Managing metabolic health in transition dairy cows is challenging. Many factors such as body condition, length of previous lactation, stocking density, heat stress, stall design, and ration composition combine to influence metabolic status and health. Monitoring serum concentrations of key metabolites can aid in assessing and managing metabolic health in dairy cows.
The Nutrition Section offers individual tests for non-esterified fatty acids (NEFA) and beta-hydroxybutyric acid (BHB), as well as a metabolic profile panel that adds albumin, urea nitrogen, and aspartate aminotransferase (AST) to NEFA and BHB. Energy balance is reflected by NEFA concentrations, which may be determined on both pre-partum (“close-up”) cows as well as fresh cows. Subclinical ketosis is reflected by serum BHB concentrations, which are generally only useful in fresh cows. The metabolic profile adds variables to estimate protein status and severity of liver fat deposition.
NEFA concentrations reflect the energy status of the animal, with high concentrations indicating negative energy balance. Negative energy balance and high serum NEFA concentrations are risk factors for metabolic disease in dairy cows. Testing serum NEFA concentrations is particularly useful in evaluating dry cow management and nutrition in dairy herds, but is also valuable in assessing energy status of cows in early lactation. Samples for NEFA testing may be either serum or EDTA plasma. They should be collected from a minimum of seven animals from each feeding or gestation/lactation group. The results are most useful if the samples are taken just before fresh feed is offered. Blood NEFA concentrations are elevated by excitement, so cows should be agitated as little as possible during the sample collection process. When gang locks are available, a useful protocol is to lock up the animals immediately after fresh feed is offered and to collect the samples before they’ve had a chance to consume much feed.
BHB Concentrations Compared to Serum NEFA Concentrations
Serum BHB concentrations are very seldom elevated in cows before calving, so BHB is of little usefulness in the evaluation of dry cow nutrition or metabolic status. Use serum NEFA when evaluating dry and close-up cow groups. After calving, both serum BHB and NEFA can be useful in evaluating nutritional status. Serum NEFA is a direct indication of energy balance with NEFA concentrations increasing as negative energy balance becomes more severe. Serum BHB concentrations are indicators of the metabolic response cows are making to negative energy balance. High serum concentrations of serum BHB in clinically normal cows indicate subclinical ketosis, which is associated with reduced fertility and milk production, as well as increased risk for clinical ketosis and displaced abomasum.
Collecting and Submitting Samples
Metabolic monitoring is done on a herd-level basis, thus testing multiple animals is necessary. Seven to twelve animals should be tested from each group for which an evaluation is desired, i.e. seven to twelve “close-up” cows and a similar number of fresh cows. Blood samples should be collected into clot (red-top) tubes. The best time for sampling is just prior to or at the time of feeding. Excessive excitement should be avoided. Serum should be separated from the clot within four hours of collection and the samples sent to the laboratory on ice via an overnight courier service.