Live yeast in ruminant nutrition

Being considered as the oldest and best understood microorganism, the yeast Saccharomyces cerevisiae still remains valuable to mankind's future. Since ages, Egyptians followed by Romans, used yeast to leaven bread and to produce alcoholic beverages. This clever bug has definitely a marvellous habit of evolving to suit its environment and has been the business vault of many industries. Its "probiotic success" in animal nutrition has been as a consequence of the European ban of dietary antibiotic growth factors due to resistance to human pathogenic bacteria. Taking this opportunity, the Lesaffre Group, world-leading yeast manufacturer, has introduced a thermostable live yeast (Saccharomyces cerevisiae NCYC Sc 47) on the feed additive market. This probiotic yeast is commercialised by its Animal Nutrition & Health business unit "Lesaffre Feed Additives - LFA", having the "savoir faire" of the Group. This live yeast is authorised 11 species including ruminants and more recently rearing calves. 

Over the last 30 years, our knowledge of the role of yeast in animal diets was presented in the form of scientifically proven arguments. Considerable research works have been published to review the major milestones that have helped define the action of live yeast in ruminants. According to Jouany in 2000, the number of published papers on probiotics yeast for ruminant went on increasing rapidly from 1950 to 2000 so that around 80 papers were published per year in peer-reviewed journals. From 1950 to 1980, much work has been devoted to show improvement in animal performance and animal health with yeast. Further research efforts gave a better insight on the understanding of basic mechanisms and modes of action in the 90's. Nowadays, in the advent of new fashionable biotechnological techniques, a more precise view on microbial activities and functionalities can be acquired. However, one must keep in mind that the ultimate goal is to define the application and production strategies that can optimise the animal's response to probiotic yeast supplements. And in this context, much effort is still needed to link research advances to what is in fact happening in field conditions. 

The most obvious example is the ruminal acidosis, a frequent digestive disorder in ruminants that causes health problems leading to substantial deterioration in productivity. According to an extensive literature review, the definition of acidosis is still unclear. Scientists around the world give their own description and definition of the acidosis which basically originates from an accumulation of strong acids in the rumen due to the consumption of a large proportion of readily fermentable carbohydrates by the animal. As it is chemically admitted, acidity of any given medium is generally evaluated by the measurement of pH. Based on this fact, different thresholds (by different researchers, from different countries) have been established to first diagnose ruminal acidosis and then classify into whether it is sub-acute, sub-clinic, sub-chronic, latent or acute, clinic or chronic acidosis. Mean threshold pH values and pH drop against time have been, for a long time, the sole indicators of ruminal acidosis. As a result, these definitions are more experime tally-based than what can be perceived from the field. 

Frequently measured in different living medium like soil, wine, milk, rivers and oceans, the redox potential (Eh) describes the activity of the microbial inhabitants. In the rumen however, Eh measurement has been performed less due to its high anaerobic requirement. In the late 50's, a Scandinavian veterinarian evaluated rumen digestion and health in high-grain fed and bloated animals and demonstrated that animals had different ruminal Eh ranges. It renewed interest in the late 80's where Marounek and his colleagues measured the Eh in different parts of the di- gestive track of herbivores. For 7 years now, LFA Ruminant research team devoted much interest in the proper measurement and interpretation of such parameters that can be applied to the rumen environment. After the setting up of a redox measure- ment methodology, the gathered Eh data proved to be complementary to pH in order to better approach rumen bioenergetics and the involved mechanisms. Furthermore, the redox and bioenergetic concept coupled with evolving bio-molecular techniques, such as DDGE, RFLP and the latest pyro-sequencing technique, allowed a better understanding in the mode of action of live yeast in ruminants. For instance, a comparison between two different buffering agents: live yeast, as a biological modulator and bicarbonate, as the traditional chemical buffer, showed different actions on rumen physico-chemical, fermentation and fibre degradation parameters. 

Based on several recent publications in well-known journals and the quick interest of researchers around the world, the "Bioenergetic & Biomolecular" Concept captivates! With collaborations with the most eminent researchers in Thermodyna- mics, Microbiology, Modeling and Nutritionists, LFA's motivation is not only to acquire more knowledge in yeast-based or side-products, but also to be involved in a holistic approach to ruminant physiology and nutrition to ultimately provide ready-made solutions to the feed industries and feed users. New measuring redox probes for non-cannulated and pasture-fed animals along with modelling of Eh regarding diet composition, feed additives, etc. are our objectives ... to better advise our clients is our priority.