Influence of yeast on rumen fermentation, growth performance and quality of products in ruminants: A review

Abstract

This review aims to give an overview of the efficacy of yeast supplementation on growth performance, rumen pH, rumen microbiota, and their relationship to meat and milk quality in ruminants. The practice of feeding high grain diets to ruminants in an effort to increase growth rate and weight gain usually results in excess deposition of saturated fatty acids in animal products and increased incidence of rumen acidosis. The supplementation of yeast at the right dose and viability level could counteract the acidotic effects of these high grain diets in the rumen and positively modify the fatty acid composition of animal products. Yeast exerts its actions by competing with lactate-producing ( Streptococcus bovis and Lactobacillus ) bacteria for available sugar and encouraging the growth of lactate-utilising bacteria ( Megasphaera elsdenii ). M. elsdenii is known to convert lactate into butyrate and propionate leading to a decrease in the accumulation of lactate thereby resulting in higher rumen pH. Interestingly, this creates a conducive environment for the proliferation of vaccenic acid-producing bacteria ( Butyrivibrio fibrisolvens ) and ciliate protozoa, both of which have been reported to increase the ruminal concentration of trans -11 and cis -9, trans -11-conjugated linoleic acid (CLA) at a pH range between 5.6 and 6.3. The addition of yeast into the diet of ruminants has also been reported to positively modify rumen biohydrogenation pathway to synthesise more of the beneficial biohydrogenation intermediates ( trans - 11 and cis - 9, trans - 11). This implies that more dietary sources of linoleic acid, linolenic acid, and oleic acid along with beneficial biohydrogenation intermediates ( cis -9, trans -11-CLA, and trans -11) would escape complete biohydrogenation in the rumen to be absorbed into milk and meat. However, further studies are required to substantiate our claim. Therefore, techniques like transcriptomics should be employed to identify the mRNA transcript expression levels of genes like stearoyl-CoA desaturase , fatty acid synthase, and elongase of very long chain fatty acids 6 in the muscle. Different strains of yeast need to be tested at different doses and viability levels on the fatty acid profile of animal products as well as its vaccenic acid and rumenic acid composition.

Implication and challenges of direct-fed microbial supplementation to improve ruminant production and health

“…In addition to its potential function in oxygen scavenging [ 71 ], S. cerevisiae has been proved to promote the growth of cellulolytic microbes (e.g., F. succinogenes , R. albus ), LUB (e.g., S. ruminantium ), and amylolytic bacteria (e.g., Ruminobacter , Bifidobacterium ), potentially leading to higher VFA concentration in the rumen after the supplementation [ 72 , 73 ]. This promotion effect may be explained by the fact that S. cerevisiae may provide growth factors, such as organic acids, vitamins, or amino acids, to stimulate ruminal bacterial populations [ 74 ]. The supplementing S. cerevisiae could also lead to improved microbial nitrogen metabolism thus increasing microbial protein flow to the intestine and reducing N loss [ 75 ].…”

“…The supplementing S. cerevisiae could also lead to improved microbial nitrogen metabolism thus increasing microbial protein flow to the intestine and reducing N loss [ 75 ]. Alternatively, the competition with LAB for available sugar can contribute to the potential of SARA alleviation [ 74 ]. However, the persistence and viability of live yeast cells are reported to be low in the rumen since certain strains cannot colonize the rumen for a long period of time [ 76 ].…”

Dietary Supplementation of Yeast Culture Into Pelleted Total Mixed Rations Improves the Growth Performance of Fattening Lambs

“…To solve the problem, YC is supplemented to the diet of dairy cows because of its role in the stabilisation of rumen pH ( 6 , 7 ). YC may have a similar effect on the rumen pH of sheep when fed high-grain diets ( 14 ).…”

Impact of Green Forages in Spring, in the Steppe Regions of Tiaret “Chehaima and Naima”, on the Fatty Acid Composition of the "Biceps Femoris" Muscle of Lambs

“…These meats are rich in polyunsaturated fatty acids (PUFA), and which present relatively simple production processes. Our previous study indicated that the nature of the diet is an essential factor that influences the composition of intramuscular fatty acids (FA) in lambs, whose family FAs n3 are more representative in those fed on steppe plants (Rabah et al, 2019), other studies also confirm the influence of diet on FA (Díaz et al, 2005;Ružić-Muslić, 2012), however, other intrinsic and extrinsic factors may influence and be responsible for the difference in FA such as sex, age, type of breeding, transport to the slaughterhouse, conservation of meat (De Smet et al, 2003 ;Amin and Mao, 2020). Currently, many ruminant breeders tend to modify their feeding practices by reducing the diet based on concentrate, and are now moving more and more to pasture grass which confers little fat in the ruminant carcass compared to that based on concentrate (Daley et al, 2010).…”