Specimens: Serum or plasma
Optimum number of animals to test for mob/herd/flock: 8-10
Collection protocol: Samples must be submitted chilled and tested within 2 days of collection.
General information about the test: NEFA’s is useful for detecting cows in negative energy balance (when body fat is being mobilised) 2-14 days before calving and perhaps colostrum cows. Avoid testing cows that are on the point of calving. Outside these times it has limited use. Diurnal variation in serum concentrations of NEFA can occur and their lowest concentration is reached 4-5 hours after feeding so blood for testing should collected just before feeding to obtain peak concentrations.
Reference interval (Cattle): Optimum concentration for milking cows: <1.0 mmol/L although some studies have found that normal values for cows in positive energy balance can be as low as <0.2 mmol/L