Ex vivo fermentation of hay and corn by rumen bacteria from cattle and sheep

Authors: Weinert-Nelson, Jennifer; ELY, DONALD - University Of Kentucky; Flythe, Michael; Hamilton, Tracy; Ferrell, Jessica; Harlow, Brittany

Submitted to: Fermentation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sheep are often utilized as a model in studies of ruminant animal health and nutrition, and results from cattle and sheep studies are typically referred to interchangeably despite inconsistencies in the current literature regarding utilization of dietary forages and concentrates in these species. Additionally, direct comparative studies evaluating rumen bacteria when animals transition from an all-forage to a high-starch diet are lacking. Therefore, the objective of this study was to compare ex vivo fermentation of hay and corn by rumen bacteria harvested from forage-fed cattle and sheep. Overall, this study demonstrated that the microbial community of cattle and sheep differs both in composition and function, resulting in differential capacities to utilize common dietary feed ingredients. Specifically, there were marked differences in the response of the rumen microbiota of forage-fed cattle and sheep to sudden availability of a high-starch feed substrate. Results of this study indicate the rumen microbiota of cattle may be more sensitive to the introduction of corn, whereas the rumen microbial community of sheep may be more resistant to such a dietary insult.

Technical Abstract: Aims: The objective was to evaluate ex vivo fermentation of hay, corn, and their combinations (2:1; 1:2) by rumen bacteria of forage-fed cattle and sheep. Methods and Results: When bovine and ovine rumen cell suspensions (n = 3 species-1) were incubated (24 h, 39°C) with ground hay, lactate was fully utilized by 24 h and pH did not differ between species. When fermenting ground corn only, digestibility, lactate accumulation, and consequent pH decline was greater in bovine than ovine suspensions. While amylolytic bacteria were 10-fold greater in bovine suspensions fermenting corn at 24 h, Streptococcus bovis were identified as the predominant bacteria regardless of species. Lactate-utilizing bacteria proliferated 1,000-fold in bovine suspensions, while ovine lactate-utilizers remained at baseline levels. However, total volatile fatty acids in corn fermentations did not differ between species. Conclusions: These results indicate that rumen microbial communities of cattle and sheep vary in composition and function, resulting in differential capacities to utilize common feed ingredients. Significance and Impact of the Study: Potential differences in rumen acidosis susceptibility exist between species. However, future research is needed to confirm these species differences in vivo.