Changes

===Laboratory Tests===

===Laboratory Tests===

Measurement of pH in the ruminal fluid of a representative portion of apparently healthy animals in a group has been used to assist in making the diagnosis of subacute ruminal acidosis in dairy herds. Animal selection should be from high-risk groups, eg, in the first 60 days of lactation. Ruminal fluid is collected by rumenocentesis or stomach tube and can be measured in the field using wide-range pH (2-12) indicator paper, although a pH meter yields more accurate results. Twelve or more animals are typically sampled at ~2-4 hr after a grain feeding (in component-fed herds) or 6-10 hr after the first daily total mixed ration feeding. If >25% of the animals tested have a ruminal pH <5.5, then the group is considered to be at high risk of subacute ruminal acidosis. This type of diagnostic tool should be used in conjunction with other factors such as ration evaluation, evaluation of management practices, and identification of health problems on a herd basis.

The diagnosis of subacute rumenal acidosis is aided by the measurement of the pH of rumenal fluid in a sample of animals. Cattle with the highest risk of SARA, i.e. those in early lactation, are selected and rumen fluid is obtained by rumenocentesis or, less commonly, stomach tube. Indicator paper or a pH meter is then used to measure the pH pf the samples. In general twelve animals should be sampled and if greater than 25-30% of the group have a pH less than 5.5, a diagnosis of SARA can be made. In a herd fed a total mixed ration as a single group, it might be useful to sample twelve recently  (14-21 days) calved cows and twelve animals with the maximal dry matter intake (60-80 days calved) in order to evaluate the adequacy of the diet for all animals and to identify at what stage the feeding is problematic. Samples should be taken 6-10 hours after access to fresh TMR, or 2-4 hours after grain feeding in component-fed herds.

 

Milk fat depression is a poor and insensitive indicator of subacute ruminal acidosis in dairy herds. Cows and herds with severe subacute ruminal acidosis may have normal milk fat tests. Thus, it is vitally important not to exclude the diagnosis in a dairy herd that has a normal milk-fat test.  

Milk fat depression is a poor and insensitive indicator of subacute ruminal acidosis in dairy herds. Cows and herds with severe subacute ruminal acidosis may have normal milk fat tests. Thus, it is vitally important not to exclude the diagnosis in a dairy herd that has a normal milk-fat test.  

Cows should be sampled four to

in early lactation? Cows should be sampled four to

eight hours after access to fresh TMR.

eight hours after access to fresh TMR.

Selection of cows in herds managed either on a

Selection of cows in herds managed either on a

period. Cows should be sampled two to three hours after

period. Cows should be sampled two to three hours after

receiving any parlour fed concentrates.

receiving any parlour fed concentrates.

===Other Tests===

===Other Tests===