Supplementation of Broiler Diets with Intrinsically Heat Stable Xylanase to Increase Growth Performance and Promote Gut Health of Broiler Chickens

Xylans, together with β-glucans and cellulose constitute non-starch polysaccharides (NSP) that cannot be fully degraded by monogastric animals (Cowieson at al., 2008). NSPs have an antinutritive effect by increasing the viscosity of the intestinal digesta (Choct and Annison, 1992; Craig et al., 2020). This increase in digesta viscosity causes an impairment of nutrient bioavailability and a decrease in metabolizable energy, lowering the overall performance of animals (Bedford and Morgan, 1996). Poultry do not produce endogenous carbohydrases capable of hydrolysing the pentosan NSPs, such as the arabinoxylans, present in cereals. Addition of enzymes such as xylanases, β-glucanases, and cellulases to the feed reduce the antinutritional effect of NSPs. It is believed that these enzymes degrade polysaccharide cage structures around proteins and reduce the viscosity of the intestinal contents of the animals. Therefore, enzymes are widely used in animal nutrition, especially for poultry and pigs, for more complete utilization of feed components originating from plants. Supplementing feed with xylanases has been shown to improve nutrient digestibility and help maintain good gut health (Walsh et al., 1993; Singh et al., 2012; Craig et al., 2020). In this study we investigated the dose-related effect of supplementation of an intrinsically heat stable xylanase on performance and gut health of broilers fed with a corn-soy broiler diet.

A total of 1,000 broiler chickens (Ross 308) were allocated to five dietary treatments comprising 10 pens each (20 chickens per pen) for 1 to 35 d of age. The treatments were: standard corn soybean diet (PC), diet with 100 kcal/kg reduction in metabolizable energy and 2% reduction in crude protein and digestible amino acids (NC), NC with 10g/T of xylanase (T1), NC with 15g/T of xylanase (T2) and NC with 30g/T of xylanase (T3). The feed was pelleted at 80°C for 30 seconds. The activity of xylanase recovered after pelleting was greater than 80%.

Bird weight and feed intake were measured on a pen basis up to 35 days. Caeca of 36 broilers were collected at 35 d for the quantitative analysis of microflora. Lactobacillus spp. and Escherichia coli enumerations were done on MacConkey agar and eosin methylene blue agar, respectively. Intestinal segments (duodenum, jejunum and ileum) were collected from 36 broilers at the end of the experiment to determine intestinal morphology. Tissue samples were washed then fixed in 10% formaldehyde solution. The villus length (VH) was defined from the villus tip to the villus-crypt junction between each villus, while the crypt depth (CD) was measured from the top to the bottom of villi between adjacent villi and the villus width. Caecal digesta samples from 6 birds in each treatment were collected at the end of the experiment for the measurement of volatile fatty acid (VFAs) content. VFAs were quantified according to Apajalahti et al. (2019).

The effect of dietary treatments on performance parameters of broilers in the present study was analyzed with one-way ANOVA using SAS 9.0. The GLM procedure was used to quantify significant difference among treatments for all measurement by Duncan’s new multiple range test. The average values including the standard error of the mean were calculated for every examined parameter. The level of significance was set at P< 0.05.

Table 1 - Main ingredients of the basal diets for each growing phase

A dose response was observed for body weight and feed conversion ratio (Table 2) after 35 days with 10 g/T xylanase and 15 g/T able to compensate the down specifications in term of growth performances and 30g/T yielding a statistically significant difference compared with 10 g/T for both body weight and FCR.

Table 2 - Body weight at Day 35 and FCR over 35 days.

The study also showed the effect of xylanase on the gut. Caecal samples were collected and Lactobacillus spp and Escherichia coli were counted (Table 3). Counts of Lactobacillus spp tended to increase with the addition of 10g/T and 15g/T and the change was statistically significant at 30g/T. The opposite effect was observed for Escherichia coli with a count decrease observed upon xylanase supplementation (Table 3).

Table 3 - Body weight at Day 35 and FCR over 35 days.

Caecal volatile fatty acids of the broiler chickens at 35 days were measured and showed that the concentration of butyrate was greater in xylanase supplemented groups (Table 4) compared to PC and NC (P < 0.05). The dose response was only a trend but all treated groups were statistically higher than PC and NC. Acetate was unaffected by xylanase supplementation but propionate levels in PC were recovered in the xylanase groups (P < 0.05).

Table 4 - Treatment effects on caecal volatile fatty acids content (mmol/g digesta)

The morphologies of duodenum, jejunum, and ileum were measured through villus height and crypt depth. There was no significant effect on the crypt depth of the broiler chickens at 35 days of age. However, the villus height in the duodenum and in the ileum changed upon xylanase treatment; ileal villus height, and the VH:CD ratio in the duodenum and jejunum were significantly (P < 0.05) affected by the xylanase supplementation compared with the NC group. The dose response with T1, T2 and T3 was only numerical.

Change in bacterial population, increase in amounts of VFA’s and increase of VH:CD ratio constitute an array of data suggesting that the supplementation of Xylanase had a beneficial effect on the gut health of the animal. This has been previously demonstrated in other study (Liu and Kim, 2017).

The study presented here demonstrates that supplementation of xylanase at 10g/T enabled recovery of the growth performance obtained with the PC in a corn soy diet. Further supplementation of xylanase tended to result in additional improvements.

The data collected demonstrate that dietary supplementation of xylanase even at the lowest dose of 10 g/T of feed can result in significant improvements of broiler performance, nutrient utilization, beneficial microbial growth, and VFAs concentration.