Yeast (Saccharomyces cerevisiae) as a Feed Additive for Feedlot Cattle

Published: February 13, 2023

By: M.S. Williams 1, O. AlZahal 2, I.B. Mandell 1, B.W. McBride 1, G.B. Penner 3, M. Steele 1, and K.M. Wood 1 / 1 Department of Animal Biosciences, University of Guelph, Guelph, ON; 2 AlZahal Innovation & Nutrition, Kitchener, ON; 3 College of Agriculture and Bioresources, University of Saskatoon, Saskatoon, ON.

Summary

Feed additives are derived from many origins and have been used in the animal production industry with increased use in the last three decades due to positive impacts on animal health and performance. With changing consumer demands and concerns of antimicrobial resistance, legislation limited access to in-feed antimicrobials in Canada as of December 2018. This has further increased the interest in other feed additives to improve animal growth, health, and efficiency. Yeast is a natural feed additive available in many forms, strains, and doses for livestock production; however, the majority of research in Saccharomyces cerevisiae yeast supplementation in livestock has focused on dairy cattle. Although modes of action have been proposed, one of particular interest for feedlot cattle is the ability to stabilize ruminal pH. It is postulated that S. cerevisiae aids in reducing lactate accumulation in the rumen by stimulating the production of lactic acid utilizing bacteria, ultimately increasing rumen pH (Chaucheyras-Durand et al., 2008). For feedlot cattle, the late finishing phase is that of greatest risk for ruminal acidosis and subsequent liver abscess, and poor animal performance (Nagaraja and Chengappa, 1998; Castillo-Lopez et al., 2014). Research was conducted on late finishing feedlot cattle that were supplemented with S. cerevisiae (60 billion colony forming units; YST) and compared to those that were not supplemented (CON) to evaluate growth performance, carcass characteristics, and indicators of rumen health (Williams et al., 2021). The results of that experiment suggested that YST decreased carcass characteristics or rumen health (P ≥ 0.07). Although this trial improved feed efficiency, the mechanisms of action of yeast for beef cattle remain unclear. Our future research program aims to increase the understanding of the modes of action of yeast as a direct-fed microbial in high-grain finishing feedlot cattle diets for the improvement of animal performance and health.

Key words: yeast, saccharomyces cerevisiae, feedlot, beef.

Introduction

The Canadian beef industry produces over 1.5 million tonnes of high-quality protein annually while maintaining the highest standards in animal care and environmental sustainability (CCA, 2020). In Canada, access to in-feed antibiotics has been limited to veterinary prescription and growth claims have been removed. To keep up the high standards of efficient production and prudent antimicrobial stewardship in the beef industry, alternative feed additives like yeast require investigation to determine if they may help improve animal health and performance. Further research is required to determine if and how they can replace conventional feed additives.

Although feeding yeast to cattle is not a particularly novel concept, the majority of research has focused on dairy cattle, and responses may differ in high-grain diets. The literature indicates that yeast may help stabilize ruminal pH by reducing lactate accumulation due to high concentrate diets fed to dairy cattle (McAllister et al., 2011). The late finishing phase is the highest risk period for feedlot cattle to experience ruminal acidosis (Castillo-Lopez et al., 2014), and yeast supplementation can potentially mitigate the effects at higher dose rates during this period. Previous research in feedlot cattle indicates that supplementing yeast is promising; however, differences in yeast type and form, diet type, and dosage make comparing results across trials difficult (Buntyn et al., 2016).

An experiment was conducted to assess the impacts of supplemental S. cerevisiae at a high dose in the diet of late finishing cattle on animal performance, feeding behaviour, ruminal pH, ruminal volatile fatty acid concentrations, carcass characteristics, rumen wall morphology, rumen health, and biological markers of immune response and gut barrier function (Williams et al., 2021). Angus cross feedlot steers (n = 51) were fed a corn-based finishing ration for 55 ± 19 days with (YST) or without (CON) 60 billion colony forming units of active-dry S. cerevisiae yeast per day. It was observed that YST steers reduced feed intake (31%) and improved feed efficiency (P ≤ 0.001). A reduction in dry matter intake (DMI) variation was also observed for YST steers compared to CON (P = 0.04). No differences were observed between treatments for average daily gain or ultrasound measurements. Previous research in beef cattle has observed an increase or no change in DMI (Beauchemin et al. 2003b; Vyas et al. 2014; Ran et al. 2018). In addition, in our experiment, we did not observe differences in circulating blood metabolites (P ≥ 0.13); therefore, fat or protein mobilization did not appear to be the reason why YST steers, that consumed much less feed, continued to gain as much as those eating 31% more feed per day. It was speculated that the YST steers may have had improved energy efficiency; one postulated mechanism was through enhanced propionate production. However, although propionate concentration was numerically higher in these steers (YST 37.2 mol/100mol, CON 31.7 mol/100mol; P = 0.23), it was not significantly different. Ruminal pH and time spent in ruminal acidotic states were not different between treatments (P ≥ 0.08) but numerically lower for YST, similarly to previous research (Mohammed et al., 2017); however, not significant (P ≥ 0.08). This may be due to increased animal variation and limited pH sensors in the experiment. No differences were detected between treatments for carcass characteristics, rumen wall morphology, rumen health, or biological markers of immune response (TLR2, TLR4, FCAR) and gut barrier function (OCLN, CLDN, ZO1, ZO2; P ≥ 0.07). These results were expected without differences in weight gain, ruminal kinetics, or a ruminal acidotic challenge. The results of this experiment suggest that the addition of yeast during the late finishing phase in a high-grain diet reduces dry matter intake and its variation without impacting weight gain, carcass characteristics or rumen health, thereby improving feed efficiency. Saccharomyces cerevisiae mechanisms of action are not well understood in beef cattle, and additional work at this higher dose range (60 billion colony forming units) using a similar yeast strain, animal, and diet type are warranted.

Proposed Research Plan

Three experiments have been developed using the same animal type (finishing beef cattle), basal diet composition (corn-based), yeast strain (S. cerevisiae) and dose (60 billion colony forming units). This will allow for a more thorough investigation into impacts and the mode of action of S. cerevisiae in high-grain beef cattle diets. Experiment 1 aims to determine the impact of the form of yeast (active-dry, heat-killed, or rumen-protected) and expected location of the activity against positive (with conventional antimicrobials) and negative (no feed additives) controls on steer performance, total tract digestibility, and ruminal pH. The second experiment will determine the impact of yeast supplementation on gut barrier function and molecular markers of gut permeability and immune response in the gastrointestinal tract of high-grain feed beef cattle. The final experiment aims to determine the impact of yeast on the microbiome of the rumen, jejunum, and colon of beef cattle fed high-grain diets with or without yeast supplementation. The overall hypothesis of this program is that the addition of yeast improves indicators of gut health and metabolic disease, helping to stabilize ruminal pH and improve overall production efficiency when fed to finishing steers. This research can offer significant benefits to the beef cattle industry by reducing metabolic disease, and improving feed efficiency and food safety through reducing livestock's contribution to antimicrobial resistance to medically important antibiotics and evaluating alternatives to antimicrobials.

This work is expected to have immediate benefits to the Canadian beef and feed industries. In addition to the potential reduction in rumen acidosis and liver abscesses, the addition of yeast may have the potential to increase feed efficiency and nutrient digestibility. Improvement in feed efficiency has four times the economic return over the same percent increase in animal performance (Gibb and McAllister, 1999). This research will increase the body of knowledge of direct-fed microbials in the feedlot sector and perhaps deliver a transformative technology to improve animal health and welfare, and improved performance efficiency for the feedlot industry.

Presented at the 2021 Animal Nutrition Conference of Canada. For information on the next edition, click here.

References

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Williams, M. S., O. AlZahal, I. B. Mandell, B. W. McBride, and K. M. Wood. 2021. The impacts of a fibrolytic enzyme additive on digestibility and performance in the grower and early finisher period, and supplemental Saccharomyces cerevisiae on performance and rumen health in the late finisher period for feedlot cattle. Can. J. Anim. Sci. Just-IN.

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