Small piglet management

Piglets that are much smaller than their litter mates can take longer to grow and may need extra care. Use this guidance to reduce the difference in weight between light pigs and their heavier littermates.
Back to: Weaning and small pig management

Light pig syndrome

Defined as having a body weight (BW) at a certain age which is significantly below the average of the group and which grows markedly slower than their counterparts.

Associated problems

  • Increased weight and size variation within groups (in any stage of production)
  • Inefficient pen utilisation
  • Financial penalties at the abattoir for poor grading specification
  • Management difficulties and system inefficiencies
  • Increased labour and/or sorting equipment

Management of low birth weight pigs on farm

Many units have litters consisting of varying birth weights. These can become more varied, and, on average smaller, the higher the number born alive.

Whole litters consisting solely of small piglets are not necessarily a problem, as the piglets may still be viable. Low birth weight pigs have the capacity to grow at the same rate as normal birth weight pigs under the correct conditions, however, early intervention is critical.

If piglets weigh less than 1 kg, their chances of survival are poor. Regularly weigh litters and record averages over the year. When averages start to drop, review the system with your vet. Weigh small pigs so you can quantify how many are below 1 kg.

Currently, the industry attempts to deal with this problem by remixing pigs based on liveweight or removing them from the system, as there have been no clear recommendations for treatment. Research into how birth weight is influenced to improve the postnatal performance of lightweight pigs has resulted in the following guidance.

Foetal environment

  • Poor foetuses and the reduced growth of runt piglets can be identified as early as day 30 of gestation
  • Low birth weight can be a result of an inefficiency of the placenta to transfer nutrients to the foetuses rather than uterine capacity
  • Oxygen deprivation is the ultimate constraint on foetal growth and development. It influences piglet weight and the central nervous system and, ultimately, survival
  • You can get small but ‘perfectly formed’ piglets that show good vigour and good postnatal behaviours (e.g. suckling quickly), which aid their survival
  • Small and non-vigorous (probably oxygen deprived) piglets are at a great disadvantage
  • Maternal genotype influences the placental efficiency and, therefore, foetal weight even though the potential for growth and size is influenced by the sire line

Breeding herd nutrition

Focus on more than the last third of gestation (the time when foetuses have a growth spurt and birth weight can still be influenced). Increase nutrient intake by sows from day 80 of gestation to positively affect birth weight (from day 90–115 piglet growth rate increases substantially).

Review your young breeding gilts’ feeding regime. There can be short- and long-term effects on young gilts if you overfeed them during the early stages of gestation. Young gilts may partition the extra feed towards their own reserves rather than the growing foetuses. This can result in small piglets and fat gilts. Once a gilt is fat, she may continue to be non-productive.

Discuss late stage gestation nutrition with your feed provider if you feel improvements can be made.


If you have a closed herd, select breeding stock from sows and gilts that have produced good viable litters. This indicates that their placental efficiency is good and providing ample oxygen and nutrition exchange

Newborn management

Being present at farrowing is a critical part of good farrowing house management and means you can maximise colostrum intake in the first six hours after birth (achieving at least 100 ml intake by 16 hours post-farrowing).

It also enables you to help vulnerable piglets gain access to teats and suckle. Ensure they can suckle unhindered and then mark each piglet once you have seen them suckle.

Monitoring farrowing means you can also check for signs of ill health and treat according to your veterinary protocol. Ensure piglets are lying either on or under the heat source and not piling together, which would suggest they are cold.


Observe piglet behaviour and look out for fading piglets, take remedial action by fostering and providing electrolytes or additional milk.

Selective cross-fostering of low birth weight pigs with similar weight littermates can improve birth-to-weaning average daily gain (ADG) and pre-weaning performance.

It is a disadvantage for small piglets to have to compete with larger littermates and litters of small piglets should be created from all the ‘smalls’ born in a given farrowing day. Foster-litters of small piglets should be put with low-parity sows – the teat size of a low-parity sow will match the small mouths of the piglets.

Pre-weaning management

A non-competitive environment is important for low birth weight pigs in early life; this can be achieved, for example, by cross-fostering.

Provision of supplementary milk can reduce birth weight variation to slaughter weight, although does not always benefit overall performance.

The combination of these two management techniques will ensure costs are kept low, rather than providing supplementary milk to an unnecessary large number of litters.

Post-weaning nutrition

Improving nutrition, rather than upping the levels of feed, may be something to consider. The correct choice of starter feed regime is critical to minimise the post-weaning growth check as piglets transition from liquid to solid feed.

Feeding a high specification starter diet, with extra feed (corresponding to the last diet of the starter regime), could improve low birth weight pig performance to 10 weeks of age, and result in a similar nursery exit weight of low birth weight and normal birth weight pigs.

Feeding a high specification diet was not effective when offered from nine weeks of age, suggesting a critical window for intervention.

Research suggests that not only can low birth weight pigs benefit from an improved dietary regime, but that it is cost-effective for producers with an increased return per pig, and should be preferred to a standard commercial regime, which has a poorer margin over feed cost. For normal birth weight pigs, the standard commercial regime was the least expensive and had the greatest margin over feed cost.

Separation of pigs with low birth weight at weaning will allow selective feeding of an improved regime, as heavier pigs are best suited to a standard commercial diet.

Additional research has shown that nutritional treatments at different stages can affect the outcome:

  • Specialised diets fed at weaning can improve performance to the end of the nursery phase and are more cost-effective than feeding a standard commercial regime
  • Provision of supplementary milk does not benefit low birth weight piglet performance, but it does reduce the BW variation in mixed litters
  • Low birth weight pigs may not benefit from a diet higher in amino acids: energy fed at nine weeks of age (growers)

Economic implications of low birth weight pigs

Contrary to current assumptions, low birth weight pigs can perform very well if managed and fed appropriately. Improved growth rates and low pre-weaning mortality rates can be achieved with extra care of low birth weight pigs.

The economic impact of rearing low birth weight pigs will depend on:

  • Their ability to convert feed efficiently
  • Financial penalties at the abattoir
  • Costs associated with managing variation during production
  • Current pig and feed prices


  • Birth weight can have a significant effect on future growth, with initial differences in body weight continuing with age
  • Weaning weight also plays a critical role. Any additional weight that is gained as a result of treatment is likely to be retained at slaughter
  • Environmental factors at different stages of production may limit the growth of low birth weight pigs
  • Nutritional treatments at different stages of production (lactation, weaner, grower) can affect the outcomes
  • If provided with optimal dietary regime, this can be exploited to reduce the difference in weight between light pigs and their heavier littermates