A team of Chinese researchers examined the use of yeast beta-glucans (YG) in broiler diets in response to a necrotic enteritis (NE) challenge. They examined how the feed supplement influenced growth performance, gut morphology, intestinal C. perfringens, endogenous antimicrobial peptide expression and humoral immune response.
“We hypothesized that yeast β-glucans supplementation could improve gut health and enhance intestinal innate immunity against NE by increasing intestinal AMPs in broiler chickens,” said the researchers in their report. “To test this hypothesis, we investigated the effect of yeast β-glucans supplementation on growth performance, gut morphology, intestinal C. perfringens population and endogenous antimicrobial peptides (β-defensins, Cathelicidins and LEAP-2) expression and humoral immune response of broiler chickens infected with Eimeria oocysts and C. perfrigens.”
The group found that the feed supplement supported gut health and promoted disease resistance in chickens facing a NE challenge.
Necrotic enteritis is a disease that causes intestinal lesions, morbidity and high mortality rates in poultry, said the researchers. In less severe cases it can result in reduced feed intake, lower body weights and diarrhea.
Such diseases are often treated with in-feed antibiotics, however concerns about creating antibiotic-resistant bacteria means there is a hunt on for replacement strategies.
“There is an urgent need to develop alternatives to antibiotics that can reduce economic losses during NE outbreaks,” said the Chinese team.
One strategy to address the disease is to use an immuno-stimulant to boost immune function, said researchers in the report. Yeast beta-glucans have been previously demonstrated to improve the immune system in mammals.
In poultry, the supplement has been shown to help protect against pathogens including Salmonella enterica, Escherichia coli and Eimeria, they said. However, little was known about how the supplement would work in chickens infected with NE.
In the experiment, 240 day-old broilers were given one of two diets including either 0 or 200mg/kg diet of YG for 42 days, said the researchers. Birds also were either control or NE-challenged.
The control diet was a corn-soybean meal pelleted diet and antibiotic and coccidiostat-free, they said. The yeast supplement was provided by Angel Yeast Company Limited.
Disease challenged birds were given a dose of Eimeria strains at day 12 and C. perfringens for three days starting day 16, they said.
Birds and feed were weighed on days 1, 12, 21 and 42, said the researchers. Body weight gain, the feed conversion ratio and feed intake were determined for each period and the entire experiment.
On day 21, two birds per group were harvested and the duodenum, jejunum and ileum were collected and checked for NE gut lesions on a 0-4 scale from none to many, they said. On days 3, 7, 14 and 21 post-infection, one bird per group was weighed and harvested for blood, jejunum and cecal samples.
Birds facing no disease challenge had the best growth performance, said the researchers.
From days 21 to 42, NE infection reduced body weight gain, tended to limit feed intake and decrease the food conversion ratio, they said. YG supplement tended to boost feed intake compared to challenged, but untreated birds.
Infected birds getting the glucan-supplement had improved body weight both for the day 21 to 42period and for the entire trial, said the researchers. They also had improved feed efficiency for the day 14-21 and 21-42 periods.
“Dietary yeast β-glucans supplementation also improved growth performance of chickens, and attenuated the retarded growth caused by C. perfringens infection,” they said. “These findings shed light for the first time on the molecular mechanisms underlying yeast β-glucans enhancement of host broiler resistance to C. perfringens infection.”
Trial-diet birds had more antibodies and lower intestinal amounts of C. perfringens and better villi height along with an improved villi height to crypt depth ratio, they said. Supplements also reduced the amount of intestinal lesions.
“YG supplementation increased gene expression of Cath-2, AvBD-4, and AvBD-10 expression at the early infection stage and Cath-1, Cath-2, and AvBD-1 at the later infection stage in the gut compared with unsupplemented birds,” said the researchers. “Decreased AvBD-10 and LEAP-2 mRNA levels were observed at the later infection stage in the glucan-supplemented birds when compared with that in the non-supplemented control group.”
The authors concluded that dietary yeast β-glucans supplementation benefited gut health of chicks challenged with C. perfringens through decreasing C. perfringens-induced NE severity, inhibiting intestinal C. perfringens growth, improving gut villi height and the V/C ratio, enhancing humoral immunity and inducing intestinal AMP gene expression.
Moreover, dietary yeast β-glucans supplementation also improved growth performance of chickens, and attenuated the retarded growth caused by C. perfringens infection. "These findings shed light for the first time on the molecular mechanisms underlying yeast β-glucans enhancement of host broiler resistance to C. perfringens infection," added the team.
Source: Animal Feed Science and Technology
Title: Effects of dietary yeast β-glucans supplementation on growth performance, gut morphology, intestinal Clostridium perfringens population and immune response of broiler chickens challenged with necrotic enteritis
Authors: X. Tian, Y. Shao, Z. Wang, Y. Guo