Background last update:6 Aug 2012

Probiotic yeast in small ruminants

The benefits of probiotic live yeast in catt le are well understood and supported by many papers and research trials. Until now, limited research has been performed in small ruminants. Recent Trials show the effect of ruminant specific live yeast on performance, health status and milk production in dairy goats and sheep.

By Eric Chevaux and Marina Mazzia-Fabre
Dairy goats and ewes represent an important fraction of the animal production chain in many south European and Middle Eastern regions, with high value milk mainly destined to the local cheese industry. According to the FAO, the worldwide goat livestock has increased by approximately 50% in the last 20 years, reaching over 800 million in 2005. Dairy goat production has intensified - farmers are now facing the same kind of problems commonly experienced by dairy cow farmers (e.g. acidosis). The same accounts for sheep farmers with producers becoming more concerned about increasing value of their forages while preserving milk quality and hygiene, as well as animal health and longevity, to ensure optimal revenue.
Effect on milk yield
From the experiences of live yeast in dairy cows it is hypothesised that live yeast could also have an effect on performances and health status of small dairy ruminants. To confirm this hypothesis, 10 independent trials involving over 1,000 goats were set up. The ruminant-specific yeast strain Sacharromyces cerevisiae I-1077* was added to the goat's diet. On average, milk yield is significantly increased by 9% (ranging from +4% to +15%), with up to 260g/head/day extra milk produced (Figure 1). Most importantly, this increase did not lead to a decrease in milk quality; fat and protein contents remained unchanged, resulting in an overall increase of total fat and protein yield when live yeast was supplemented. This extra milk yield had no negative impact on either body score condition or plasma metabolites contents, as shown by Stella et al. (2007). The same conclusions were drawn from trials with dairy sheep. By adding yeast to the diet, milk yield was significantly increased without affecting milk quality (fat and protein contents). On average, the milk yield increased by 9% (ranging from +7% to +11%), with up to 200g/head/day extra milk produced (Figure 2 ). The higher milk yield is linked to a better feed efficacy - an average of 7% improvement could be measured.
Animal response to yeast
As shown by the increase in feed efficacy, the effect of yeast on milk yield in both species is most probably linked to better feed utilisation due to the metabolic activity of the yeast in the rumen and its interactions with the rumen microflora; SC I-1077 has been shown to improve fiber digestion and nitrogen metabolism, of which its mode of action is not well described. Other parameters can also play a part in the animal response to the yeast additive: the animal characteristics (genetics, condition, age), the environment (stressors, pathogens) and the diet (type and proportion of fibre, sugars and proteins). This can explain why the observed increase in milk production varied between trials, especially in the case of dairy goats. Indeed, the statistical analysis of ten different trials showed that milk yield response to the yeast correlated with the starch and sugar content of the diet (r2= +0.63). This can be explained by the fact that the richer the diet is in rapidly fermentable carbohydrates (starch and sugars), the higher the risk of subacute acidosis and associated metabolic and performances consequences. In the presence of live yeast, rumen pH is actively controlled and acidosis is prevented. It has been well demonstrated that this is due to the fact that yeast will both efficiently compete with lactate producing bacteria for sugar utilisation and stimulate the growth of lactate utilising bacteria, therefore preventing lactate accumulation and drop in rumen pH.
Added health benefits
Stella et al., (2007) (Milan University) have shown the action of probiotic live yeast on the intestinal ecosystem of early lactating goats. Seventy-two Saanen goats divided into equivalent groups were kept in the same conditions and environment, fed the same basic diet (40% concentrate and triticale silage, hay and dried beet pulp), supplemented or not with live yeast for 105 days, starting 3 weeks after parturition. When the goats received live yeast supplementation, their faecal E.coli population decreased with time, while total Lactobacilli population – the “friendly bacteria” – significantly increased (Figure 3). Interestingly, the number of goats screened positive for E. coli in their faeces also decreased significantly (Figure 4). The total bacterial load, however, was not affected by the treatment. The authors suggest that the increased Lactobacilli level in treated animals may have been responsible for the reduction in levels of the opportunistic pathogen E. coli, not only through pH control but also by competing for receptors at the surface of the gut, thereby improving the stability of the intestinal ecosystem. In addition, knowing that live yeast optimises ruminal digestion, another hypothesis is that the live yeast could help control the lower gut flora balance by limiting the amount of residual nutrients, thus limiting opportunistic microorganism and pathogen development. In both dairy goats and sheep, live yeast supplementation had a positive effect on reducing the somatic cell count. A high somatic cell count is a recurrent problem for most dairy farmers, with direct financial implications. The precise modes of action involved are not yet clear and need further investigation.
Small ruminants can also benefit from ruminant specific live yeast. The main benefits include rumen pH stabilisation in acidosis-prone situations and increased feed utilisation. Current discoveries demonstrate that the benefits are not limited to the rumen but also to balancing the hindgut flora. To reduce the risk of ruminant digestive carriage of human pathogens (Salmonella, E. coli ) is a field of research that should be explored further. More investigations are still underway on these effects and to provide more accurate information to the producer.
Improved cheese-making process
In 2006, Professor Chiofalo of Messina University (Italy) studied the effects of live yeast administration on ewe milk cheese-making capacity, particularly its clotting ability. This trial, between March and June 2006, involved 82, 3-year-old Valle del Belice dairy ewes. At the end of the 85 day trial, the live yeast supplementation gave an extra 290 kg of milk compared to the control diet. For the first time, milk technological parameters were also monitored and showed an improvement in milk curdling properties. When the sheep received live yeast in the diet, milk clotting time significantly decreased (meaning an increased clotting speed) and firmness rate significantly improved. Interestingly, these changes had no negative impact on the curd consistency which was similar between both groups.

*The probiotic yeast strain used in this study, Saccharomyces cerevisiae I-1077 (Levucell SC), is authorised in Europe in dairy cows and bovines (E1711). The small dairy ruminants' authorisation is on-going.
References are available on request.
This article can be found in Feed Mix Magazine Vol. 15. nr. 1

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