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Brewers yeast

Datasheet

Description
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Common names 

Brewers yeast, brewer's yeast, top-fermenting yeast, brewers' dried yeast, brewers' yeast dehydrated [English]; levure de brasserie, levure de brasserie déshydratée, levure de brasserie liquide [French]; levadura de cerveza [Spanish]; levedura de cerveja [Portuguese]; Biergist [Dutch]; Bierhefe [German]; lievito de birra [Italian]; فطريات الخميرة [Arabic]; drożdże piwowarskie [Polish]; 釀酒酵母 [Chinese]

Feed categories 
Related feed(s) 
Description 

Brewers yeast is a by-product from the breweries, which use the micro-organism and fungal yeast Saccharomyces cerevisiae. Brewers yeast is obtained by the removal of yeast after the brewing process and subsequent inactivation by means of organic acids (Crawshaw, 2004; Hertrampf et al., 2000). Brewers yeast is used as a flavouring ingredient in the food industry, and as feedstuff for pigs, ruminants, poultry and fish (Tacon et al., 2009; Crawshaw, 2004; Hertrampf et al., 2000). Brewers yeast is mainly a source of protein, vitamins and minerals (Stone, 2006). Yeast inactivation is necessary to prevent further fermentation after consumption by animals, that may cause severe gastro-intestinal problems in pigs (Neame, 1981 cited by Crawshaw, 2004). Inactivated brewers yeast is a highly valuable source of protein, phosphorous and B vitamins (Crawshaw, 2004). Brewers yeast may be fed fresh (liquid form) or dried (brewers dried yeast), which is costly and thus only used in specialty feeds (Chauvel et al., 1988).

Note: yeast by-products obtained from other micro-organisms like Candida spp., Pichia spp. or Phaffia (Tacon, 2015) and live yeasts used as probiotics are beyond the scope of this datasheet.

Distribution 

Brewers yeast has been known since Antiquity as remnants of bread making chambers have been found in Egypt, dating back 4000 years. Brewers yeast has been used for industrial beer production since the late 18th century, and for livestock feeding since the early 20th century in Germany. In this country, during World War I, brewers yeast represented up to 60% of the protein previously provided through imports of fodder (Braude, 1942). Brewers yeast is the second largest by-product from brewing (Huige, 2006). In 2011, world beer production was 184 million m3 (FAO, 2016). Using a yeast production ratio of 2.7 kg/m3 (0.7 lb/US barrel), it can be estimated that brewers yeast production was about 497,000 t in 2011 (FAO, 2016; Huige, 2006). Brewers yeast is available worldwide. Main beer producers are China, the USA, the EU, Brazil and Russia (FAO, 2016). Beer production mainly occurs during summer which makes yeast production higher during this period of the year. Drying brewers yeast is a way of enhancing yeast availability throughout the year (Boessinger et al., 2005).

Processes 

Storage

Brewers yeast has a limited shelf-life and may suffer tremendous losses of total solids during storage. To prevent these losses, it is necessary to chill yeast slurry to below 5°C. Chilling also prevents yeasts from losing their cell constituents (i.e. protein) as a result of cell autolysis at ambient temperatures (Huige, 2006).

Inactivation

Beer production yields 5 times more yeast than the amount required for beer processing (Crawshaw, 2004). At the end of the process the yeast is removed from the batch by centrifugation, and then washed free of beer. It is still alive and could have deleterious effects during storage or when fed to animals. It is thus necessary to inactivate (kill) it before using it. This can be done through heat treatment (80°C at the brewery) and/or by addition of organic acids on the farm (Chauvel et al., 1988). Brewers yeast contains valuable components such as ribonucleic acid (RNA) and vitamin D, which can be extracted before the yeast is sold fresh to farmers, feed companies or the food industry (Tacon, 2015; Hertrampf et al., 2000).

Removal of bitterness

If the yeast contains hop residues, it may have a bitter taste that makes the feed unpalatable if included in large amounts. The bitter taste can be removed by mixing the slurry with a solution of sodium hydroxide and sodium phosphate that raises the pH to 10, after which the mixture is concentrated, washed and dried (Priest et al., 2006).

Drying

Yeast is usually drum-dried, which requires expensive machinery and energy. The process is economical only in large breweries. The yeast can also be mixed with brewer’s grains and dried as a mixture in a steam-tube drier. This method increases the value of the spent grain. Brewers dried yeast has to be ground after drying (Hertrampf et al., 2000).

Nutritional aspects
Nutritional attributes 

Brewers yeast is mainly a source of protein as it contains about 50% DM of crude protein (40-56% DM). However, as noted in Potential constraints below, the nitrogen of brewers yeast may contain up to a third of RNA nitrogen, which does not correspond to actual protein and is not usable by non-ruminants. Depending on the process, brewers yeast can contain fibre, starch and lipids, in amounts ranging from negligible to small but significant. Brewers yeast is an excellent source of B-complex vitamins, nucleic acids, vitamins and minerals, including a biologically active form of chromium known as Glucose Tolerance Factor (Ferreira et al., 2010). Brewers yeast contains various immunostimulating compounds such as β-glucans and mannan oligosaccharides (White et al., 2002). Nucleic acids also have an immunostimulating effect (White et al., 2002).

Potential constraints 

Ribonucleic acids

A limiting factor to the utilization of brewers yeast as a protein source is its high nucleic acid content, primarily ribonucleic acid (RNA), which may account for 33% of the total nitrogen. This can result in high uric acid in the blood of monogastric mammals fed brewers yeast (Ferreira et al., 2010). Uric acid has subsequent toxicological effects such as disturbances in the metabolism of fat, carbohydrates and uracil (Heaf et al., 1976). Some RNA-extracted brewers yeasts are thus sold to prevent this problem (Ferreira et al., 2010).

Ruminants 

Brewers yeast can be used as a feedstuff in ruminant diets. Large quantities of yeast are discharged as slurry from breweries or from the alcoholic fermentation of sugarcane, and might be as useful as the vegetable meals (especially cotonseed meal) for ruminant diets (Hennessy et al., 1993). Some yeast slurries are dried, which inactivates the yeast; but the high energy costs of drying might reduce the price competitiveness of the product against other protein sources. The influence of yeast on ruminant performance, either in dried or liquid forms, is detailed below. In all these studies, it was generally concluded that yeast can be used as an alternative protein source in rations for ruminants because it does not change animal performance and it has equivalent or higher nutritional value than soybean meal.

Note on yeast as probiotic

As indicated in the introduction, the probiotic effects of live Saccharomyces cerevisiae are beyond the scope of this datasheet. Supplementation of live yeast probiotics on intake, production and rumen fermentation characteristics has been widely studied during the past decades. Quantitative reviews generally reported modest improvement in rumen fermentation patterns, feed digestibility, dry matter intake, milk yield, fat corrected milk yield and milk fat content (Desnoyers et al., 2009; Robinson et al., 2009; Poppy et al., 2012; Elghandour et al., 2015). However, the response to yeast supplementation is not constant, depending on dosages, feeding times and frequencies, and strains (Elghandour et al., 2015).

Digestibility and energy values

In a comparison of dairy cattle diets supplemented either with soybean meal or with liquid brewers yeast, the digestibility of DM, gross energy, protein and ADF of a dairy cattle diet were higher with yeast supplementation (Steckley et al., 1979). But this effect is not consistent (e.g. no effect was found by Freitas et al., 2015). In goat kids and lambs, digestibilities of DM, OM, total carbohydrates and NDF were improved with increasing levels of yeast in the diet as a substitute for soybean meal (de Lima et al., 2011; Rufino et al., 2013). Rations with dried yeast showed the highest values of total digestible nutrients. The effect appears to be quadratic, with maximal digestibility coefficients for diets with approximately 45% inactive dried yeast (Rufino et al., 2013).

Dairy cows

In dairy cattle, the inclusion of dried brewers yeast as a replacement for soybean meal at up to 20% of the total dietary DM did not affect intake, digestibility or performance (Nursoy et al., 2003; Freitas et al., 2015). Some positive effects were observed, such as a low rumen NH3-N level and a high acetic acid concentration (Nursoy et al., 2003). Thus, dried yeast seems to be a valuable protein source in dairy cow diets. Liquid forms, such as brewers yeast slurry, can be fed to dairy cattle as an alternative to soybean meal, up to 12% of the diet DM, without any detrimental effect on DM intake, milk production and milk organoleptic quality (Steckley et al., 1979). Milk yield for diets with 30% wet brewers grains was higher with added liquid brewers yeast than without it (+1 kg/cow/day, West et al., 1994).

Growing cattle

In heifer calves fed a maize silage-based diet, the addition of liquid brewers yeast, up to 9% of the total DM, led to higher DM intake (+1 kg) and daily weight gains (+ 500 g/d). These performances were similar to those obtained with soybean meal supplementation. DM intake was higher when yeast was fed free choice or mixed in the diet than sprinkled on top of the basal ration (Grieve, 1979). In steers fed native pasture hay, there was no improvement in live-weight gain, or in feed conversion efficiency, when up to 4.4 kg of yeast slurry (i.e. 423 g DM) was added to the basal diet. However, when replacing cottonseed meal and alfalfa chaff as a protein source in grain-based feedlot diets, increasing dietary levels of yeast (0 to 61% of total DM) were associated with increasing live-weight gains and carcass yield (Hennessy et al., 1993). There was a trend towards decreasing feed costs when replacing cottonseed meal and sorghum grain with yeast slurry. However, the large range in slurry DM contents (4.8-15.6%) and crude protein content (43-51% DM depending on the load, Grieve, 1979) requires close monitoring, with daily changes made to the amounts of slurry offered to maintain dietary N and protein levels. These ranges could make it difficult for commercial feed compounders to produce a diet of consistent quality (Hennessy et al., 1993).

Sheep

Nutrient intake, growth performance and meat quality of lambs fed diets containing increasing levels of inactive dried yeast (0, 33, 67 and 100% on a dry matter basis) to replace soybean meal were globally not affected. 100% inactivated dried yeast in lamb diets could even improve the carcass and meat quality by reducing the deposition of subcutaneous and intramuscular fat (Rufino et al., 2013).

Goats

In Brazil, several experiments were conducted with Saanen dairy goats (primiparous and multiparous, pre and postpartum) or goat kids (¾ Boer x ¼ Saanen or Saanen). Each time, inactivated dried yeast from sugarcane fermentation was used as an alternative protein source to soybean meal in maize silage based diets (soybean meal vs. soybean meal + yeast vs. yeast alone representing 23% of the total dietary DM). The nutritive value of the diets was unchanged and there was no effect on milk yield, live-weight gain or feed conversion efficiency (de Lima et al., 2011; de Lima et al., 2012; Gomes et al., 2012; Gomes et al., 2014; Molina et al., 2016). However, the milk production efficiency (kg of milk produced/kg of crude protein ingested) was better in goats fed the dried yeast diet (de Lima et al., 2012).

Pigs 

Brewers yeast is a valuable component of pig diets. An excellent source of protein for swine, brewers yeast contains most of the essential amino acids in adequate quantities. However, it is somewhat deficient in methionine and cystine (Huige, 2006). Liquid pig diets allow the use of fresh brewers yeast. Inactivated yeast is generally recommended for animal feeding since live yeast may grow in the intestinal tract and compete for nutrients (Blair, 2007). However, there are some positive results from feeding live yeast to pigs (see below). It is recommended that brewers yeast represents 2-5% of the diet, and it can replace up to 80% of the protein (Blair, 2007). 

Fresh brewers yeast

Fresh brewers yeast is an excellent source of high quality, highly digestible protein. It also contains enzymes and co-factors which benefit pig health and performance (Shurson, 2009). However, brewers yeast is seldom used fresh as it spoils quickly, and may cause watery flesh in pigs. When fed in large quantities to pigs, a mineral mixture rich in calcium and with a low phosphorus content must be used, and a supplement of vitamin B12 should be included. Pigs should be fed a litre of cooked or boiled yeast daily at the start of the fattening period, rising to 2 litres daily at the end (Blair, 2007). Fresh yeast should not be fed to suckling sows because of the danger of diarrhoea in piglets (Blair, 2007).

Including 2 kg of yeast at 15% of total solids in the daily diet of rapidly growing pigs could provide 42% of the lysine requirements and 51, 55, and 49%, respectively, of the threonine, isoleucine, and tryptophan requirements, whereas only 31% of requirements for both methionine and cystine were satisfied (Lonsdale, 1985). In Germany, pigs were fed an average of 1.9-3 L/d of yeast slurry, completely replacing protein concentrates. Yeast solids were valued 20% above soybean meal. In addition to providing numerous vitamins, yeast is also considered important in pig diets because it contributes selenium, copper, and phosphorus (Witting et al., 1978). In a later study, liquid brewers yeast was included in growing pig (24-135 kg) diets at 10% (DM basis). It yielded higher daily weight gain (800 vs. 743 g/day for males and 797 vs. 788 g/day for females) than a soybean meal based diet. Feed conversion efficiency was similar for both groups of pigs. Carcass quality was not affected by the inclusion of liquid brewers yeast. However, yield of ham was higher in pigs given the yeast-containing diet (Mazzocco et al., 1989). In a study in the UK, pigs were fed up to 3.4 L/d of yeast slurry (13% DM) with 1-1.5 kg of barley supplemented with a mix of mineral/trace elements. The results were excellent and this was attributed to a better utilization of barley when the yeast was present. Due to the alcohol in the yeast slurry, pigs showed symptoms of inebriation. The animals became docile, rather than disruptive, which may be advantageous for reducing stress in a controlled environment pig house (Neame, 1981 cited by Huige, 2006).

Dried brewers yeast

Brewers dried yeast was included at 15% in pig diets in order to replace 7% fishmeal and provide 12% of the digestible crude protein in the diet. Brewers yeast resulted in higher live-weight gain and an improved feed conversion ratio. However, it was recommended not to offer more than 12% dried brewers yeast to pigs as higher levels decreased diet intake (Evans, 1952).

Spent brewers yeast

Spent brewers yeast could be used as an effective protein supplement in pig diets. Feeding weaned piglets on diets containing 2.5 or 5% spent brewers yeast over a period of 95 days had no effect on growth or carcass quality (Sreeparvathy et al., 2012).

Poultry 

Worldwide, poultry is the most important user of brewers yeast as a feed (Mordor Intelligence, 2016). Brewers yeast is an excellent source of protein of high biological value and digestibility, thus a very valuable component of poultry diets. However, brewers yeast is mostly used in poultry for vitamins of the B complex and for unidentified but important growth factors in poultry production. Brewers yeast is usually included at levels of 2-5% in poultry diets, but if its price is low, it can replace up to 80% of the animal protein that additional calcium is added. Dried brewers yeast replaced fish meal at up to 9.3% in broiler diets with no differences in growth and feed efficiency (Ergül, 1988). In Nigeria, in broiler chickens fed a high-fibre diet, including 25% of palm kernel, the addition of dried yeast was cost effective when included at 0.15 to 0.3% of the diet. The weight gained by chicks fed 0.45 and 0.6% yeast was not sufficient to cover the cost of the yeast product, and feed intake was depressed at 0.6% inclusion (Onifade et al., 1996).

Rabbits 

Brewers yeast is a potential and suitable high quality source of protein for rabbit feeding with a high digestibility (Battaglini, 1979). Organic matter digestibility was estimated at 86% (Grandi et al., 1986). In commercial or control feeds, the inclusion rate is generally low, from 2 to 4% (Halga, 1974; Battaglini, 1979; Kermauner et al., 1996). In experimental studies, brewers yeast can partially or even completely replace soybean meal in rabbit diets, and inclusion rates can be as high as 20% of the diet without alteration of growth, slaughter performance or health status (Seevaratnam et al., 1989; Abreu et al., 1994; Scapinello et al., 1996). This equivalence between the proteins of brewers yeast and soybean meal is mainly explained by their high digestibility and their quite similar amino acids profiles: a high level of lysine associated with a clear deficiency in sulphur-containing amino acids (Lebas, 2013). Brewers yeast is usually used in the dried form. A smooth dehydration such as spray drying is preferable to a more brutal process such as drying with a rotation roller, which may cause a higher mortality of animals through acute enteritis (Scapinello et al., 1999).

Fish 

Brewers yeast has potential in fish diets as a replacer of fish meal (Oliva-Teles et al., 2001; Rumsey et al., 1991a; Rumsey et al., 1991b; Rumsey et al., 1990). It has subsequently been introduced in commercial diets for several fish species, including salmonids (Ferreira et al., 2010). As the cell walls in brewers yeast may be of low digestibility in fish, they can be removed or disrupted to improve brewers yeast feed value in fish (Rumsey et al., 1991b).

Salmonids

Unlike mammals, salmonids are able to handle the high dietary levels of nucleic acids that are found in brewers yeast, by virtue of their very active liver uricase (Rumsey et al., 1991a; Kinsella et al., 1985). Brewers yeast could replace 50% of fish meal protein with no negative effects in fish performance. Moreover, the inclusion of up to 30% brewers yeast in the diet improved feed efficiency. However, feeding brewers yeast is found to cause reduced N digestibility (as with other single cell proteins). This could be due to cell walls that could be profitably disrupted to improve the digestibility of brewers yeast in lake trout (Salvelinus namaycush) (Rumsey et al., 1990). In rainbow trout (Oncorhynchus mykiss), when brewers yeast was included at up to 25% of the diet, fish growth was faster and feed conversion more efficient than with the control. Higher levels of brewers yeast were less palatable but fish did not appear to be adversely affected physiologically by high dietary levels of RNA nitrogen (Rumsey et al., 1991a).

Other fish species

In seabass (Dicentrarchus labrax) juveniles, brewers yeast replaced up to 50% of fish meal in isonitrogenous, isoenergetic diets. At up to 30% brewers yeast did not affect feed intake or fish growth. Feed conversion ratio was improved as well as N retention. The addition of methionine was ineffective (Oliva-Teles et al., 2001).

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 93.6 1.8 89.1 97.0 107  
Crude protein % DM 48.9 3.8 39.3 56.8 108  
Crude fibre % DM 1.8 1.3 0.1 4.4 56  
NDF % DM 8.8 9.4 0.0 20.7 6  
ADF % DM 2.5 2.5 0.0 5.7 6  
Lignin % DM 0.8 0.8 0.0 1.7 6  
Ether extract % DM 2.4 2.4 0.0 8.2 34  
Ether extract, HCl hydrolysis % DM 4.1 1.2 2.2 6.0 34  
Ash % DM 7.0 1.1 5.1 9.3 86  
Starch (polarimetry) % DM 10.9 7.0 0.0 17.5 5  
Total sugars % DM 1.9 1.3 0.3 2.8 3  
Gross energy MJ/kg DM 19.6 1.3 18.1 20.4 3 *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 2.9 1.1 1.0 5.4 31  
Phosphorus g/kg DM 13.1 2.4 9.6 20.0 34  
Sodium g/kg DM 1.8 1.2 0.4 3.7 6  
Magnesium g/kg DM 2.4       1  
Manganese mg/kg DM 34 18 7 43 4  
Zinc mg/kg DM 114 44 55 154 5  
Copper mg/kg DM 23 33 1 80 5  
Iron mg/kg DM 78 44 27 107 3  
               
Amino acids Unit Avg SD Min Max Nb  
Alanine % protein 5.9 1.2 4.3 6.9 4  
Arginine % protein 4.4 0.7 3.6 5.2 6  
Aspartic acid % protein 9.0 2.2 7.7 12.2 4  
Cystine % protein 0.9 0.6 0.5 1.9 5  
Glutamic acid % protein 14.7 2.2 11.4 15.8 4  
Glycine % protein 4.0 0.3 3.7 4.3 4  
Histidine % protein 2.0 0.4 1.7 2.9 6  
Isoleucine % protein 4.6 0.8 4.0 6.1 6  
Leucine % protein 6.2 0.8 5.3 7.1 6  
Lysine % protein 6.3 0.9 4.6 7.6 12  
Methionine % protein 1.5 0.3 1.3 2.2 8  
Phenylalanine % protein 3.6 0.4 3.1 4.1 6  
Proline % protein 3.4       1  
Serine % protein 4.3 0.2 4.1 4.5 4  
Threonine % protein 4.4 0.7 3.7 5.6 6  
Tryptophan % protein 1.1 0.2 1.0 1.4 5  
Tyrosine % protein 2.7 0.1 2.5 2.8 4  
Valine % protein 4.9 0.5 4.5 5.8 6  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 89.7         *
Energy digestibility, ruminants % 89.7         *
DE ruminants MJ/kg DM 17.6         *
ME ruminants MJ/kg DM 13.4         *
Nitrogen digestibility, ruminants % 79.5         *
               
Pig nutritive values Unit Avg SD Min Max Nb  
Energy digestibility, growing pig % 87.2         *
DE growing pig MJ/kg DM 17.1         *
MEn growing pig MJ/kg DM 15.9         *
NE growing pig MJ/kg DM 10.4         *
Nitrogen digestibility, growing pig % 84.3       1  
               
Poultry nutritive values Unit Avg SD Min Max Nb  
AMEn broiler MJ/kg DM 9.3       1  
               
Fish nutritive values Unit Avg SD Min Max Nb  
DE salmonids MJ/kg DM 13.7   12.8 13.9 2 *
Energy digestibility, salmonids % 69.7   62.6 76.8 2  
Nitrogen digestibility, salmonids % 77.1   63.2 91.0 2  

The asterisk * indicates that the average value was obtained by an equation.

References

AFZ, 2011; CIRAD, 2008; Dewar, 1967; DLG, 1961; Kuan et al., 1982; Nwokolo, 1986; Piras et al., 1995; Rumsey et al., 1991; Sosulki et al., 1990; Williams, 1955

Last updated on 24/09/2016 18:04:57

References
References 
Datasheet citation 

Heuzé V., Thiollet H., Tran G., Edouard N., Lessire M., Lebas F., 2017. Brewers yeast. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://feedipedia.org/node/72 Last updated on June 2, 2017, 10:29

English correction by Tim Smith (Animal Science consultant)
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