 hr period at day 7. Relative growth was calculated by dividing weight gain to weaning by birth weight. Results There were no significant interactions between treatments on any of the health or performance parameters recorded for sows or piglets (Table 1). Average feed intake of sows offered the HFA was 217kg whilst sows offered the LFA consumed an average of 174kg representing a difference of 24.7%. As expected, at weaning average BW pigs were heavier than low BW piglets but they had a lower relative growth rate (Table 1). Litters of low BW piglets had a higher mortality rate and were fewer in number at weaning as a result compared with litters of average birth weight piglets. Sows rearing litters of average BW lost more back fat. A HFA increased piglet wean weight and litter gain as well as relative growth rate but had no effect on litter mortality or back fat loss during lactation (Table 1). Analysis comparing the individual treatments found that there was no significant difference in weaning weight or litter gain between low BW litters offered a HFA and average BW litters offered a LFA. Pre-wean mortality was significantly higher for low BW litters offered a LFA compared to all other treatment groups (P=0.012). The back fat loss of sows rearing average BW litters and offered a LFA was significantly higher than that for all other treatments (P= 0.02). Conclusion The performance of sows and piglets on the low allowance feeding regimen was reflective of commercial practice. However, this work demonstrated that sows were capable of enhanced intakes when offered a higher lactation feed allowance. This allowed compromised piglets to express a weaning weight matching that of average BW pigs reared under commercial like conditions and record a significantly reduced pre-wean mortality. Overall it is concluded that low BW piglets have a higher potential to grow, relative to their birth weight and can respond positively when provided with an increased milk allowance from the sow.