Subacute rumen acidosis in lactating cows: an investigation in intensive Italian dairy herds

Subacute rumen acidosis (SARA) represents one of the most important metabolic disorders in intensive dairy farms that affects rumen fermen- tations, animal welfare, productivity and farm profitability. The aim of the present study was to study the occurrence of SARA in intensive Ital- ian dairy herds and to determine the relationship between diet composi- tion, ruminal pH and short chain fatty acids (SCFA) concentration. Ten commercial dairy herds were investigated; twelve cows in each herd were selected randomly among animal without clinical signs of disease, with good body condition and between 5 and 60 day-in-milk (DIM), to perform rumenocentesis and obtain rumen fluid. Ruminal pH was deter- mined immediately after sampling and concentration of SCFA in rumi- nal fluid was determined on samples after storage. An other objective of this research was to study in detail the effects of rumenocentesis on ani- mal health: this study could confirm the extreme validity of this tech- nique as ruminal sampling. Results were subject to anova and correlation analysis using sigma stat 2.03. The results indicated the pres- ence of SARA in three herds (more than 33% cows with rumen pH < 5.5), a critical situation (more than 33% cows with rumen pH < 5.8) in five farms and a normal rumen pH condition in two herds. In particular, dairy herds show on average SCFA concentration of 150, 145, 123 mmol/l for low pH, critical pH and normal pH herds respec- tively. There were not significant differences among diet composition even if herds with SARA showed a light discordance between initially chemistry composition and residual feed. In the affected herds it was not possible to understand the exact causes of SARA. Animal manage- ment seems to be one of the most important factors in developing SARA including total mixed ration preparation.