Resin acids for piglets, in comparison with zinc oxide (presentation at EAAP2021)

Year 2022 will witness the withdrawal of pharmacological doses of zinc oxide from piglet feeds in the European Union. Prophylactic use of 2500–3000 ppm of zinc oxide in piglet diets is an efficient means of reducing post weaning diarrhoea (PWD), but the accumulation of this heavy metal into the environment, as well as its contribution to antimicrobial resistance issues, has been seen as unacceptable by the EU.  

At the intestinal level, PWD causes an inflammatory response with bacterial overgrowth, dysbiosis and diarrhoea. In severe cases, systemic inflammation with fever results from the leakage of lipopolysaccharide (LPS), a molecule derived from the outer wall of Gram-negative bacteria, into blood circulation. The physiological process involves the activation of an array of interleukins and other cytokines which are mediators of systemic pro-inflammatory and anti-inflammatory responses. Reduced growth performance and increased mortality are common consequences of severe PWD in piglets.

When the medical use of zinc oxide is banned, the obvious challenge of the pig industry is to reduce the incidence of PWD by other prophylactic means. Coniferous resin acids are natural molecules with antimicrobial and anti-inflammatory activity. In a recent publication by Uddin et al. (2021), a resin acid-based product reduced gut inflammation and PWD in piglets, and thereby also improving piglet performance.

On the first of September, the 72^nd annual meeting of the European Federation of Animal Science, EAAP2021, hosted a session titled “Good health of pigs and poultry: increasing robustness through feeding and management”. Appropriate to the topic, Dr. Xiaonan Guan from Schothorst Feed Research gave a presentation called “Effect of dietary resin acid and zinc oxide in weaned piglets subjected to an immune challenge”, co-authored by H. Kettunen, R. Santos, J. Vuorenmaa and F. Molist.

In this study, 48 piglets with a mean weight of 7.5 kg were allocated to one of the four treatment groups: non-challenged control (phosphate-buffered saline, PBS), a challenged control (LPS) and 2 challenged groups with dietary treatments of 2500 mg ZnO (LPS + ZnO) and 200 mg/kg of RAC (LPS + resin acid concentrate, RAC). On days 7 and 21, the piglets were subjected to LPS or PBS injections, the LPS-treatments thus modelling the LPS-related systemic effect of PWD. The development of cytokine response was monitored from blood samples taken at a time series after each LPS-challenge.

The treatments did not affect the weight gain of piglets during the experiment, which is not surprising due to only 12 replicate piglets per group. Rectal temperature measurements proved that the LPS-challenge was effective in stimulating the inflammatory response, compared to the nonchallenged control pigs. Cytokine profiles of the blood samples suggested immunomodulatory effects for both ZnO and RAC-treatments. It is noteworthy that the levels of the anti-inflammatory IL-10 -cytokine were highest in the RAC-treatment.

According to the authors, RAC may boost the immune response of piglets without penalizing growth performance during a LPS challenge, but a larger number of animals would be needed for a final conclusion. The study has been submitted to a peer-reviewed scientific journal for publication.

Uddin et al. (2021) In-Feed Supplementation of Resin Acid-Enriched Composition Modulates Gut Microbiota, Improves Growth Performance, and Reduces Post-Weaning Diarrhea and Gut Inflammation in Piglets. Animals 11:2511. https://doi.org/10.3390/ani11092511