What Happens After Weaning? A Closer Look at Piglet Growth

Weaning weight is an important measure of piglet performance. But when assessing an early-life nutritional intervention, it is worth asking a second question: what happens to those pigs after weaning? 

Heavier piglets at weaning generally perform better later in life, but that does not mean every strategy that adds weight before weaning produces the same long-term result.

Indeed, the key is not only how much a piglet weighs at weaning, but also the physiological condition in which it reaches the transition and the growth trajectory that follows.

Weaning weight is one of the most useful and familiar performance indicators in pig production. Since heavier pigs at weaning generally tend to grow faster afterwards and reach market weight sooner, it is logical that producers, veterinarians and nutritionists pay close attention to this number.

However, a piglet can be heavier at weaning for several different reasons. It may simply have consumed more energy, it may have had greater access to milk or creep feed, or an intervention may have affected intestinal development, nutrient utilisation or adaptation to the coming weaning challenge. This distinction matters because an early weight advantage does not always persist.

Higher Weaning Weight Doesn’t Always Mean Better Performance

A 2024 Teagasc study compared several pre-weaning feeding strategies, including dry starter feed and liquid milk replacer. At day 27, mean piglet weight increased from 7.87 kg in controls to 8.10 kg with dry starter and 8.27 kg with liquid milk replacer.

However, the authors found no residual treatment effect on body weight after weaning or at slaughter. The post-weaning phase was weight-balanced within treatment, so the study should not be read as a direct demonstration of the original weight gap physically disappearing, but it does show that a pre-weaning treatment effect on body weight did not necessarily translate into a later treatment effect.

A 2023 systematic review and meta-analysis reached a similar broader conclusion: responses to creep feeding were variable. Across the publications included, 46% reported an improvement in pre-weaning performance and 58% reported improved nursery performance.

The practical message is not that weaning weight is unimportant. It is that additional weight at weaning and a change in subsequent growth trajectory are related, but they are not necessarily the same outcome.

Beyond Weaning Weight: What Condition Is the Piglet in at Weaning?

This is where the concept of micro-enteral nutrition becomes relevant.

Rather than trying to provide a substantial quantity of calories, the micro-enteral nutrition approach developed by Tonisity is designed to deliver small amounts of specific nutrients directly to the gastrointestinal tract during critical early-life periods.

A 2025 peer-reviewed study by Gong and colleagues evaluated 160 piglets receiving the nutritional solution from days 2 to 8 and again during the three days before weaning.

By day 24, treated piglets were 250 g heavier than controls, 7.20 versus 6.95 kg, with a significant difference.

The important point is that the additional energy supplied by the solution was very small, only about 2.4 kcal per piglet per day. On a caloric basis alone, this cannot plausibly account for the observed difference in body weight.

In this research, the authors also measured changes at the intestinal level.

Jejunal villus height was about 8% greater, and the villus-to-crypt ratio was about 31% higher. GLP-2 expression was 3.35 times higher, while expression of the tight-junction markers ZO-1 and Claudin-1 increased by 64% and 56%, respectively. Changes were also observed in immunoglobulin levels and in specific microbial populations.

Although these measurements do not prove that a particular intestinal change causes a specific finishing-weight advantage months later, they show that the treatment response is not limited to extra grams on the scale, but that treated piglets are physiologically different.

What Happens Immediately After Weaning?

A commercial-farm study led by Vinícius de Souza Cantarelli at the Federal University of Lavras in Brazil provides a particularly useful link between pre-weaning intervention, intestinal measurements and post-weaning performance.

The study involved 120 litters and compared four treatment strategies, including a full programme combining days 2 to 8 with peri-weaning administration.

In the full-programme group, the numerical weight advantage at weaning was not statistically significant: 7.45 kg versus 7.03 kg in controls.

Seven days after weaning, however, the difference had increased to 8.10 versus 7.44 kg, a 0.6 kg advantage, with P=0.009.

By day 14 post-weaning, the difference was 0.86 kg (10.17 versus 9.31), with P=0.020. Average daily gain over the first 14 days post-weaning was 196 g/day versus 161.

Post-Weaning Performance and Intestinal Morphology

The same study also found differences in intestinal morphology after weaning.

Villus length was 256 micrometres in the full-programme group compared with 189 micrometres in controls, while the villus-to-crypt ratio was 1.02 versus 0.76.

These results are valuable because performance and intestinal morphology were evaluated within the same experiment and during the same transition period.

Again, the correct interpretation is not that longer villi alone explain every gram of subsequent growth. The stronger point is that the performance response after weaning occurred alongside measurable differences in intestinal condition.

If the question is whether early-life nutrition matters beyond the nursery, the most informative studies are those that follow pigs for much longer, and two commercial trials provide useful examples.

US Study 18-014-P-P: Birth to Finishing

In this trial, 3,862 piglets from 353 litters were enrolled and it was possible to follow 2,193 pigs up to the end of the finisher stage.

There was no weight advantage at weaning (6.13 kg in the Tonisity group versus 6.18 kg in controls, P=0.52). At the end of nursery, the numerical advantage was 0.41 kg, with a P value of 0.10. However, at 168 days of age, treated pigs were 3.04 kg heavier, and that advantage was significant (P=0.002).

This is an important observation because the later difference cannot simply be described as the preservation of extra weight already present on weaning day.

Poland Study 17-031-P-R: Weaning to Market Weight

In the Polish study 17-031-P-R, piglets receiving Tonisity Px before weaning were 0.31 kg heavier at weaning and 1.70 kg heavier at the end of nursery. Pigs were marketed at approximately 120 kg, and pens that had received Tonisity Px pre-weaning reached this target around seven days earlier than controls. Feed conversion during the fattening/finishing period was also lower, at 2.74 compared to 2.79 for the control. This 1.8% better FCR (P = 0.0187) means that approximately 5% less feed was consumed during the finishing stage for the same amount of growth.

The study did not investigate the physiological basis for the later performance response. However, the increase in the weight difference from 0.31 kg at weaning to 1.70 kg at the end of nursery, together with the earlier achievement of market weight, indicates that the later advantage was not simply the result of carrying forward the initial difference in weaning weight. 

What Does the Wider Tonisity Dataset Show?

Individual trials show what happened under specific farm conditions. The broader dataset provides a better indication of how consistently the weight response has been observed across different farms and production systems.

Tonisity’s 2026 weight meta-analysis includes 46 studies and 41,983 pigs with weaning measurements. The average difference at weaning was +300 g.

Of these studies, 12 followed 15,242 pigs through to the end of nursery, with an average weight difference of +1.14 kg. Four studies, involving 4,080 pigs, continued through to finishing, where the average difference was +2.50 kg at the same age.

The nursery and finishing results come from subsets of the original 46 studies and should therefore not be interpreted as a progression from +300 g at weaning to +2.50 kg at finishing in the same population. Weight differences were observed at weaning, at the end of nursery and at finishing.

Assessing Early-Life Nutrition in Piglets

The effect of an early-life nutritional intervention can be assessed at three levels: weight at weaning, physiological condition at weaning, and subsequent growth performance.

Weaning weight provides an immediate measure of growth during the pre-weaning period. Other measurements, including intestinal morphology, barrier function and immune parameters, can provide information on the physiological condition of the piglet at weaning. Follow-up measurements during nursery and finishing show whether any effect remains after supplementation has ended.

Weaning weight is therefore an important KPI, but it does not provide a complete assessment of the response. Similar weaning weights can be associated with different physiological conditions, while differences in later performance may occur even when the weight difference at weaning is small or absent.

Assessment should therefore consider both the immediate response at weaning and the subsequent performance of the pigs through nursery and finishing.

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Frequently Asked Questions About Weaning Weight and Piglet Performance

Does higher weaning weight always lead to better post-weaning performance?

Not necessarily. Heavier pigs at weaning generally tend to perform better later, but an increase in weaning weight resulting from a specific intervention does not necessarily translate into a later treatment effect. Evidence from pre-weaning feeding studies shows that additional weight at weaning and subsequent growth trajectory are related, but they are not necessarily the same outcome.

Why is weaning weight not enough to assess an early-life nutritional intervention?

weight is an important KPI, but it represents only one point on the piglet’s growth curve. A more complete assessment considers weight at weaning, physiological condition at weaning and the growth trajectory that follows.

What physiological factors can be considered alongside piglet weaning weight?

Intestinal morphology, barrier function, immune status and adaptation can provide additional information about the piglet’s condition at weaning. In the 2025 study by Gong and colleagues, differences in body weight occurred alongside measurable changes in jejunal villus height, villus-to-crypt ratio, GLP-2 expression, tight-junction markers, immunoglobulins and specific microbial populations.

Can early-life nutrition affect pig performance after weaning?

Studies included in the article show performance differences after weaning. In the Cantarelli/UFLA study, for example, the full-programme group was not significantly different in weight at weaning, but differences were observed at seven and 14 days post-weaning. Commercial longitudinal studies also reported differences later in nursery and finishing.

References

1. Arnaud EA et al. Translational Animal Science. 2024. Pre-weaning feeding strategies and subsequent pig performance.

2. Muro BBD et al. Animals. 2023. Systematic review and meta-analysis of creep-feeding responses in piglets.

3. Gong C, Hao Z, Liao X, Collier RJ, Xiao Y, Zhao Y, Chen X. Veterinary Sciences. 2025;12:715. Isotonic Protein Solution Supplementation Enhances Growth Performance, Intestinal Immunity, and Beneficial Microbiota in Suckling Piglets.

4. Cantarelli VS et al. Federal University of Lavras (UFLA), Brazil. 2018. The Use of Isotonic Supplement in Piglets as Preparation for Weaning. Study 18-126-P-R.

5. Tonisity Study 18-014-P-P. USA. Commercial longitudinal study from birth to finishing.

6. Tonisity Study 17-031-P-R. Poland. Effects of Tonisity Px on Time to Finishing.

7. Tonisity 2026.03 Weight Meta-Analysis. 46 studies at weaning; 12 continued to end nursery; 4 continued to finishing.