Thymol, carvacrol supplements may boost broiler growth, gut health

Enzymes and thyme oil may grow bigger, healthier broilers © iStock.com

When used with a wheat-based diet, thymol and carvacrol (T+C) supplements may boost broiler growth and gut health. 

The supplements also can be used effectively with enzymes (E) that break down non-starch polysaccharides (NSP) an international team of researchers reported in Animal Feed Science and Technology​.

Goals of the research included developing a better understanding the interaction between a phytogenic supplement, with or without a NSP-degrading enzyme, and bird performance, nutrient uptake and gastrointestinal health in broilers fed a wheat-based diet, they said.

“The present study showed that thymol + carvacrol, in combination or not with an NSP-degrading enzyme, improved growth performance, enhanced nutrients retention, increased total VFA [volatile fatty acid], reduced cholesterol and modulated intestinal microbial counts in broilers fed on a wheat-based diet,”​ said researchers.

Why T+C supplements​

Wheat is often used in diets but it has more anti-nutritional factors than some feeds, said researchers. It also contains NSP, which can negatively influence digesta viscosity and allow for pathogenic bacteria including Escherichia coli​ and Clostridium perfringens.​

While enzyme use can benefit the diet, there is renewed interest in finding non-antibiotic treatments that can also improve broiler growth, they said. These include use of phytogenic additives, which also may improve bird health.

“Thymol and carvacrol, the main bioactive components in thyme essential oil, are appetite- and digestion-stimulating, and have considerable antimicrobial and antifungal activity, which have been reported to promote the growth of beneficial bacteria and inhibits the growth of potentially deleterious intestinal bacteria,” ​said researchers. “Given their antimicrobial activity, it would be expected that thymol and carvacrol could have positive effects on growth and performance in broilers.”​

Additionally, the supplements are recognized as safe by the US Food and Drug Administration and according to EU legislation, they said.

Experiment details​

The 42-day experiment examined six different diets, said the scientists. The diets included three separate levels of T+C, 0, 100mg/kg of diet and 200mg/kg, and two levels of enzyme, 0 or 0.5g/kg of diet.

The diets were given to 30 groups of 12 birds, replicated five times and carried through starter, grower and finisher diets, they said. check

Feed eaten and body weight were measured on days 0, 10, 24 and 42 and average daily feed intake (ADFI), average daily gain (ADG) and the feed efficiency ratio (G:F) were determined for those periods, they said.

On day 24, the small intestines were harvested from two birds per replicate and on day 42 internal organs were compared, they said. Excrement and cecal contents were collected from birds in each group. CHECK

Blood samples were taken and examined for values including total cholesterol, total protein and triglycerides, they said.

Results ​

Birds getting diets containing either the enzyme or the T+C supplement had a higher body weight, average daily gain and improved feed efficiency at day 42, said the researchers.

“The present study showed that the phytogenic product thymol + carvacrol, and NSP-degrading enzyme independently improved growth performance, enhanced nutrients retention, increased total VFA, reduced cholesterol and modulated intestinal microbial counts in broilers fed on a wheat-based diet,” ​they said. “These results have both productive and health implications for the broiler industry and warrant further investigation.”

Birds getting a diet including the enzyme had reduced digesta viscosity in the small intestine, they said. And those getting the supplement had the viscosity reduced in the jejunum and ileum at day 24.

“E or T+C treated birds showed an increased retention of DM, protein and energy,” ​they said.” Dietary supplementation with E and T+C increased total VFA and acetate levels at d 24 and 42, whereas the level of butyrate decreased.”​

Broilers treated with the enzyme or T+C at 200mg had lower amounts of harmful bacteria and more Lactobacilli ​than control birds, they said. Treatments also improve ADG by 9.9%, enzyme, and 11.3%, supplement.

“E supplementation increased serum triglyceride, total cholesterol, total protein (TP), albumin and globulin concentrations, while T+C supplementation decreased total cholesterol, TP and albumin at d 4,” ​said researchers. “E supplementation decreased the relative length of duodenum, jejunum and ileum of broilers.”​

Relative weights for the carcass, liver and pancreas were decreased when the enzyme was used, they said. Relative carcass weight also altered for birds getting the supplement.