Feed Induced Immune Response (FIIR) as a response to β-galactomannans is a potential threat to broiler performance and uniformity. β-galactomannans can be considered as the leading molecules and are most prevalent in a wide variety of feed immunogenic ingredients in poultry, including soybean meal (SBM), sunflower meal, palm kernel meal, copra meal, and sesame meal.
Since soybean meal is a major protein source in feeds produced around the world, β-galactomannans are present in most feeds. β-galactomannans in SBM are linear polysaccharides composed of repeating β – (1-4) mannose β -(1-6) galactose and/or glucose units attached to the β -mannan backbone. They are highly viscous, water soluble, heat-resistant compounds that survive the drying/toasting phase of soybean processing.
β-galactomannans can be recognized by the innate system and considered by the intestinal mucosa as Pathogen Associated Molecular Patterns (PAMP) by several Pattern Recognition Receptors (PRR), including the serum protein mannose binding lectin MBL, as well as several cell surface receptors on key immune system cells including mannose receptor (MR) and others (DC‐SIGN) on key immune system cells. Consequently, they provoke an intestinal micell-immune response which is energy consuming and wasteful. The association of mannan with the surface of numerous pathogens has likely led to β -galactomannan’s conserved recognition by the innate immune system.
The innate immune system can also be activated when molecular patterns also found in high molecular weight mannan present in leguminous feedstuffs, such as soybeans. They are detected by the mannose binding lectin thus associating into structures that have multiple CRD (carbohydrate binding domains). This can potentially induce a strong and costly feed induced immune response.
Recently β-mannanase has been used to hydrolyze β-galactomannans into mannan oligosaccharides fragments that can no longer be recognized by toll like receptors (MBL). Thus, by negating FIIR, beta mannanase can potentially help conserve valuable energy and that can be used towards improved growth and performance.
Materials and methods
A broiler experiment was conducted to evaluate the effects of β-mannanase on live performance and uniformity at market age (Table 1). For this trial, birds were grown using three feeding phases for each treatment to 43 days using 5 treatments and 8 replications with 50 birds placed per pen. Treatments consisted of:
1- Positive control diets ranging from 3217 to 3086 Kcal/kg and 21.75 to 18.00 % Crude Protein; 2 – As 1 minus 42 Kcal/kg in each phase; 3 – As 1 minus 77 Kcal/kg in each phase; 4 – As 2 + 225 g of β-mannanase/metric ton of feed in each phase; 5 – As 3 + 400 g of β-mannanase/metric ton of feed in each phase.
Results and discussion
Results from the present study showed that adding β-mannanase at 225 g/metric ton of feed significantly improved weight gain and live weight uniformity in energy reduced diets (Table 1). The live performance benefit of the energy-reduced feed was restored to that of the positive control which contained an additional 42 Kcal/kg of ME. β-mannanase when added at 400 g/metric ton of feed significantly improved final weight, FCR, and uniformity when compared to treatment 3.
Weight adjusted feed conversion (WAFC) benefit was superior to that of the positive control which contained an additional 77 Kcal/kg ME. β-mannanase significantly improved live weight uniformity compared to the energy-reduced ration by lowering the coefficient of variation by approximately 2 percentage points.
Further studies are required to confirm these findings since improvements in live weight uniformity in grow-out barns will translate to an improvement in the consistency of processed poultry products.
References are available on request
Presented at the Australian Poultry Science Symposium, New South Wales, Australia