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Protected yeasts may offer digestion boost to grain fed beef cattle

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An international team of researchers from Canada, China and the UK examined the use of encapsulated and non-encapsulated dried yeast in the diets of beef cattle. The team published its work in the journal of Animal Feed Science and Technology .

“The objective of this study was to determine whether feeding ruminally protected active dried yeast (ADY) exhibits post-ruminal activity in comparison with feeding non-protected ADY assessed by measuring feed intake, ruminal pH and fermentation, and site and extent of feed digestion in finishing heifers,” the researchers said.

The authors said they found feed intake and ruminal digestibility were not altered by the feed additives. However, post-ruminal digestion of organic matter (OM) and neutral detergent fiber (NFD) was improved when encapsulated yeast or both non-encapsulated and encapsulated yeasts were added to the diet.

“The improved digestibility of OM in the intestine appeared to primarily result from the improvement of NDF digestion,” they said. “These results indicate the potential post-ruminal activity of ADY, and benefits to feeding protected yeast on improving intestinal digestibility of nutrients.”

Why focus on yeast supplements?

Adding an antimicrobial as a feed additive to promote growth in high-producing cattle has been a common practice in North America feedlot operations, said the researchers. Monensin is an ionophore often used for that reason.

However, feeding of antibiotics has been scrutinized owing to the concerns around increasing antimicrobial resistance, they said. Finding an inexpensive alternative to antibiotics that maintains end-product quality is of interest.

Probiotics are living microorganisms, often yeast or bacteria, that are considered safe to use in feed. Probiotic yeasts are increasingly fed to ruminants to boost animal health and production efficiency.

Previous research in that area regarding beef cattle production is limited compared to the amount done examining dairy cows, said the researchers. “There is now overwhelming evidence that including probiotic yeasts in dairy cow diets can improve milk production and feed efficiency,” they added.

“Responses attributed to yeast are usually related to stimulation of cellulolytic and lactate-utilizing bacteria in the rumen that help stabilize ruminal pH,” they said. “However, the use of probiotic yeasts to improve beef production has been variable, possibly due to the diet composition, strain of yeast or yeast viability.”

Most work with probiotic yeasts has examined rumen fermentation and areas including stabilizing rumen pH, encouraging growth of lactate-using bacteria, collecting oxygen from ingested feed, improving fiber digestion or promoting growth of ruminal protozoa, they said. Other benefits from adding yeast have also been noted.

Little is known about the influence the live yeast may offer post-rumen, they said. There also is a dearth of research looking at ways to protect live yeast through the rumen so it can reach the lower gut of ruminants, they added.

Methods and materials

In the study, five cannulated heifers were given one of five diets for a period of 21 days before rotating to another of the trial diets, said the researchers. There was a one week adaptation period between each diet.

The diets included a control diet with no ADY or antibiotics; a diet (ANT) with 300 mg monensin and 110mg tylosin/d; a diet (ADY) with 1.5g active dry yeast/d; a feed (EDY) with added encapsulated active dried yeast at 3.5g/d (1.5g ADY and 2g capsule); and a mixed diet (MDY) with 1.5g ADY and 3.5g EDY/d.

ADY was encapsulated using a barley hordein and glutelin from barley grain, they said. Stability of the encapsulated yeast in the rumen was assessed during in vitro examinations.

Cattle received a total mixed ration including barley silage, corn dried distillers grain with solubles, dry rolled barley grain and a vitamin and mineral supplement, said the researchers.

Feed offered and refused were recoded daily, and samples of TMR were collected weekly, they said. Body weights were noted on the first and last day of each diet period, rumen contents were collected on days 19 and 20 and omasal samples were taken on the last four days of each feeding rotation.

Feed intake was established, flows to omasum, nutrient digestibility in the rumen and intestine were determined and microbial nitrogen was recorded, they said. Ruminal pH was checked for days 13-17 of each feeding period.

Results

Dry matter intake was not altered by any of the diets, said the researchers. Ruminal pH, concentration of total volatile fatty acids (VFA), and NH3-N (ammonia) levels were similar for all the diets.

Similarly, no diet altered the flow of organic matter or starch in the omasum were found, they said. Flow of neutral detergent fiber (NDF) was highest with ANT but reduced when EDY was added to the diet.

Molar proportion of acetate and the ratio of acetate to propionate were larger when yeast was added to the diet rather than antibiotics, they said. OM digestion in the rumen tested to be lower when the EDY or MDY diet was fed, but no change in ruminal digestibility of starch or NDF was noted.

However, post-ruminal digestion of OM was found to improve for EDY and MDY diets compared to control and ANT, they said. Digestibility of both NDF and OM in the total digestive tract also improved with EDY or MDY diets.

“These results demonstrate the post-ruminal activity of ADY and indicate the potential of feeding protected yeast to ruminants to increase intestinal digestibility of nutrients,” the researchers said.

No alteration in the flow of nitrogen to the omasum or microbial protein synthesis was found, they said. But digestibility of N for the total digestive tract improved with dietary inclusion of EDY or MDY.

“Supplementation of ADY or MDY tended to have greater gene copy numbers of R. flavefaciens compared with ANT,” they said. “Total protozoa counts were greater in the rumen of heifers supplemented with ADY or MDY compared with control or ANT.”

Source: Animal Feed Science and Technology

Title: Comparison of non-encapsulated and encapsulated active dried yeast on ruminal pH and fermentation, and site and extent of feed digestion in beef heifers fed high-grain diets

DOI: doi.org/10.1016/j.anifeedsci.2017.04.001

Authors: P. Jiao, L. Wei, N. Walker, F. Liu, L. Chen, K. Beauchemin, W. Yang

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