Supplementation is widespread in poultry and swine, in particular, with reported benefits including an increase in feed conversion efficiency, the release of nutrients trapped in insoluble matrices and the release of oligosaccharides, with their positive effect on gut flora.
The review, carried out by scientists at the University of California, Davis, found there was a widespread reluctance to extend this supplementation to ruminants. This was based on the perception that ruminal hydrolysis made such enzymes ineffective and, in any case, could not be improved by supplementation.
Speaking to FeedNavigator, professor in the Department of Animal Science and co-author of the paper Ermias Kebreab said: “The literature is filled with conflicting outcomes when using exogenous enzymes. However, the studies also use all sorts of doses and substrates, so different results are to be expected. Research needs to narrow down on dose, diet, environment, stage of lactation – in dairy – and other variables, in order to understand the effectiveness better.”
The reported effectiveness might have deterred some researchers in the past, he said, but there was a need to find out why the enzymes worked in some conditions and not in others.
The Californian study mapped research relating to amylolytic, proteolytic and fibrolytic enzymes. Among fibrolytic enzymes, it focused on β-mannanase, targeting β-mannan in feed components including palm kernel meal, soybean hulls and soybean meal.
Feed conversion efficiency
Regarding β-mannanase, Kebreab said: “Most of the effectiveness shown related to improved feed conversion efficiency and lower cell counts (or lower bacterial load in milk) – which is a proxy for gut health. It has been shown to have a positive impact on fertility rates, as well.”
He explained why mannans can be detrimental to the animal’s immune system. “They can be recognized through the mannose receptor as foreign bodies, inducing an innate immune response in the gastrointestinal tract. A redistribution of the nutrients towards supporting the immune response decreases the optimal use of nutrients, depressing performance of the animal.”
One aim of the study, Kebreab added, was to encourage more research into the merits of some classes of exogenous enzymes. In particular, the paper called for more of a focus on mechanisms of action and the long-term effects of β-mannanase in ruminants, especially lactating dairy cows.
Further areas for future research, the paper concluded, should include the survival of exogenous enzymes in the rumen and cost-effective dosing.
‘Role of exogenous enzyme supplementation to improve nutrition and health of ruminants’, by Breanna M. Roque, Jayasooriya Appuhamy and Ermias Kebreab, Broadening Horizons (Feedipedia), No. 41, May 2017.