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SUMMER FEED ING
9
LIVESTOCK MATTERS
WORKING
TOGETHER
FOR A HEALTHIER FUTURE...
Veterinary Surgeon
Matthew Pugh
XLVets Practice
Belmont Veterinary
Centre
The limitations of
summer grass
There are huge differences between seasons,
but in general, the amount of milk produced
from grazed grass declines significantly from
June onwards.
The energy content of grass stays relatively
constant at around 11.5 MJ/kg DM. However,
its Dry Matter (DM) content is hugely variable,
as it is dependent on weather conditions
throughout the grazing season. With
decreasing daylight, colder evenings and
poorer weather, DM content declines.
Grazing management will also affect quality.
Dry matter intake is dictated by grass
availability and its dry matter content and the
amount of grazing time available. Together
these factors drive milk production from grass
from mid-summer onwards.
As the end of the grazing season approaches,
not only does the DM content of grass
decrease, but also grass growth declines,
as does its digestibility.
So it is not unusual to find all-year round
calving herds where declining grass quality
and quantity has reduced the potential for
energy intake. This results in a negative energy
balance and the loss of body condition in
cows either late in lactation and/or in early
lactation. This then leads to poor fertility in
summer calving cows, and extended
calving intervals.
Typically, these cows are high yielders and
struggle to physically eat enough grass to
meet their total energy requirements. In
addition, the high protein content of grass
drives milk production and to meet the energy
gap, the cows mobilise fat i.e. milk off their
backs, leading to a drop in body condition
and significantly impacting on their
subsequent fertility.
Monitor body condition
The key to managing cows at grass is to
monitor their body condition - this serves as
an early warning system when dietary energy
and protein levels are lacking.
In addition to regular body condition scoring,
metabolic screening or blood profiling can be
undertaken by your local XLVets vet to assess
the energy status of a group of cows.
When cows fail to meet their energy
requirements, they mobilise fat to compensate.
This is broken down in their livers into ketones
and then used as an alternative energy source.
So by measuring ketone levels we can
determine the extent of the dietary energy
deficit, and take appropriate action from there.
Cows typically targeted at routine visits are
cows which have calved 7-14 days previously
- this determines how successful the dry cow
management is. Also tested are cows which
are at 40-50 days into their lactation - this
assesses how well the current milking cow diet
is meeting the energy requirements of high
yielding cows.
Cheap on-farm testing kits such as ketone
meters (below) are available which can
be used by your vet at routine visits on a
percentage of the cows that are at highest
risk of ketosis. These give instant readings
on blood ketone status and provide an
indication of herd energy status.
Advice on late
summer feeding
for
dairy herds
MATTHEW PUGH,
BELMONT VETERINARY CENTRE
Through mid-summer and autumn, there can be an over-reliance on
grazing which leads to a shortfall in nutrient supply to cows, reducing
their energy status and impacting on milk yields and fertility. So it's
important to monitor your herd's body condition scores and take action
to ensure a sufficient supply of nutrients, and adapt buffer feeding
policy if needed.