Subacute ruminal acidosis and the relationship with the detection of ruminal acidosis in milk based on milk-fat content, other milk production parameters and nutritional aspects in dairy cows

Abstract

Background: Subacute ruminal acidosis (SARA) is a pathologic condition that is described as impaired ruminal health in which a reversible pH depression occurs. Detection of ruminal acidosis in milk is based on a low milk-fat content. However, clinical symptoms of SARA are important in determining the diagnosis of SARA, because a low ruminal pH or a low milk-fat content does not always mean that a cow is really suffering from SARA. In order to evaluate the detection of ruminal acidosis in milk, clinical examination of 12 early postpartum cows was performed on each of the 26 farms, on the same day as milk test sampling to determine if cows were showing clinical symptoms of SARA. Clinical parameters which were observed were level of consciousness, filling of the rumen, number and strength of ruminal contractions, fecal aspects, ruminating activity and concentrate-intake. Based on this clinical examination, all examinated cows were divided in two groups; SARA or no SARA. Expected and actual milk yield, milk fat content, milk protein content, fat/protein and fat-protein were milk recording data that were used and compared between cows with and without SARA to investigate which milk-production parameters are useful for indicating SARA in dairy cows. The relationship between SARA and feeding grass silage with a high digestibility was also investigated. 13 farms were feeding grass silage with a high digestibility, according to Near-Infrared Spectroscopy (NIRS) by a routine lab, as major forage, The other 13 farms were feeding grass silage with an average digestibility. Consequently, the risk of feeding a highly fermentable diet could be evaluated, because feeding this type of diet provides energy precursors needed for high milk production and to restore a possibly present negative energy balance, but may increase the risk of SARA. The goals of this study were to evaluate the risk of feeding grass silage with a high digestibility and to investigate whether milk-production parameters can be useful for detection of SARA in milk of dairy cows. Results: SARA was not significantly (P>0.05) associated with one of the milk production parameters. Significant differences in the prevalence of SARA between both groups of farms based on the digestibility of grass silage, were not found. Conclusions: Milk-fat content is not reliable for determining SARA. Other milk production parameters are also not indicative for SARA. Feeding a high digestible diet is one of the risks for developing SARA. However, the prevalence of SARA was not significantly higher on farms feeding a high digestible grass silage. On these farms, useful measures were applied to reduce the risk of SARA.