High doses of ZnO have commonly been used in the diets of weaned piglets for reducing post-weaning diarrhea, supporting immunity and improving performance. To achieve such effects, ZnO has been added at doses ranging from 2,000 to 4,000 mg/kg diet while the nutritional zinc requirement for piglets is only 80 –100mg/kg. This medicinal use of ZnO has caused environmental problems and it has also been associated with increased antimicrobial resistance.

For these reasons, the therapeutic use of ZnO will be banned in EU and from June 26th 2022 zinc can only be supplied in quantities that meet the nutritional requirements of piglets. Hence, there’s a need for finding other means to reduce post-weaning diarrhea and improve performance of piglets. The ability of resin acids to reduce the inflammation-induced degradation of connective tissues in the intestine and to balance the composition of intestinal microbiota make Progres® a potential ingredient for the replacement of medicinal ZnO.

A trial at the Faculty of Veterinary Medicine, University of Helsinki, demonstrated that Progres® addition in the feed reduced diarrhea incidence and improved growth of post-weaned piglets. It was estimated that the seen benefits were caused by the reduced inflammation and positive modulation of microbiota in the intestine. The following text is based on the scientific article by Uddin et al. 2021 in Animals and it summarizes the main results of the trial in piglets.

Materials and methods

The purpose of the trial was to determine the effects of resin acids (Progres®) supplementation on sow and piglet performance and incidence of post-weaning diarrhea. 40 sows (Yorkshire × Landrace) were selected based on body condition and parity and allocated to Control (C) and Progres® (P) treatments (figure 1). Sows in the test treatment (P) received Progres®, 1.5 kg/ton of feed in their diet from six weeks before the expected date of farrowing until weaning at four weeks.  Litters from both sow feeding treatments were allocated to Control and Progres® creep feed treatments (n=10) creating treatments PP, PV, CP and CC. At weaning, piglets were again allocated to Progres® (P) or Control (C) weaning feed treatments creating eight different treatments. Progres® inclusion in the piglet diets was 1.0 kg/ton and the trial continued until the piglets were seven weeks of age.

Figure 1. Dietary treatments in the trial

Piglets were individually weighed at birth, 24 hours after birth, at weaning (28 days) and three weeks post-weaning. Piglet mortality and incidence of diarrhea pre- and post-weaning were recorded. Fecal samples were collected from six piglets per litter at 4 and 7 weeks of age to study the effect of dietary treatments on intestinal microbiota and concentration of myeloperoxidase, a biomarker of intestinal inflammation.

Results and discussion

The incidence of post-weaning diarrhea was significantly lower (–40,7 %) in piglets that received Progres® in their weaner diet (PPP, PCP, CPP and CCP) than in piglets receiving control diet post-weaning (figure 2a).  A numerically lower post-weaning mortality (–52,4 %) was recorded in piglets that received Progres® in their weaner diet (figure 2b).

Figure 2. a) Post-weaning diarrhea incidence % of piglets b) Piglet mortality % post-weaning

The weaning weights and the diarrhea incidence and mortality during the suckling period did not differ between the dietary treatments. However, piglets from the Progres® fed sows that received it also in creep and weaning feed were 1.6 kg heavier (p <0.05) at 7 weeks of age than piglets from the control (CCC) group. The fecal concentration of the inflammation biomarker myeloperoxidase (MPO) at seven weeks was lower in piglets that received Progres® in their weaner diet (figure 3). Progres® supplementation also significantly increased the numbers of butyrate producing Lachnospiraceae and Ruminococcaceae bacteria and reduced the numbers of opportunistic pathogens, such as  Bacteroidetes, Streptococcaceae, and Desulfovibrionaceae in feces (results not shown here).

Figure 3. The concentration of myeloperoxidase (MPO) in feces at 7 weeks

Progres® supplementation in the weaner diet reduced the incidence of diarrhea and decreased mortality compared to the control. It also improved the growth of the piglets post-weaning. The resin acids of Progres® have been previously shown to reduce the degradation of collagen and infiltration of inflammatory T- cells in the intestinal tissues of broilers. In this study, Progres® reduced the concentration of inflammation biomarker myeloperoxidase in feces. Thus, the anti-inflammatory action of Progres® may explain the effects on post-weaning diarrhea, mortality and growth. The observed effects on intestinal microbiota with increased numbers of beneficial butyrate-producing bacteria and reduced numbers of opportunistic pathogens may also have contributed to the performance results.


In conclusion, supplementing the diet with Progres® reduced diarrhea incidence by 40 % and mortality by over 50 % in weaned piglets, simultaneously improving their growth performance. Reduced intestinal inflammation and beneficial modulation of intestinal microbiota were the probable reasons for the improved performance. Altogether the results demonstrated beneficial effects of Progres® in piglets and its potential to replace high doses of ZnO in piglet feeding.


Uddin, M.K., Hasan, S., Mahmud, M.R., Peltoniemi, O. and Oliviero, C. (2021) In-feed supplementation of resin acid-Eeriched composition modulates gut microbiota, improves growth performance, and reduces post-weaning diarrhea and gut inflammation in piglets. Animals 11: 2511.