Special Edition: Gut health and immunity

Team identifies effective alternatives to in-feed AGPs for piglets

By Jane Byrne

- Last updated on GMT

GettyImages/Davy3 Photo
GettyImages/Davy3 Photo

Related tags Antibiotic organic acids essential oils probiotics

Chinese researchers have found supplementation of benzoic acid, Bacillus coagulans and oregano oil combined has the potential to improve the immune status, intestinal barrier integrity and microflora of piglets on antibiotic free diets.

The study was published in the journal, Animal Nutrition​.

Benzoic acid, Bacillus coagulans and oregano oil play an important role in stabilizing the intestinal ecosystem of animals, including increasing the number of health-promoting bacterial species (such as Lactobacilli, Bacillus and Bifidobacteria) and decreasing the number of potential pathogenic bacterial species (such as E. coli) (Diao et al., 2014, Lin et al., 2011, Zou et al., 2016).

“Our results demonstrated that dietary benzoic acid, Bacillus coagulans and oregano oil combined supplementation can improve intestinal microecological balance, which was evidenced by the improvement in Bifidobacterium or Bacillus populations, and the decrease in the E. coli population of cecal digesta.”

Benzoic acid and Bacillus coagulans combined supplementation, they said, improved the intestinal microflora, and, in this way, could boost growth performance of weaned piglets.

“Intestinal microflora is crucial for maturation of the immune system and development of normal intestinal morphology. Konstantinov et al. (2006) indicated that a healthy and stable microflora prevents the development of intestinal diseases and results in improved performance.”


In recent years, organic acids, probiotics and essential oils combined supplementation in animal diets have attracted wide research interest due to their potential ‘synergistic’ and ‘additive’ benefits on growth performance (Basmacioglumalayoglu et al., 2016, Giannenas et al., 2016), said the authors.

Based on their positive effects, benzoic acid, Bacillus coagulans and oregano oils are considered to be good potential alternatives for in-feed antibiotic growth promoters, they reported.

“However, the experimental results of these additives have varied widely and the effect of a single additive is limited.”

The team cited previous studies indicating that organic acids could improve growth performance and has antibacterial action primarily via decreasing pH values of the stomach and gut digesta, modulating microbial population, improving nutrients digestion, and other possible mechanisms (Mroz, 2005).

Benzoic acid, as a kind of organic acid, was authorized to be used in pigs at the dose of 0.5% to 1.0% in the EU in 2003, noted the Chinese team, adding that previous studies have indicated that benzoic acid could improve growth performance and nutrient digestibility, and maintain intestinal microflora balance of weaned piglets (Guggenbuhl et al., 2007).

Bacillus coagulans, as a kind of probiotic, not only has all the characteristics of lactic acid bacteria, but also has strong resistance to acid, high temperature, high pressure, and easy storage properties (Cavazzoni et al., 1998), they said.

“Previous studies reported that Bacillus coagulans could improve growth performance, maintain intestinal microflora balance and improve immune response of animals (Zhou et al., 2010, Hung et al., 2012).”

Oregano oils, which are essential oils obtained from oregano plant by a steam distillation process, are comprised of more than 20 ingredients; of these ingredients, carvacrol and thymol are the most abundant (Vokou et al., 1993), commented the researchers.

“It has been demonstrated that oregano oil could improve growth performance by improving antioxidant capacity and decreasing the number of pathogenic bacteria in the gut of pigs (Botsoglou et al., 2002, Zheng et al., 2009).”


However, little information is available on the effects of benzoic acid, Bacillus coagulans and oregano oils combined supplementation on growth performance, immune status and intestinal health of weaned piglets.

Therefore, the Chinese team said their goal was to carry out a study to investigate the effects of those products on growth performance, immune status and intestinal barrier integrity of piglets.


The Chinese team said they purchased benzoic acid from DSM (China). Bacillus coagulans was provided by the Sanzheng Group at a density of 5 × 109 CFU/g, while oregano oil as a free-flowing powder, was provided by Kemin Industries. The major active components in the oregano oil were carvacrol and thymol - a minimum of 22 g/kg carvacrol and a minimum of 11 g/kg thymol.

Defatted rice bran and silica were used as carriers, they added.

The researchers outlined how, during their 26-day experiment, 25 piglets were randomly assigned to 5 treatments:

  • A basal diet, negative control (NC)
  • NC added with antibiotics, positive control (PC)
  • NC added with benzoic acid at 3,000 g/t and Bacillus coagulans at 400 g/t (AB)
  • NC added with benzoic acid at 3,000 g/t and oregano oil at 400 g/t (AO)
  • NC added with 3,000 g/t benzoic acid and Bacillus coagulans at 400 g/t and oregano oil at 400 g/t (ABO)

The basal diet was formulated to meet or exceed the nutrient requirements recommended by the National Research Council (NRC, 2012) and all pigs had ad libitum access to feed and water.

On day 27, all piglets were euthanized to obtain jejunal mucosa to measure immune status and intestinal barrier integrity, they explained.


The team said their results showed that pigs fed AB diet increased the final body weight and average daily body weight gain and decreased the ratio of feed to gain compared with the NC group.

In comparison with the NC group, they saw that AB, AO and ABO decreased serum tumor necrosis factor-α concentration and ABO decreased interleukin-1β concentration in serum and jejunal mucosa.

When compared with the NC group, the team observed that AB up-regulated mRNA expressions of sodium-glucose cotransporte1, claudin-1, occludin and mucin2 in jejunal mucosa and the populations of Bifidobacterium and Bacillus in cecal digesta.

Finally, compared with the NC group, the researchers reported that ABO increased jejunal mucosal occludin mRNA abundance and Bifidobacterium population in cecal digesta, and decreased Escherichia coli population in cecal digesta. Furthermore, AB and ABO increased the Bacillus population in the cecal digesta compared with the PC group, they said.

In concluding, the team said their findings indicate that dietary benzoic acid and Bacillus​ coagulans combined supplementation significantly increased ADG and decreased F:G of weaned piglets.

This may be due to the better gut characteristics including increased nutrient digestibility, healthy and stable intestinal microflora, and better intestinal barrier integrity.

They also showed that dietary AB increased the mRNA abundance of SGLT1 in jejunal mucosa of piglets, thus resulting in the better nutrient absorption relative to piglets fed NC diet.

“The result is consistent with the improvement of growth performance in AB group. This may be associated with the changes in the intestinal barrier integrity.”

They said the research also demonstrated that ABO could ameliorate the weaning-associated intestinal damage.

“These results indicated that dietary ABO may improve intestinal integrity partially by reducing pro-inflammatory stimulus, rather than enhancing the anti-inflammatory response.”

Source: Animal Nutrition

DOI: https://doi.org/10.1016/j.aninu.2020.02.004

Title: Effects of benzoic acid, Bacillus coagulans and oregano oil combined supplementation on growth performance, immune status and intestinal barrier integrity of weaned piglets

Authors: Yu et al

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