The definition of acidosis in dairy herds predominantly fed on pasture and concentrates.
This cross-sectional survey examined the prevalence of ruminal acidosis and the effects of acidosis on the production of dairy cattle. Eight fresh cows, 3 primiparous and 5 multiparous (< 100 d in milk), were selected randomly from each of 100 dairy herds in 5 regions of Australia. Rumen fluid was obtained from each cow by rumenocentesis and a stomach tube, and samples were tested for pH. Stomach tube rumen fluid samples were analyzed for volatile fatty acid, ammonia, and D-lactate concentrations. On the basis of the results of all assays, cows were categorized into 3 distinct categories (categories 1, 2, and 3) by cluster analysis. The percentages of cattle in categories 1, 2, and 3 were 10.2, 29.9, and 59.9%, respectively. Mean rumen pH for categories 1, 2, and 3 were 5.74 +/- 0.47, 6.18 +/- 0.44, and 6.33 +/- 0.43, respectively. Biochemically, categories 1, 2, and 3 were characterized, respectively, as follows: mean total VFA concentration (mM), 100.74 +/- 23.22, 94.79 +/- 18.13, and 62.81 +/- 15.65; mean ammonia concentration (mM), 2.46 +/- 2.02, 7.79 +/- 3.75, and 3.64 +/- 2.03; and mean D-lactate concentration (mM), 0.34 +/- 0.86, 0.28 +/- 0.97, and 0.12 +/- 0.51. Category 1 cows had higher propionate, valerate, isovalerate, and caproate concentrations and were of lower parity than cows in other categories. Cows in category 1 had higher milk production but lower milk fat content than category 2 cows. Herds were assigned to 1 of 3 groups according to the numbers of cows assigned to each category. Herds with > or = 3 of the 8 cows in category 1 were classified as acidotic. Herds with > or = 3 of the 8 cows in category 2 were classified as having suboptimal rumen function, and herds with > or = 3 of the 8 cows in category 3 were classified as normal. Herds that had 3 or more of the 8 cows in category 1 (acidotic herds) had diets with higher energy and nonfiber carbohydrate contents and a lower neutral detergent fiber content than herds with a high prevalence of category 2 or 3 cows. The lack of significance of a herd effect in the statistical models developed suggests that the categories were robust across production systems, in which diets varied from all pasture to total mixed rations. A point prevalence of 10% (95% credible interval, 8 to 12%) of cows with an acidotic profile indicates a high risk for acidosis in the cattle sampled. The higher nonfiber carbohydrate and lower neutral detergent fiber contents of diets for herds with a high prevalence of category 1 cows (acidotic herds) indicates that there may be opportunities to reduce the risk of acidosis by dietary manipulation.
Bramley
E
E
Faculty of Veterinary Science, University of Sydney, Camden, New South Wales 2570, Australia. ebramley@wirefree.net.au
Lean
I J
IJ
Fulkerson
W J
WJ
Stevenson
M A
MA
Rabiee
A R
AR
Costa
N D
ND
D000138:Acidosis / Q000453:epidemiology / Q000378:metabolism / Q000662:veterinary*; D000641:Ammonia / Q000032:analysis; D000821:Animal Feed; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000378:metabolism*; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005260:Female; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000032:analysis; D016014:Linear Models; D009517:New South Wales / Q000453:epidemiology; D012417:Rumen / Q000378:metabolism*; D013272:Stomach Diseases / Q000453:epidemiology / Q000378:metabolism / Q000662:veterinary*; D011795:Surveys and Questionnaires; D014739:Victoria / Q000453:epidemiology
D005232:Fatty Acids, Volatile; D019344:Lactic Acid; D000641:Ammonia