Feed additives

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Improving healthy post-weaning performance

Despite improvements in litter size and pre-weaning growth rates, the performance of piglets post-weaning has not increased in recent years, nor has it kept pace with genetic improvements. This article looks at how proven nutritional solutions can resolve productivity and health challenges facing producers during post weaning.

Weaning is arguably the most stressful period in the pig’s life. Gut health and hence gut health barrier function is often the result. This in turn causes leakage which paves the way for toxins and bacteria to pass via the intestinal wall to the blood and then to the organs where they can cause disease. These gut health challenges are a big issue because diseases such as PRRS, PMWS and Swine Flu are the biggest drag on performance and profit after feed cost volatility, leading to ~40% loss of revenue. Trials by Provimi (a Cargill brand) showed recently that intestinal leakage can be measured. Piglets received an oral dosage of lactulose, a sugar that they don’t normally digest or absorb so it doesn’t get into the blood unless the intestine is damaged. The consequence of damage is that it leaks into the blood and is excreted by the kidneys into urine.

Photo: Ronald Hissink
Essential oils can help overcome any post-weaning challenges.

Photo: Ronald Hissink

The amount of lactulose in this urine is used as a measure for intestinal damage; more lactulose meaning more intestinal damage. It was demonstrated in these trials that a high feed intake in piglets leads to healthier intestines that are less permeable to undesirable substances. Additional research has shown that villus height is reduced substantially in the first week after weaning. Pigs eating more feed in this period have also been shown to have higher villi in the small intestine and less intestinal damage/ better preservation of intestinal architecture (Figure 1). It seems therefore that a positive relationship exists between feed intake and villous height or villus/crypt ratio and that decreased villous heights and villus/crypt ratios may be a direct reflection of decreased feed intake in the immediate post-weaning period.

Figure 1 - Pigs eating more feed after weaning have higher villi in the small intestine (Pluske et al, 1997).


New approaches

Producers have historically tried to overcome growth performance issues and disease challenges at weaning with the use of in-feed antibiotics but growing concerns about residues in meat products and potential bacterial resistance to prophylactic, sub therapeutic and therapeutic antibiotics has led to increased research into practically feasible alternatives. Up until recently, Zinc Oxide was also used to avoid losses (financial and literal) but with tighter legislation calling for bans in certain geographies, new alternatives are needed. New strategies to improve post weaning healthy performance focus on the symbiotic relationship between nutrition and healthy performance. Leading on from the work on villi height, post weaning research has shown that high feed intake at this point in a piglet’s life can not only improve growth but also keep pathogens at bay and produce healthy pigs. Exposure to pathogens has also been shown to reduce performance, suppressing protein synthesis and stimulating muscle protein degradation. Introducing additives with proven antimicrobial and performance enhancing modes of action, like Essential Oils (EO), to the pig’s diet at this stage will help overcome any post-weaning challenges depending, of course, on blend and strength. From previous research, we can draw the conclusion that different bacteria have a varying sensitivity to different plant products. Components with phenolic structures - such as carvacrol and thymol - are highly active against test bacteria, despite their low capacity to dissolve in water. It has been suggested that they de-activate different molecules of the bacteria (such as enzymes or receptors) through their adhesion to specific sites. More studies prove efficacy on cell walls/ membranes.

Figure 2 - Trials conducted by Cargill in France (2015) show the effect of compound blends of Cinnamaldheyde, Thymol and 3 other phenols on livability, with a numerical drop of 24% in post weaning mortality.


Synergistic effects of essential oils

Carvacrol and thymol are often selected for EO blends because they have a negative effect on pathogens but little or no impact on beneficial bacteria. In an environment with high AGP and zinc, this blend also improved post weaning gain, meaning it can be used in diets with or without AGP and/or zinc. Researchers have also found that such blends improve the intestinal barrier function and reduce diarrhoea (Smith et al. 2009). In recent trials (Figure 2), liveability was seen to be considerably improved by the application of the same blend. Recent reports suggest that this kind of EO blend showed additive or synergistic effects with antibiotics and /or zinc against a range of pathogenic bacteria relevant to swine and further support gut health and performance (Figure 3). As most antibiotic classes used in animal production act both at the membrane level and inside the cell, it is likely that EO blends may facilitate their diffusion into the bacteria. In addition, it is possible that the combination of EO and antibiotics/zinc could reduce the cell’s resistance mechanisms. EO compounds have different antimicrobial spectrums, so combining the right ones together, at the right concentration/ratio, is critical to their efficacy in-vivo. They can also work synergistically with other feed additives. This effect could be explained by the fact that EO disrupt cellular membranes and facilitate the diffusion of organic acids into the bacteria.

Figure 3 - European trials conducted  recently by Cargill 5% average daily gains in an antibiotic and /or zinc environment using compound blends of Cinnamaldheyde, Thymol and 3 other phenols.



We have seen that nutritional management strategies can have a profound impact on the feed intake, physical performance and overall health of post weaned piglets. It has also been shown that additives such as EO can provide an alternative to antibiotics. However, it is necessary to select the right nutritional solution. For example, characteristics such as the type, number, concentration and stability of EO components will all play a determinant role in the bio-efficacy of the chosen solution. Likewise, the ability to get enhanced results through the addition of organic acids and probiotics to EO will give the producer a competitive advantage.

References are available on request.

Mickael Perpoil


  • Fernando Bravo de Laguna

    Hi. I am ellaborating a desk study about the synergistic effects of probiotics and essential oils. Is it posible to get recent references? Thanks in advance.

  • Emmy Koeleman

    Dear Fernando, could you please send me an email? so I can forward the references. emmy.koeleman@proagrica.com

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