November 05, 2018

Interpretive Summary: Using yeast as alternatives to antibiotics in finishing beef steers

Interpretive Summary: Using ruminally protected and nonprotected active dried yeast as alternatives to antibiotics in finishing beef steers: growth performance, carcass traits, blood metabolites, and fecal Escherichia coli.

By: Anne Wallace

Alternatives to antibiotics in animal feed are an important area of study in animal science research. Although antibiotics are effective growth promoters, alternatives are strongly needed. Therefore, the goal of this study, published in the October 2018 Journal of Animal Science, was to evaluate the potential for probiotic yeasts to replace antibiotics in beef steers.

This research evaluated the effects addition of active dried yeast in steer feed had on various aspects of growth and health, compared to antibiotics. Parameters studied included steer growth performance, carcass traits, blood metabolites, and changes to fecal Escherichia coli bacteria.  A total of 75 Angus steers were randomly placed into one of five dietary treatment groups: basal oat and barley control diet (CON), basal diet with antibiotics (ANT), basal diet with active dried yeast (ADY), basal diet with encapsulated dried yeast (EDY), and an ADY + EDY mix (MDY). The feeding period lasted a total of 112 days. Fecal and blood samples were collected on days 0, 56, and 112.

At the end of the treatment period (day 112), results indicated body weights and dry matter intake were not significantly different between the five treatment groups. There was no difference in carcass traits, however carcass quality was poorest in the ANT steers who were noted to have more severely abscessed livers. Blood metabolite differences were as follows: plasma haptoglobin was higher in ADY, EDY and MDY animals, compared to CON and ANT on day 112; serum amyloid A was lower in EDY and MDY and ANT animals compared to CON on day 112; proteins that bind to inflammatory bacterial lipopolysaccharides were higher in the EDY and MDY animals, compared to CON, ANT and ADY on day 56. Blood glucose was also higher in MDY animals on day 112. Finally, fecal bacterial counts of E. coli tended (p=0.06 and 0.07) to be lower in animals fed EDY and MDY compared to ANT, between days 56-112.

The results of this study suggest that probiotic yeasts are an area of interest that needs to be better studied to see if they can effectively function as a replacement for antibiotics in cattle feed. Dr. Wenzhu Z. Yang, corresponding author of the paper, noted that “this is the first time we fed encapsulated live yeast to beef cattle to evaluate its activity in the lower gut. Our study provide[s] a novel deliver[y] method to explore yeast activity in the digestive tract of cattle.” More in-depth studies to better elucidate the effects active dried yeast may have on fecal microbiota and inflammatory blood markers is warranted. The effect of yeasts in conjunction with prebiotics or other probiotics would also be an area of potential interest.

To view the article, “Using ruminally protected and nonprotected active dried yeast as alternatives to antibiotics in finishing beef steers: growth performance, carcass traits, blood metabolites, and fecal Escherichia coli,” visit the Journal of Animal Science.