Negative Energy Balance & Trace elements testing


To give cows the best start of a new lactation it is important to control their energy balance and correct mineral and trace element deficiencies.

Negative Energy Balance (NEB)

When cows require more energy than the level supplied through the diet, they are in a state of Negative Energy Balance (NEB) and break down their body fat reserves to compensate for the shortfall. This happens to nearly every dairy cow in early lactation when she reaches peak milk yield, but can already appear at the end of the dry period when a large proportion of a cow’s energy intake is consumed by the growing calf foetus. An episode of NEB during the transition period, approximately from 3 weeks before until 3 weeks after calving, may impact a cow’s recovery from the calving event, lead to a higher risk for retained foetal membranes, milk fever, ketosis, mastitis and LDA’s as well as negatively impact fertility in the upcoming breeding season.

Fat dry cows (Body Condition Score greater than 3.5) are much more prone to develop excessive NEB after calving. High BCS suppresses feed intakes and a BCS of 3.0 – 3.25 at calving is considered optimal. Lactating cow feed should be introduced in small amounts from two weeks before calving, to allow adjustment of the cow’s digestive system. Further nutritional changes should be made gradually during the first few weeks of lactation. To ease the transition from dry to lactating, a sufficient supply of high quality forage is essential for cows in late pregnancy.

Monitoring the concentration of key metabolites in blood samples taken from cows during the transition period can help vets and nutritionists evaluate the energy status of the herd and adjust the cows’ diet before clinical disease appears. Recommendations are to test between seven and twelve ‘close-up’ cows near the end of the dry period and between seven and twelve freshly calved cows in the first three weeks of lactation, prior to feeding. At a minimum, the blood samples from the ‘close-up’ cows have to be tested for NEFA levels, which gives a good indication of energy balance prior to calving. The blood samples from the freshly calved cows have to be tested for NEFA as well as BHB. The NEFA result will offer insight into the energy balance of the milking cows whereas the BHB reading is associated with the development of ketosis as a result of excessive NEB and body fat reserve breakdown. Cows with high NEFA or BHB may have reduced dry matter intake, suppressed immunity, decreased pregnancy rates and increased risk of ketosis and LDA. If more than 15% of the cows tested have readings above the relevant thresholds for either NEFA or BHB, action has to be taken to mitigate the NEB.

Further energy balance monitoring of the milking cows can be done based on bulk tank and individual cow milk protein levels during the first 2 months of lactation as well as frequent BCS assessment of the herd. Milk and urine dipsticks are available to test individual cows for ketosis.

Assessment of trace element status

Most important is the dry period and early lactation. Blood samples for Cu, GPx, and PII testing will give a picture of Copper, Selenium and Iodine status respectively. Zinc and Calcium can also be tested on these samples.

Test 10 – 12 cows across different lactations and a cohort of young stock if they are grazed on different land or are offered different silage.

Blood samples should usually be collected in green tubes. Depending on the lab, copper testing often requires red tubes. A liver biopsy or liver tissue from cull cows would give a more accurate result for copper than a blood test.

Trace elements of concern in Ireland are copper, selenium and Iodine. When left unsupplemented, grazing Irish herds are likely to suffer from selenium and iodine deficiency.

Variation in Irish grass and silage concentrations of Cu, Se and I (mg/kg DM)

Grass Silage





Average Max
1.6 9.2 23.7 
2.8 10.4  39.7
0.01 0.09 2.5 
0.02 0.09 2.3 
0.05 0.26 1.00 
0.02 0.27 2.32 

First Published 14 January 2022

Tagged with: Dairy


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