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The role of yeast culture Saccharomyces cerevisiae as feed additive in Poultry

A.K. Panda, M.R. Reddy, S.V.R. Rao and N.K.Praharaj
Project Directorate on Poultry, Hyderabad .

In the current commercial poultry prac­tices, to achieve high levels of economic ef­ficiency poultry are raised under intensive production systems in densely populated colonies or flocks. The chickens are stressed by various factors such as over­crowding, vaccination, chilling, and/or over­heating. Under such circumstances feed additives like yeast culture have great sig­nificance for enhancing feed quality, produc­tivity and health.

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Yeast feeding as a supplementary feed has a long history. In 1925 Eckels and Williams published a report on the use of yeast as a supplementary feed for lactating cows. Brewer's yeast has been success­fully used as a protein source in ruminant diets. The application of low level of yeast (<1 % of dietary DM) first received attention in the 1950s. The use of yeast culture for ruminants and non-ruminants such as horse and pig are well documented. In

poultry the work is limited and the mode of action may be different from that in rumi­nants. Recently there has been consider­able interest in the use of some novel mi­cro-organisms to improve health and pro­ductivity of livestock and poultry and the use of yeast culture in their diets is receiv­ing renewed attention.

Yeast culture consists of natural live yeast cells grown and fermented in the media like molasses and grain mashes in the form of spores at low temperature. It includes both media and yeast conditioned for immediate enzymatic action upon en­tering the digestive tract. It is neither an antibiotic nor chemotherapeutic agent and is distinctly different from baker's yeast. Yeast culture is added as a digestive aid to. increase the nutrient availability and they will act by producing certain digestive enzymes.

Nutritive value of yeast

An excellent source of amino acids for poultry.

Good sources of mineral and vitamin B complex.

Live yeast boosts immunity levels in the system resulting in better protection against infection.

Live yeast has a constant interaction with crude fiber resulting in increased fiber digestion.

Yeast will produce unidentified growth factors which result in better production.

Live yeast culture augments the diges­tive processes by initiating the processes of fermentation.A source of digestive enzymes of vari­ous kinds.

Yeast used as feed additives

  • Torulopsis
  • Torulayeast
  • Torula Bovinae
  • Saccharomyces cerevisiae

Yeast culture in Poultry Production

Among several species of yeast (mentioned above), Saccharomyces cerevisiae is the ideal yeast for yeast culture production based on its growth and metabolic characteristics. The survivability of live yeast in the intestine of chicken is welt established. Taklimietal, (1994) conducted an experiment to study the viability of live yeast (Saccharomyces cerevisiae 1026) in broilers fed diet containing 0.1 % live yeast (5*10g). He found that the concentration of viable yeast cells was highest in crop followed by gizzard, small intestine and caeca in that order. Sefton, (1989) reported that addition of yeast culture Saccharomyces cerevisiae in drinking water resulted in the reduction of number of days required to reach the market weight, improving the liv-ability and feed conversion in broilers. Di­etary inclusion of Saccharomyces cerevisiae (Yeasacc) @ 1 kg per ton of feed in layer resulted in improved egg produc­tion, feed conversion and egg shell quality (Lim, 1992).Krugeretal., (1990) supple­mented the starter and grower commercial diets with 454 and 908g/ton of live yeast Saccharomyces cerevisiae and found a significant 3-point improvement in feed conversion, but no changes were noted in gain, livability, feathering, bone ash or carcass yield. On the other hand Me Dan­iel (1991) supplemented the broiler breeder diet with 0.5kg/ton of live yeast culture (Yea­sacc) at 20 weeks of age, and increased it to 1 kg/ton at 47 weeks of age resulting in no consistent effect on female reproduc­tive characteristics, rate of lay, egg specific gravity and egg weight.

At present time it is inevitable that the application of yeast culture shows little or no increase in production. The response of yeast feeding in poultry is inconsistent and seems to be influenced by several factors like the microbial strain used, the physic-chemical characteristics of diets, the mode of administration, dose rate as well as the physiological state of the birds. Further, there are a few published reports of pre­cisely controlled field experiments and the comprehensive assessment of their value has not been attempted in the form of a large scale coordinated field trial. The ex­istence of so many variable factors which is difficult to control under experimental conditions, indicate the need for further research.