Using diet modelling


to predict the dynamic effect of live yeast supplementation in ruminants


By Mark McFarland, Lallemand Animal Nutrition UK & Ireland


Summary High output farming practices require a higher plane of nutrition, which typically includes increased levels of fermentable carbohydrates. This can put the animal at risk of developing metabolic disorders, in particular, challenges to rumen stability and sub-acute rumen acidosis (SARA). Traditionally, specific live yeasts have been used to overcome rumen challenges by increasing rumen pH to optimal levels in situations such as feed transition (weaning, grazing, step-up feeding programs) or during periods of stress (high temperatures and transportation). Recent research has demonstrated that specific live yeast can have


a beneficial impact on fibrolytic microbial populations and digestibility of the fibre proportion of the diet. The live yeast is a valuable tool which allows maximisation of the diet, giving the farmer and nutritionist the possibility to either increase milk or meat revenue per kg of feed, or to optimise feed cost with similar revenue. Such technology can be particularly useful in maximising energy from the feed. Modelling the quantitative response of live yeast on rumen pH and fibre degradation in a feed formulation programme, can allow nutritionists and farmers to formulate for improved feed efficiency and income over feed cost (IOFC).


Introduction How can specific live yeast favourably modify rumen function? Could it be considered as a tool to optimise ruminant diet formulation? In monogastric diet formulation programmes several feed additives,


for example enzymes, have been accepted for decades for improving the productive value of commercial feeds and allowing greater flexibility in feed formulation (least cost formulation). These technologies are supported by a positive documented response on the digestibility of feeds. For ruminants, Dr C. Sniffen, from Cornell Institute, defines rumen


modifiers as feed additives which alter ruminal fermentation and microbial growth, while having a positive impact on feed efficiency (Sniffen et al., 2010). Potential additives include ionophores, live yeasts, fermentation products, essential oils and enzymes. To be used in diet formulation models, rumen modifiers should be proven to have the capacity to modify some key steps of the biological process of rumen digestion. Furthermore, those mechanistic effects need to be validated by practical responses on feed efficiency and commercial production.


PAGE 32 JULY/AUGUST 2021 FEED COMPOUNDER


Key role of the rumen in digestion • A huge fermenter (up to 200L) with unique digestive capacity


• Over 100 billion microbes/mL of rumen fluid


• A complex ecosystem with anaerobic bacteria, ciliate protozoa, fungi and archaea


• Up to 75% of the animal’s feed is digested in the rumen Case study:


selected live yeast as a rumen modifier Rumen function optimisation is a key target for producers to improve overall animal production efficiency. Indeed, the rumen hosts a complex anaerobic microbiota responsible for degradation and fermentation of the main part of dietary components ingested by the animal. However, many factors can impair rumen function. In this context, microbial feed additives such as live yeasts, are an important tool to improve feed efficiency and overall performance. Effects and modes of action of the live yeast strain Saccharomyces


cerevisiae CNCM I-1077 (LEVUCELL SC, Lallemand Animal Nutrition) on rumen microbiota have been extensively studied. The main impacts attributable to this strain include; i) the stabilisation of ruminal pH, which is demonstrated to be a causal link to interactions with lactate-metabolising bacteria, ii) increase in fibre degradation and the subsequent improvement in digestibility due to interactions with plant- cell wall degrading microorganisms, and iii) improvement in rumen maturity which is demonstrated by S. cerevisiae CNCM I-1077’s action in favouring microbial establishment in young ruminants (Chaucheyras- Durand et al., 2008).


NDF degradation effect In sacco trials demonstrate the positive effect of S. cerevisiae CNCM I-1077 on neutral detergent fibre (NDF) fraction degradability of more than 200 different forage samples, including: grass silage, maize silage, straw, rye grass hay, alfalfa hay, annual rye grass (pasture), meadow hay etc. Saccharomyces cerevisiae CNCM I-1077 is found to increase NDF digestibility by 3 to 8 units, depending on the type of forage and its own degradability (Guedes et al., 2008; Guedes et al., 2015; Chaucheyras-Durand et al, 2010, Ding et al, 2014).


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