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Nutrition: preventing disease and monitoring status in the transition cow

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01 February 2014, at 12:00am

Debbie Doyle reports on the third webinar on cattle nutrition when Dr Finbar Mulligan from the Dublin veterinary school reviewed the key parameters to use when assessing nutritional status

IN the final of three free CPD webinars organised by Elanco Animal health, independent cattle nutrition expert Dr Finbar Mulligan, from the veterinary school in Dublin, gave an in-depth and pragmatic talk looking at the key parameters that vets can use to assess nutritional status in dairy cows, and the various tools available to do so.

He listed the key parameters to monitor as:

  • benchmarking transitional health outcomes n body condition score (BCS) records;
  • calcium status peri-partum;
  • energy balance pre-calving;
  • early lactation energy balance/metabolic status;
  • rumen health;
  • trace element status.

Target incidence rates for clinical production diseases 

Dr Mulligan highlighted the fact that in well run herds the incidence of problems in the transition period are 5% or less (Table 1).

Body condition score (BCS)

At UCD the cattle health group uses a five point scale for calculating BCS and aims for the target scores at different points of the lactation cycle shown, particularly a score of 3.0-3.25 in 90% of cows at calving.

Vets should be looking at the percentage of cows reaching target BCS at each time point in the cow’s lactation as a means of assessing the herd’s nutritional status.

Calcium status

UCD undertakes screening for subclinical hypocalcaemia at 12-24 hours post-calving. The strategy used is to check blood levels of calcium are above 2.0mmol/l at this time point.

Magnesium levels are also critical for calcium metabolism, so these are also assessed close to calving. Blood levels of magnesium 24- 48 hours pre- calving should be in the range 0.8-1.3mmol/l. Potassium levels are also of key importance and potassium levels in the diet should be measured with a target of <1.8% dry matter.

Monitoring calcium status also requires BCS monitoring, forage analysis of the major minerals (especially potassium) and the calculation of magnesium supplementation that is being fed.

Energy balance pre-calving

The UCD group screens for negative energy balance (NEB) using blood metabolite analysis.

Blood samples are taken from 12 cows, 2-14 days before calving. If >10% of cows have NEFA (non-esterified fatty acids) levels above 0.4mmol/l and/or blood beta-hydroxybutyrate (BHB) levels exceed 0.6mmol/l, then a problem with NEB is suspected pre- calving.

Energy balance in early lactation 

A good starting point for monitoring energy balance in early lactation is asking the nutritionist to supply the figures for the calculated energy balance. However, BCS loss is actually the most robust assessment tool of energy balance in early lactation. BCS losses should be maintained at a minimum.

Milk composition records can be used as an indicator of NEB. Lower milk protein percentages are loosely associated with a NEB. If 15% or more of cows, between 1-100 days post- calving, have a milk protein composition of less than 3.05%, then suspect an excessive NEB.

Milk protein figures are far more useful when used in conjunction with milk fat to protein ratios. High ratios in early lactation are an indicator of a NEB. From individual cow milk records, look to see if over 10% of early lactation cows have ratios exceeding 1.5; if they do, again it is suspicious of excessive NEB.

UCD measures both blood metabolites NEFA and BHB in early lactation to monitor energy balance. Ideally, 12 cows should be sampled between 21 and 50 days post-calving.

If two cows have BHB levels above 1.4mmol/l or two cows have NEFA levels over 0.7mmol/l, then this is considered a positive result for a NEB problem. In practice, cow-side tests for blood and milk levels are available for monitoring these metabolites.

Feed factors will also influence energy balance and so silage and forage intake, their quality and analysis is crucial for a full assessment. For grazing herds, grass allowance, climatic conditions and grass growth also need taking into account.

Environmental factors can also impact energy balance and during a farm visit, feeding and drinking space, duration and space for access to fresh food and water, etc., ought to be checked. Any water restriction will limit dry matter intake.

Rumen health

Rumen health can be monitored to look for subacute rumen acidosis (SARA). Milk composition, can again be used as an indicator, although this data should be from cows that have been calved for 56 days.

If milk fat is less than or equal to 2.5% for over 10% of the herd, or milk fat percentage is less than milk protein percentage by 0.4% for individual cows, then SARA should be suspected.

Other strategies the speaker uses to monitor rumen health are assessment of faecal consistency, rumination behaviour of herds indoors and rumenocentesis.

Trace elements

Trace element intake can be calculated from the ration, forage and amounts fed. If there is a problem with fertility after healthy calvings, then blood sample cows calved for two months for more detailed information. If there are problems around calving, then sample dry cows.