The challenge posed by β-mannans in UK poultry rations has been laid bare in a new report authored by a leading monogastric scientist Professor Jos Houdijk. 

UK poultry producers could improve the efficiency of their flocks, while reducing their environmental footprint, by taking steps to counter the negative impact of β-mannans in rations.

See also: New report outlines ways to manage nitrogen in agriculture

This is the message from a new technical summary – β-mannans in pig and poultry diets – how much of an issue are they in the UK? – written by Professor Jos Houdijk, head of the Monogastric Science Research Centre at Scotland’s Rural College (SRUC).

The report, commissioned by Elanco Animal Health, explains why β-mannans have a detrimental impact on bird performance and how supplementation with β-mannanase is one way of addressing the issue.

What are β-mannans?

Livestock, including poultry, derive most of their energy from carbohydrates, however, not all carbohydrates contribute equally to energy provision.

“The energy provision of carbohydrates is largely determined by their digestibility and/or fermentability,” explains Prof Houdijk.

“Those that are digestible can be broken down by absorbable sugar units, through the action of host enzymes secreted into the gastrointestinal tract – a process known as endogenous secretion.

“However, a significant proportion of carbohydrates consist of sugar units bound through β-linkages which can’t be broken down naturally as endogenous secretion doesn’t contain enzymes that are capable of breaking these bonds.”

He says β-mannans are one form of non-digestible carbohydrates, which are present in high levels in protein-rich feedstuffs in UK pig and poultry diets – such as soya bean meal.

Why are β-mannans a problem in UK rations?

High levels of β-mannans in poultry rations pose a challenge because they can have net negative effects on bird productivity.

Prof Houdijk says these negative effects include the ability to evoke unnecessary immune responses – described as a Feed Induced Immune Response (FIIR).

Explaining how this occurs, he says: “β-mannans often get stuck to the epithelial gut wall, because they’re too large to be absorbed, causing the immune system to recognise them as a pathogen challenge.

“This initiates a cascade of events, including immunopathological issues, which result in energy being diverted away from production for an immune response that isn’t needed.

“This FIIR causes resources to be diverted away from production.

“Therefore leading to reduced feed efficiency, also observed as an increased feed conversion ratio (FCR) in broilers, effectively telling us that feed is unnecessarily wasted.”

β-mannanase supplementation

Dietary supplementation with the enzyme β-mannanase, such as Elanco’s Hemicell, is one way of countering the negative impacts of β-mannans in poultry rations.

“Since poultry rations can contain significant levels of β-mannans, their breakdown through dietary supplementation of β-mannanase can improve feed efficiency and energy digestibility,” explains Prof Houdijk.

He says the report draws on recent reviews and studies into β-mannanase supplementation in both poultry and pig rations.

“This includes field studies in Europe and the Middle East, which found that supplementation of the enzyme led to a significant improvement in gut health, presented as a 1.04 improvement in Intestinal Integrity index.

“The Intestinal Integrity index, developed by Elanco, is also known as the I2 score and consists of grading 23 intestinal health conditions known to affect intestinal health and thus expected to impact performance, welfare and profitability (i.e. sustainability).”

The report concluded that supplementation with β-mannanase, as a means of breaking down β-mannans, delivers both production and environmental benefits through improved feed efficiency.

“The consequences of improved feed efficiency are that less feed is required for the same level of output. 

“Therefore, improving feed efficiency with β-mannanase supplementation, such as with Hemicell™ XT, can help to lower environmental impact from reduced resource input,” adds Prof Houdijk.

He says the report effectively highlights the challenge posed by β-mannans in UK rations, and how including β-mannanase in rations has the potential to both improve bird gut health and reduce the environmental footprint of poultry production.

The report can be downloaded here: https://bit.ly/3te0Gcw

 

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