Testing the Effects of a High-Grain Diet on Cows with HPLC

A recent study (1) published in Microbiology Spectrum, explored the dynamics of immune gene expression, ruminal metabolome, and gut microbiota in cows due to the duration of high grain feeding. The scientists used high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) and anion-exchange (AEX) chromatography to evaluate the Rumen metabolome of the cows. This work could shed new light on host response and microbial dynamics in parallel, the scientists wrote.

The ruminant digestive tract comprises four-chambered stomachs degrading and processing the diet ingested by animals (2). This process depends on predominantly anaerobic microorganisms inside the rumen responsible for breaking down a variety of feed particles into digestible nutrients, such as ß-linked carbohydrates into digestible sugars (3). Fermentation of these nutrients by ruminal microorganisms is advantageous to their growth and proliferation and provides significant precursors for the host's metabolic pathways (4).

The authors state that it has been generally perceived that during a diet transition in cattle, major changes occur regarding microbial profiles, gastrointestinal fermentation, and expression of genes associated with nutrient utilization. This timeframe has therefore been suggested to be highly risky for cattle health. While the evaluation of the effect of increased duration of high-grain feeding on microbial and immune changes is crucial to understand the time needed for animal adjustment to a diet change, the microbial- and immune-related changes due to the increased duration of high-grain feeding after the diet transition remain poorly understood, thus representing important research gaps that need to be addressed.

The researchers set out to evaluate the effect of duration of high-grain feeding on the dynamics of ruminal and hindgut microbiota, ruminal metabolome, and expression of inflammation-associated genes focusing on the nuclear factor-kappaB (NFkB) pathway, deemed as one of the major triggers for the development of rumenitis in association with subacute ruminal acidosis. Additionally, the team aimed to evaluate correlations between the host immune response and the changes in the gut microbiota composition, hypothesizing that after the gradual diet transition, a 4-week period of high-grain feeding would be enough for cows’ gastrointestinal tract microbiome and immune response to completely adjust to the diet.

Nine ruminally cannulated, non-lactating, multiparous Holstein cows were used. Water and feed were available for ad libitum consumption. The experiment consisted of two periods, with an interval of two months between them A portion of the ruminal fluid collected was analyzed for metabolic profile. This analysis on ruminal fluid was performed by anion exchange chromatography coupled to high-resolution mass spectrometry; in addition, biogenic amines (alpha-aminobutyric acid, aminovaleric acid, beta-alanine, cadaverine, ethanolamine, gamma-aminobutyric-acid, histamine, putrescine, phenylethylamine, pyrrolidine, spermidine, spermine) were measured by liquid chromatography tandem mass spectrometry (LC-MS/MS).

The researchers conclude that the transition to a high-grain diet initiates a significant reduction in rumen microbial alpha diversity, leading to stabilization by the third week of the diet. Despite this initial stabilization, this feeding period is characterized by persistent alterations in microbial relative abundance, metabolic pathway activities, and the expression patterns of signaling receptors, mediators, and targets associated with the NFκB pathway. The research team believes that their findings underscore the critical adaptation period of at least four weeks required by cows after the transition to high-grain feed and provide pivotal insights for designing and interpreting experiments that involve dietary modifications in cattle, highlighting the need for adequate adjustment periods to ensure the stability and reliability of research outcomes.

Holstein dairy cow grazing in a green pasture with its herd in the background. © gozoli - stock.adobe.com

References

1. Castillo-Lopez, E.; Ricci, S.; Rivera-Chacon, R.; Sener-Aydemir, A.; Pacífico, C.; Reisinger, N.; Schwartz-Zimmermann, H. E.; Berthiller, F.; Kreuzer-Redmer, S.; Zebeli, Q. Dynamic Interplay of Immune Response, Metabolome, and Microbiota in Cows During High-Grain Feeding: Insights from Multi-Omics Analysis. Microbiol, Spectr. 2024, 0:e00944-24. DOI: 10.1128/spectrum.00944-24

2. Harfoot, C. G. Anatomy, Physiology and Microbiology of the Ruminant Digestive tract. Lipid Metab. Rumin. Anim. 1981. DOI: 10.1016/0079-6832(78)90003-4

3. McAllister, T. A.; Bae, H. D.; Jones, G. A.; Cheng K. J. Microbial Attachment and Feed Digestion in the Rumen. J. Anim. Sci. 1994, 72, 3004–3018. DOI: 10.2527/1994.72113004x

4.

Hungate, R. E. The Rumen and Its Microbes; Academic Press, 1966.