Effect of different levels of guar gum and and β-mannanase on the performance and immune response of broilers

Guar gum is a galactomannan compound and is anti-nutrient in high amounts and can have prebiotic properties in low amounts in the diet, β-mannanase enzyme reduces its anti-nutrient state by reducing the molecular weight of this compound. Protein is the most expensive component of the diet, which is mostly provided provided by soybean meal in commercial diets. Due to the high cost and limited soybean cultivation area, numerous studies have been carried out on the use of other vegetable meals such as guar meal in chicken nutrition. Cyamopsis tetragonoloba is a drought-tolerant legume that is used primarily in the chewing gum industry because its seeds contain large amounts of guar gum. Guar gum is extracted from the seeds of the guar plant; it is a natural nonionic branched polymer in which the -D-mannopyranosyl unit is attached to 1-4 and the unit a-half pyranosyl unit is used as the side chain takes place. Guar has been used in many applications such as thickeners, ion exchange resins, suspending agents, pharmaceuticals and paper (Wang and Wang, 2009). In order to produce gums, the guar seeds are split, producing a high protein germ fraction and a low protein shell fraction as by-products. These two fractions are typically recombined to produce guar meal with a crude protein level of 35-47.5%, depending on the relative concentrations of the two fractions (Chenault et al., 2002). In addition, approximately 88% of the nitrogen content is true protein, making it possible to use as a component of poultry feed (Lee et al, 2003a). The purpose of this study was to evaluate the different levels of guar gum and with and without addition of β-mannanase enzyme on the performance and immune response of broilers.

For this reason, 312 Ross-308 broiler chickens from 1 to 42 days of age were used based on a completely randomized design with 6 treatments and 4 replicates (13 broiler chicks in each replicate). The six experimental treatments were as follows: corn–soybean meal basal diet:1) control diet, 2) control diet + supplements Fermacto (0.18%), 3) control diet + low gum (0.35%), 4) control diet + high gum (0.70%), 5) control diet + low gum (0.35 percent) + β-mannanase enzyme, 6) control diet + high gum (0.70 percent) + β-mannanase enzyme. Feed intake (FI), body weight gain (BWG) and feed conversion ratio (FCR) were recorded at the end of the period. Two chicks per dietary replicate were injected (32 d.) with either 0.5 mL of 2.5 % SRBC intramuscularly into each breast muscle. Heparinized blood was collected from the wing vein at (39 d.) by venipuncture 6 and 12 d after immunization with SRBC. Samples were frozen at -20°C until analysis. The hemagglutination assays were performed as described by Cheema et al (2003) for RBC. In order to enumerate the Lactobacilli and Escherichia coli on day 42 of breeding period, one chick was selected from each replicate according to protocol described by Corduk et al (2008). The data were analyzed in a completely randomized design by ANOVA using the General Linear Model (GLM) procedure of SAS Institute.

The results showed that the highest feed conversion ratio was seen in high gum 0.70% diet (no- enzyme) and the lowest one was in low gum diet (with enzyme). In agreement with the results of this experiment, Justina et al (2018) showed that chicks fed with high soybean meal and high soybean meal + guar gum diets with added β-mannanase significantly improved blood glucose and anabolic hormone homeostasis, FCR, digestible energy, and digestible amino acids compared to chicks fed with same diets without β-mannanase. The results of this experiment showed that there was no significant difference in IgG and IgM antibody titers between treatments. Unlike our results, the addition of β-mannanase to the enhanced β-galactomannan diet eliminated most of this immune-related signal, indicating that the feed-induced immune response within jejuna was eliminated by the addition of β -mannanase. They also observed changes in specific metabolic and intestinal functional pathways of birds fed β-mannanase. These observed changes in β-mannanase-fed birds may be an enhanced performance and feed conversion mechanism observed in birds given β-mannanase in their diet (Arsenault et al 2017). The reports show that the enzymes be able to accidentally attack the cell wall polymers and thus move to the center of the polymer. Breaking down any polymer chain will significantly reduce the molecular weight of the polymer solution, thereby reducing its anti-nutritional effects (Chacher et al 2017). The dietary β-mannanase had potential to improve daily gain and feed efficiency and apparent ileal digestibility while decreasing digesta viscosity of broiler (Balasubramanian et al 2018). Mannan oligosaccharides bind to type 1 fimbriae to reduce pathogenic bacteria, increase goblet cells, thus, lead to the production of antibacterial mucus and create the conditions for the growth of beneficial bacteria, and eliminates competition. The balance between pathogenic and beneficial bacteria increases the length of the villi and decreases the depth of the crypt, which indicates an improvement in the morphology of the intestine. Improving the morphology of the intestine increases the activity of digestive enzymes and thus increases digestion. In addition, mannan oligosaccharides activate macrophages in intestinal lymphatic tissues, thereby improving cellular and humoral immunity. Mannan oligosaccharides also increase butyric acid production and decrease intestinal pH in broilers. These combined mechanisms promote the growth rate and performance of broilers (Chacher et al 2017).

According to the results, Addition of guar gum and betanamase to the diet had no effect on the performance and immune responses of broilers compared to controls. However, the addition of guar gum with the β-Mannanase enzyme increased the microbial population of jejunum and ileum lactobacilli, therefore, this is also recommended.