PHOTO: HERBERT WIGGERMAN


YEAST ▶▶▶


Yeast as a feed supplement for cattle


Yeast is a probiotic material that is currently being used in many parts of the world as a feed supplement for livestock. The use of yeast in animal feeding programmes has in many cases resulted in improved rumen fermentation, animal health, milk yield, and adaptation to heat stress.


BY SALAH H. ESMAIL, PHD E


conomically, yeast is a low-cost material compared to other feed supplements and can thus cost-effectively improve the performance of animals. Certain points should, however, be considered when attempting to


make full use of yeast in cattle feeding programs.


Preparing the yeast material The process of producing yeast biomass involves inoculation of a culture media containing products of the sugar refining or cereal grain raw ingredients with live yeast cells. Fermenta- tion of the media takes place in large tanks using microbial strains such as C. cervisia, T. utilis, and C. lypolitica. Once the fermentation media fills the tank, it is harvested by centrifu- gation and allowed to dry. The isolated biomass of yeast is then hydrolysed to release nucleic acids and treated with me- thionine and some flavouring agents containing peptides and minerals. The material is finally incorporated into the cattle’s diet at up to 50 grams per head per day.


Yeast and rumen fermentation Yeast can scavenge oxygen from the rumen, making the eco- system more favorable for the growth and activity of rumen anaerobic microbes. It also can increase cellulolytic activity in the rumen and increases nutrient digestibility, especially for rich fibre diets. Yeasts have also been shown to regulate the rumen pH and limit acidosis risks by regulating both lactate producing and lactate utilising bacteria. A microbial strain such as S. cerevisiae is a rich source of nutrients such as pep- tides, vitamins, organic acids, and cofactors which may be required by the rumen bacteria.


Effect on animal health In a study with dairy calves, it was found that incorporating


12 ▶ ALL ABOUT FEED | Volume 30, No. 5, 2022


yeast culture at 2% of the grain fed from 2 to 70 days of age improved the neutrophil function when the yeast cells were incubated with pathogenic E. coli. Calves fed with yeast tend- ed to have fewer days with mild or watery diarrhoea. Cases of fever per calf were also reduced by feeding yeast culture. Be- cause of the reduced incidence of such health disorders, the proportion of calves treated with anti-inflammatory and an- ti-diarrhoea products was reduced and calves treated with antibiotics tended to be reduced, too (for yeast culture com- pared with control). Net income was higher, approximately US$ 0.48 for calves fed with a yeast culture because of the im- provement in income with calf value. The mortality rate was markedly lower with yeast culture after 13 days of age. Risk of mortality past day 13 was 6-fold less for yeast culture compared to the control.


Effects on milk yield Adding yeast to dairy rations may improve milk production and profitability in dairy cows. This may be attributed to two distinct mechanisms: 1. With yeast supplementation, there are changes in the ru- men microbial population, rumen fermentation, intestinal nutrient flow, and diet digestibility, all of which favour increased milk yield.


2. Yeast products are rich in B vitamins, amino acids, pep- tides, nucleotides, and phenolic compounds that can act alone or in combination as antioxidants, appetite stimu- lants, inhibitors of pathogen colonization, and/or immune nutrients.


In many cases, however, inconsistent responses have been observed. One explanation for this inconsistency is the differ- ences in inclusion level, type of diet fed, feed intake, and the use of additional feed additives, in addition to factors such as age, physiological stage, health, and stress status.


Adaptation to heat stress The effects of yeast supplementation on heat-stressed cows can be summarised as follows: • Improvements in DM intake, lactation performance, and feed efficiency.


• Supplementating with yeast culture reduces the rectal


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36