Poultry Science Association Meeting: Cracks in mannan hypothesis under SBM
July 13, 2016
The global poultry industry is increasingly utilizing β-mannanase enzyme supplementation as a valuable option to enhance production. But are the purported benefits supported by the latest science?
New research results, unveiled at the 2016 Poultry Science Association (PSA) annual meeting, July 11-13 in New Orleans, call into question the value of single activity β-mannanase source formulations, particularly when used with soybean meal (SBM) based diets.
β-mannans (beta-galactomannans) are a form of fibre found in leguminous feeds including soybean meal. In general, they have been viewed as an undesirable component of poultry feed, for two main reasons. First, they are considered to have low capturable nutritive value. Second, they have been purported to trigger an immune response in the birds that needlessly consumes valuable energy. (A prevailing theory touted in some commercial messages to the poultry industry has been that β-mannans have a molecular pattern similar to some pathogens, which triggers a Feed Induced Immunity Response (FIIR) in poultry – thereby consuming energy that would be preferably directed to growth and performance).
Supplementation of poultry diets with β-mannanase (an enzyme that breaks down β-mannans) has been presented as a solution to this challenge, with single activity β-mannanase source formulations gaining significant commercial attention and use. However, emerging science indicates the story of β-mannans and β-mannanase is more complex, and in some ways fundamentally different, than originally thought. The new science presented at PSA is a major tipping point, offering new evidence and insights on the value of β-mannanase supplementation.
The information presented at PSA centres around a newly completed study led by Dr. Anna Rogiewicz of the University of Manitoba, located in Winnipeg, Canada – an institution recognized among the global leaders in novel feed ingredient and feed enzyme research.
The study examined, “β-mannans of soybean meal: Their enzymatic hydrolysis and the effect of β-mannanase on growth performance and immune status of broiler chickens.” This included an evaluation of four β-mannanase enzyme preparations, including one multi-carbohydrase enzyme formulation (with β-mannanase among several types of enzyme sources in the multiple activity formulation) and three different single activity β-mannanase source formulations.
The study involved three main components, starting with an analysis of the β-mannans content of the SBM. In vitro experiments were then conducted to evaluate the specific affinity of each of the β-mannanase sources towards the purified SBM β-mannan substrate.
Next, an in vivo broiler chickens study was conducted to evaluate the impact of dietary supplementation with corn/SBM based rations, among each of the β-mannanase source preparations. Broiler chickens were assigned to one of six dietary treatments (four with β-mannanase source formulations along with one positive control and one negative control), each consisting of 10 pens of five birds each. Birds were fed energy-deficient corn/SBM based diets containing 2900 and 3000 kcal/kg in the starter (0-10 days of age) and grower (11-21 days of age) phases.
In addition to evaluating impacts on growth performance, a major focus of the in vivo study was to evaluate the concept that SBM β-mannanse may be involved in triggering an innate feed induced immune response that would be minimized by β-mannanase supplementation.
Very low β-mannans content in SBM. The β-mannan content of SBM was shown to be very low, at only 1.08 % of the SBM. The water-soluble fraction of the β-mannans content was only 0.10% of the SBM (9% of the total β-mannan content).
The researchers observed that, as opposed to the high amounts of β-mannans present in guar or copra meals, this small amount in SBM is not likely to contribute to any increased intestinal viscosity in poultry fed corn/SBM-based diets.
Substantial breakdown with enzyme supplementation. In the subsequent in vitro experiments, SBM and its water-soluble fraction were incubated with each of the β-mannanase preparations under investigation. A moderate degree of β-mannan depolymerization was observed, as evidenced by mannose disappearance, ranging from 4.3 to 20.3% with SBM, and from 13.8 to 31.7% with the water soluble fraction.
No benefits shown in performance or immune response. However, results in the broiler chicken study showed no energy-saving related benefits attributed to use of the single activity β-mannanase sources.
Immune response trigger concept put into question. Further to the immune response results, the study did not find data to confirm the theory that β-mannans trigger an FIIR in poultry. Rather, the results of this study would indicate “no β-mannans FIIR response trigger” under corn/SBM based diets.
In the presentation at PSA, Dr. Rogiewicz placed these results in the context of broader studies and the growing body of knowledge around nutritional pathways to unlocking higher feed value and performance benefits for global poultry production. The University of Manitoba, with its long-standing research program looking at the effects of novel feed ingredients and enzyme technologies, led by Dr. Bogdan Slominski, is a leading authority that has partnered in recent years with another leading institution in this area, the University of Warmia and Mazury in Olysztyn Poland.
On the question of β-mannans and the potential benefits of β-mannanase, evidence and analysis from researchers at these institutions indicates substantial variations and important distinctions based on the various types of β-mannans and β-mannanase involved.
Single source benefits limited, questionable for SBM-based diets. The new broiler chickens study steers the body of evidence toward the conclusion that while single activity β-mannanase formulations may have significant value for certain non-traditional diets with lower quality ingredients – such copra or palm kernel meal based diets which are more prevalent in the Asia Pacific – the benefits are not validated when applied with SBM based diets used in the vast majority of global production.
Greatest potential lies with multi-carbohydrase enzyme approach. Broader research suggests that in fact the best pathway to address β-mannans, along with a full range of target substrates in poultry feed, is through a Multi-Carbohydrase enzyme approach. The right Multi-Carbohydrase enzyme formulation, which may contain an effective type of β-mannanase as not the only enzyme but rather one of several complementary and synergistic enzyme activities, can produce substantial benefits for SBM based poultry production. The level of β-mannanase in a Multi-Carbohydrase formulation can be optimized to match the type and level of β-mannans targeted, in a strategically calibrated approach that utilizes the benefits of “working together” with other enzyme sources and activities in the formulation.
