A Grain-Based SARA Challenge Affects the Composition of Epimural and Mucosa-Associated Bacterial Communities throughout the Digestive Tract of Dairy Cows.

The effects of a subacute ruminal acidosis (SARA) challenge on the composition of epimural and mucosa-associated bacterial communities throughout the digestive tract were determined in eight non-lactating Holstein cows. Treatments included feeding a control diet containing 19.6% dry matter (DM) starch and a SARA-challenge diet containing 33.3% DM starch for two days after a 4-day grain step-up. Subsequently, epithelial samples from the rumen and mucosa samples from the duodenum, proximal, middle and distal jejunum, ileum, cecum and colon were collected. Extracted DNA from these samples were analyzed using MiSeq Illumina sequencing of the V4 region of the 16S rRNA gene. Distinct clustering patterns for each diet existed for all sites. The SARA challenge decreased microbial diversity at all sites, with the exception of the middle jejunum. The SARA challenge also affected the relative abundances of several major phyla and genera at all sites but the magnitude of these effects differed among sites. In the rumen and colon, the largest effects were an increase in the relative abundance of Firmicutes and a reduction of Bacteroidetes. In the small intestine, the largest effect was an increase in the relative abundance of Actinobacteria. The grain-based SARA challenge conducted in this study did not only affect the composition and cause dysbiosis of epimural microbiota in the rumen, it also affected the mucosa-associated microbiota in the intestines. To assess the extent of this dysbiosis, its effects on the functionality of these microbiota must be determined in future.

Changes in Microbiota in Rumen Digesta and Feces Due to a Grain-Based Subacute Ruminal Acidosis (SARA) Challenge.

The effects of a grain-based subacute ruminal acidosis (SARA) challenge on bacteria in the rumen and feces of lactating dairy cows were determined. Six lactating, rumen-cannulated Danish Holstein cows were used in a cross-over study with two periods. Periods included two cows on a control diet and two cows on a SARA challenge. The control diet was a total mixed ration containing 45.5% dry matter (DM), 43.8% DM neutral detergent fiber, and 19.6% DM starch. The SARA challenge was conducted by gradually substituting the control diet with pellets containing 50% wheat and 50% barley over 3 days to reach a diet containing 55.6% DM, 31.3% DM neutral detergent fiber, and 31.8% DM starch, which was fed for four more days. Rumen fluid samples were collected at day 7 and 10 of experimental periods. Feces samples were collected on days 8 and 10 of these periods. Extracted DNA from the rumen and feces samples was analyzed to assess their bacterial communities using MiSeq Illumina sequencing of the V4 region of the 16S rRNA gene. The induction of SARA reduced the richness, diversity, and stability of bacterial communities and resulted in distinctly different microbiota in the rumen and feces. Bacteroidetes and Firmicutes were the most abundant phyla and, combined, they represented 76.9 and 94.4% of the bacterial community in the rumen fluid and the feces, respectively. Only the relative abundance of Firmicutes in the rumen was increased by the SARA challenge. In rumen fluid and feces, the abundances of nine out of the 90 and 25 out of the 89 taxa, respectively, were affected by the challenge. Hence, SARA challenge altered the composition of the bacterial community at the lower taxonomical level in the feces and therefore also likely in the hindgut, as well as in the rumen. However, only reductions in the bacterial richness and diversity in the rumen fluid and feces were in agreement with those of other studies and had a biological basis. Although the composition of the bacterial community of the feces was affected by the SARA challenge, bacterial taxa in the feces that can be used for accurate and non-invasive diagnosis of SARA could not be identified.

Indicators of induced subacute ruminal acidosis (SARA) in Danish Holstein cows.

BACKGROUND: The prevalence of subacute ruminal acidosis (SARA) in dairy cows is high with large impact on economy and welfare. Its current field diagnosis is based on point ruminal pH measurements by oral probe or rumenocentesis. These techniques are invasive and inaccurate, and better markers for the diagnosis of SARA are needed. The goal of this study was to evaluate clinical signs of SARA and to investigate the use of blood, faecal and urinary parameters as indicators of SARA. Six lactating, rumen cannulated, Danish Holstein cows were used in a cross-over study with three periods. The first and second periods included two cows on control diet and two cows on nutritional SARA challenge. The third period only included two cows on SARA challenge. Control diet was a conventional total mixed ration [45.5% dry matter (DM), 17.8% crude protein, 43.8% neutral detergent fibre, and 22.5% acid detergent fibre (DM basis)]. SARA challenge was conducted by substituting control diet with grain pellets (50% wheat/barley) over 3 days to reach 40% grain in the diet. Ruminal pH was measured continuously. Blood samples were collected once daily at 7 h after feeding. Samples of faeces and urine were collected at feeding, and at 7 and 12 h after feeding. Blood samples were analysed for pCO2, pO2, pH, electrolytes, lactate, glucose, packed cell volume (PCV), and total plasma protein concentration. Milk composition, ruminal VFA, and pH of faeces and urine were measured. RESULTS: SARA was associated with decreased (P < 0.05) minimum ruminal, faecal and urinary pH. Daily times and areas of ruminal pH below 5.8, and 5.6 were increased to levels representative for SARA. Significant differences were detected in milk composition and ruminal VFAs. Blood calcium concentration was decreased (P < 0.05), and pCO2 tended to be increased (P = 0.10). Significant differences were not detected in other parameters. CONCLUSIONS: SARA challenge was associated with changes in faecal and urinary pH, blood calcium concentration and pCO2. These may be helpful as indicators of SARA. However changes were small, and diurnal variations were present. None of these parameters are able to stand alone as indicators of SARA.

Proteomics: a new tool in bovine claw disease research.

Claw horn disruption (CHD) is a common underlying cause of lameness in dairy cattle which leads to compromised animal welfare and production losses. Despite an intense research effort over the last two decades, progress in reducing the prevalence of lameness due to CHD has been limited. In addition to current research strategies there is a need to develop novel approaches and methods that expand understanding of the disease mechanisms involved in CHD. The objectives of the present study were to explore the potential of liquid chromatography tandem mass spectrometry (LC-MS/MS) in mapping protein expression in three different bovine claw tissues, and to provide a relevant functional annotation of the proteins characterized in these tissues. LC-MS/MS was used to characterize protein expression in coronary band skin (C), claw dermal (D) and lamellar (L) tissues from two heifers. A total of 388 different proteins were identified, with 146 proteins available for identification in C, 279 proteins in D and 269 proteins in L. A functional annotation of the identified proteins was obtained using the on-line Blast2GO tool. Three hundred and sixteen of the identified proteins could be subsequently grouped manually to one or more of five major functional groups related to metabolism, cell structure, immunity, apoptosis and angiogenesis. These were chosen to represent basic cell functions and biological processes potentially involved in the pathogenesis of CHD. The LC-MS/MS-based proteomic analysis presented here is the largest published survey, so far, of the bovine claw tissue proteome.