Subclinical ruminal acidosis and associated pathological findings in dairy cows.

In dairy cows, one of the most frequent metabolic disorders that occurs is the subclinical ruminal acidosis (SRA). In this work biochemical changes in ruminal fluid and urine were determined to establish the frequency of this disturbance with respect to reproduction cycle. There were sampled 150 cows with high milk production in a large dairy complex. Cows were divided into 3 groups according to their reproduction period in the following way: Group 1, (n=50) 4 - 8 weeks postpartum (mean milk production 32.4 kg/day); group 2 (n=50) 5 months postpartum (mean production 24.1 kg/day); group 3 (n=50) 7 months pospartum (mean production 15 kg/day). The lactation period diet consisted of corn silage, alfalfa and concentrates (30 - 60% dry metter) according to production. Pathological findings were obtained in postmortem studies in 345 animals which had died because of different causes. In group I, ruminal pH was 5.90 +/- 0.48, oxide-reduction of methylene blue (ORMB) in minutes was 4.5 +/- 2.3, protozoa count (PC)(x10(3) /ml) was 163.8 +/- 53.6. In group 2, pH was 6.28 +/- 0.56, ORMB was 5.7 +/- 2.1 and PC was 200.6 +/- 66.4. In group 3 pH was 6.67 +/- 0.28, ORMB was 6.6 +/- 2.0 and PC was 260.5 +/- 82.0. The frequency of SRA observed in groups 1, 2 and 3 was 36%, 16% and 2% respectively. Aciduria was detected in 40% for group 1, 18% in group 2 and 4% in group 3. Ketonuria was detected in 6% in group 1, negative in groups 2 and 3. Proteinuria was observed in 6%, 4% and 2% for groups 1,2 and 3 respectively. pathological findings were: 51.88% (n = 179) in digestive tract and 28.98% (n = 100) in respiratory system. Most important lesion related to ruminal acidosis were parakeratosis rumenitis and abscedative hepatitis (24.9% of 345 cases), thrombosis of caudal vena caval and thromboembolic pneumonia (14.5% of 345 cases). For diagnosis of SRA in practical conditions is Very important to integrate anamnesis (including diet composition), clinical examination, ruminal fluid and urine tests, together with postmortem observation if possible.