Over the years, genetic selection has resulted in a substantially increased number of piglets born per sow in each litter worldwide. This increase in litter size often means smaller and more vul¬nerable piglets, with greater variation within litters. At the same time, when sows deliver large litters, their milk does not increase in proportion to the increased number of piglets born and thus the piglets suffer from a milk shortage. As a result, it is becoming increasingly common practice to provide suckling piglets with feeds to supplement sow milk.
This article examines the relevance of early supplemental feed¬ing to supporting piglets' growth and development.
Surveys of sows
In a recent survey of 224 sow farmers in Belgium carried out by Ghent University, approximately 50% of the farmers had experienced issues with the number of piglets exceeding the number of functional teats on a sow (i.e. supernumerous pig¬lets). In total, 90% of these farmers indicated that they used dry or gruel feed and 49% used supplemental milk to alleviate the issues related to supernumerous and small piglets. Work recently conducted in the Netherlands yielded similar results, with the proportion of farms using a milk supplement increasing from 49% in 2014 to 54% in 2015. In this respect, the market in Belgium, the Netherlands and Luxembourg (Benelux) seems to be taking the lead.
Supplemental feeds aid 'catch-up'
Data generated recently supports the view that it is worth¬while supporting the less fortunate piglets in large litters dur¬ing the first weeks in life. For example, when analysing a data set of over 60,000 piglets born at three experimental stations, we concluded that not only birth weight, but also weaning weight and the body weight two weeks post-weaning are important determinants for body weight at the end of the nursery phase. This concurs with data from other groups that extended this observation up to slaughter weight. Moreover, our analysis showed that lighter piglets can catch up with their heavier peers because they seem to have the ability to effi¬ciently digest nutrients and grow like their heavier littermates.
Importance of early feed intake
Typically, supplemental feed intake is relatively steady up to two weeks of age and increases, first gradually then sharply, up to weaning. This pattern coincides with the gap between milk production and the nutrient requirements of the fast-growing litter in the later phases of lactation.
From studies conducted at the Swine Research Centre in St Anthonis, the Netherlands, intakes were observed that vary between 0 and over 1 kg of dry matter per piglet over a 24-day lactation period, with 400 g being a good average. The level of intake is influenced not only by litter size, but also by lactation length, milk production and ambient temperature. Milk production, in fact, depends on temperature: a sow under heat stress will have a reduced milk output, forcing her litter to find addi¬tional sources of nutrition.
Contrary to general belief, birth weight has only a limited influence on the supplemental feed intake of piglets. Our observations showed that the average birth weight of 'eaters' is similar to that of 'non-eaters' and that, in both categories, piglets that are very light (<1 kg) and heavy (>2 kg) are repre¬sented. Supplemental feeding can, but not always, affect body weight development until weanling. In general, however, post-wean¬ing performance and health will be promoted. Also, especial¬ly with longer lactations, one might observe that sows are better able to maintain body condition. Sometimes effects are more subtle, as will be explained below.
A closer look at the gut
To explain how relatively low levels of supplemental feeding affect post-weaning performance, a study was conducted into pre-weaning gut development. The hypothesis was that creep feed represents energy provision and – by its specific compo¬sition – induces the secretion of gut hormones that modulate intestinal development. So a group of piglets was studied that consumed a highly nutrient dense, complex milk replacer (i.e. Milkiwean Yoghurt).
By contrast, the control piglets had no access to supplemental feed and solely relied on sow milk. The piglets were from very prolific sows (at least 13.5 piglets) of similar parities (3.6 ± 0.8). On day 21, these piglets' body weight and gut development was assessed. Supplemental milk consumption was close to 70 g of dry matter per piglet per day and weight gain was 20% more (310 vs 255 g/day) in the milk-fed piglets during the week prior to post-mortem analysis.
Close to 90% of the piglets consumed the supplement, which underlines the desire of piglets in current production systems to have access to supplemental nutrition, in addition to sow milk. Besides the fact that the pigs fed a milk replacer were about half a kilo heavier, litters were also more homogeneous than the control group. Moreover, the small intestine of the piglets was heavier than that of the control animals, both in absolute terms and when expressed as a percentage of their body weight. Also, the gut of these animals showed signs of higher cell proliferation, i.e. increased crypt depths and PCNA (a marker for cell proliferation). Furthermore, other indices for gut development and gut function were more favourable in piglets fed the milk replacer. Moreover, the animals fed a milk replacer had higher concentrations of fermentation products (e.g. butyrate) in the large intestine, indicating a higher micro¬bial activity. It is conceivable that all these changes in milk-fed piglets lead to a better response to the weaning transition owing to an increased capacity for the uptake of nutrients.
Importance of supplemental feeding
Larger litters mean the need for proper supplemental feeding is increasingly important. Providing supplemental milk and creep feed does not necessarily lead to a higher weaning weight, especially when weaning occurs at an early age. The main benefit arises from a better developed gut at weaning and enhanced post-weaning performance. It is therefore important to encourage farrowing room staff to stimulate feed intake by providing palatable and well-balanced diets via diligent feeding management.