Technical note: Changes in rumen mucosa thickness measured by transabdominal ultrasound as a noninvasive method to diagnose subacute rumen acidosis in dairy cows

Abstract

Feeding high-grain diets leads to the release and accumulation of short-chain fatty acids in the rumen. The subsequent prolonged decline in ruminal pH can lead to subacute ruminal acidosis (SARA). Accumulation of short-chain fatty acids can cause proliferation of rumen papillae to increase absorption surface, subsequently leading to a thickening of the rumen mucosa. The aim of this study was to evaluate the appropriateness of continuous measurements of the rumen mucosa thickness (RMT) as a diagnostic tool for SARA in dairy cows compared with continuous measurements of ruminal pH. The study used 6 lactating Simmental cows switched from a moderate-grain (MG) diet with 40% concentrate (dry matter basis) for 1 wk to a high-grain (HG) diet with 60% concentrate (dry matter basis) for 4 wk. Reticuloruminal pH was recorded with indwelling sensors throughout the trial. Rumen mucosa thickness was measured by transabdominal ultrasound at 4 d during the MG diet and 23 d during the HG diet. Mean RMT increased from 4.7 ± 0.19 mm in the MG diet to 5.3 ± 0.17 mm in the HG diet, whereas daily mean reticular pH decreased from 6.8 ± 0.01 in the MG diet to 6.5 ± 0.01 in the HG diet. Older cows (>3 lactations) had increased RMT, associated with higher reticular pH throughout the experiment. The higher RMT and pH level in older cows underlines their lesser susceptibility to SARA during high-grain feeding. In conclusion, RMT can successfully be measured using linear ultrasound probes, commonly used by veterinary practitioners as rectal probes. By combining noninvasive RMT measurements with the lactation number of the individual cows in a herd, this study suggests that RMT is a viable option for diagnosing SARA. Further research, using a larger number of cows with different lactations numbers, is needed to establish a cut-off RMT indicating the risk of SARA.

Starch-Rich Diet Induced Rumen Acidosis and Hindgut Dysbiosis in Dairy Cows of Different Lactations

“…For cattle, however, this topic was hardly ever investigated. The absorption capacity of the rumen wall is possibly more efficient in ≥4 L cows, because cows with more than three lactations have a thicker rumen epithelium then cows with three or less lactations [ 13 ]. Together with a bigger rumen, this provides them with potentially a higher number of papillae or larger rumen papillae, resulting in an increased absorptive surface [ 12 ].…”

“…Research in recent years has indicated different susceptibilities to SARA among cows in different lactations [ 10 , 11 ]. One contributing factor to lesser susceptibility is an increase of the rumen-mucosa thickness, and thereby absorptive capacity, with the duration of concentrate feeding and with increased lactation numbers [ 12 , 13 ]. Another major contributing factor is the adaptation of the gut microbiome, of which the rumen and fecal microbiome vary in high and low producing dairy cattle [ 14 , 15 ] and with age [ 16 ].…”

Signals for identifying cows at risk of subacute ruminal acidosis in dairy veterinary practice

“…In general, it is well known that the inclusion of high-concentrate diets causes an enlargement of ruminal papillae length and width (Černík et al, 2011;Zitnan et al, 2003). Recently, it has been suggested that the ruminal mucosa thickness might serve as diagnostic tool for SARA, because the enlargement of the ruminal mucosa can be visualised via transabdominal ultrasound, an equipment which is part of the practical diagnostic tools of veterinarians (Mirmazhari-Anwar, Sharifi, Mirshahi, Mohri, & Grünberg, 2013;Neubauer, Humer, Kröger, Meissl et al, 2017). A pilot study conducted by Mirmazhari-Anwar et al (2013) revealed a negative correlation between the ruminal pH and the ruminal mucosa thickness in bulls fed increasing concentrate levels from 5 to 96%.…”

A retrospective study on transabdominal ultrasound measurements of the rumen wall thickness to evaluate chronic rumen acidosis in beef cattle

“…Although the sample of the animals in the study was considerable, we had investigated just beef cattle of the same sex, breed and stage of breeding, other several variables should be considered seeing if there are differences in RWT and RMST measurements like in dairy cows [21].…”

“…Mirmazhari-Anwar et al (2013) [20] reported increasing rumen mucosa thickness when using a transabdominal rumen ultrasound in cannulated bulls fed diets, increasing in concentrate level from 5 to 96% dry matter (DM). Neubauer et al (2018) [21] confirmed the potential of rumen mucosa thickness measurement via ultrasound as a diagnostic tool for subacute rumen acidosis, adjusted for the age or lactation number of the individual dairy cow.…”