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.
