Transition Cow Energy Metabolite Assessment
Transition cow energy metabolite assessment is frequently used by dairy practitioners to
monitor dairy herds in order to prevent disease and optimize herd health
and productivity. Since the most stressful time (metabolically speaking)
for a cow is the transition period (late pregnancy to early lactation),
most of the monitoring is done in cows during this critical time. Interpretation
of data obtained for herd health monitoring differs from interpreting
data for the purpose of disease diagnosis in individual animals. Abnormal
test results (above or below) with respect to established reference
intervals are used to obtain a diagnosis of disease in individual animals.
For herd level testing, reference intervals are not relevant, rather
the data is interpreted as either the proportion of tested animals with
values above or below a specific cut-off value or as the average value
which is above or below a specific cut-off value. These cut-offs are
determined from research studies that measure statistical assocations
between the analyte of interest and downstream effects. In dairy herd
health, pertinent downstream effects include the incidence of metabolic
(clinical ketosis, displaced abomasum) and infectious/inflammatory (e.g.
metritis, mastitis) diseases in the postparptum period, subsequent reproductive
performance and milk yield.
For herd health testing, it is imperative to sample a sufficient number
of animals to obtain reasonable confidence limits that the sampled group
is a true representative of the herd. Most investigators use 75% confidence
limits; this equates to testing 12 animals in large herds (> 500
cows). Naturally, the more animals sampled, the higher the confidence
intervals, however sampling very large numbers is frequently impractical
and and not cost effective.
Transition cow energy metabolite assessment includes testing both prepartum and postpartum cattle, as indicated below. Studies done at Cornell University (Ospina et al 2010 for diseases, Ospina et al 2010 and Ospina et al 2010 for herd-level testing) for reproductive and milking performance) in dairy herds show that postpartum NEFAs are more predictive of downstream diseases (displaced abomasum, metritis, mastitis) and decreased reproductive performance than prepartum NEFAs or postpartum BHB in dairy herds in the Northeastern USA.
- Measurement of non-esterified fatty acids (NEFAs) in prepartum cows (2-14 days before calving).
- Transition cow energy profile: Measurement of non-esterified fatty acids and β-Hydroxybutyrate (BHB) in the immediate postpartum period (3-14 days in milk).
- We also offfer a "metabolic profile" test for postpartum dairy cows (3-14 days in milk), which includes NEFAs, BHB, albumin, urea and AST (see below).
Sample collection guidelines for transition cow energy metabolite assessment
- Collection tube: A red top tube is recommended for sample collection. Serum should be separated from cells ASAP after collection and the serum placed in a separate tube. Corvac (serum separator) tubes are NOT recommended (values are significantly different in corvac versus red top tubes).
- Time of collection: Collect samples from cows that are 3-14 days in milk. Also sample cows as they are coming into the feeding stalls. Do not overstress cows - NEFAs increase with stress or excitement.
- Sample storage: Samples MUST be kept cool to minimize false changes in results (NEFAs are particularly unstable). Submit ASAP to the laboratory.
- Number of cows: A minimum of 12 animals per herd should be sampled for herd level testing. This can be a mixture of heifers and >2 parity cows.
- Pooled samples: Pooling of individual samples from cows to assess energy status of a herd is NOT recommended. Studies at Cornell University have shown that results from pooled samples are insensitive when using prepartum NEFA, postpartum NEFA or postpartum BHB for the detection of excessive negative energy balance in transition dairy cows.
- NEFA: NEFAs are a biomarker of
negative energy balance. NEFA concentrations are interpreted as the
proportion of animals above a specific cut-off value. Based on studies done at Cornell University in total mixed ration (TMR)-fed dairy cows, we interpret results as follows:
- For individual dairy cows, there is an increased incidence
of postcalving diseases (displaced abomasum, metritis/retained placenta
and clinical ketosis), decreased milk yield and decreased reproductive performance in the first 30 days in milk in Holstein dairy
cows with NEFA values > 0.60-0.70 mEq/L when tested 3-14 days after calving.
- At the herd-level, there is a significantly increased risk of post-calving metabolic and infectious diseases, decreased milk production or decreased reproductive
performance if >15-20% of tested postcalving cows have NEFA values > 0.70 mEq/L.
(BHB): BHB is used
as a marker of subclinical ketosis and values are interpreted similarly
- For individual dairy cows, a post-calving BHB > 10 mg/dL is associated with a significant risk of post-calving metabolic or infectious diseases (displaced abomasum, clinical ketosis and metritis), decreased milk yield and decreased reproductive performance in individual TMR-fed Holstein cows.
- At the herd-level, there is a significantly increased risk of these post-calving diseases, decreased milk production or decreased reproductive performance if >10% of tested post-calving cows have BHB values > 10 mg/dL.
- AST: This hepatocellular leakage
enzyme is used as a marker of underlying hepatic lipidosis. However,
AST is not specific for liver and will be increased with skeletal
muscle injury. In addition, it does not appear to be a very sensitive
test for lipidosis in dairy cows. Alternatives to AST include GLDH, which is more stable than SDH (both SDH and GLDH are markers of liver injury).
- Urea: This is a reflection
of the ammonia concentration in the rumen and the protein (and energy)
content in the diet. Urea can be measured in blood, serum,
plasma or milk, with results being interpreted similarly. The current
recommendation (based on previous studies in the literature) is that the average urea concentration of
the tested cows should be between 13-17 mg/dL. Both high and low values
indicate the need for modifying the content of the ration.
- Albumin: Albumin values are also
used to reflect the nutrient and energy content of the diet. Some
investigators use a goal of > 3 g/dl for an average albumin value
of the tested animals. Note that albumin concentrations are also affected
by other conditions including inflammatory states (albumin will decrease
because it is a negative acute phase protein), liver disease (albumin
is produced in the liver), and renal and gastrointestinal disease
(albumin can be lost in these disorders).
Copyright © Cornell