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Fertility issues
Kirsty decided further investigations were
needed, and that Neil needed to sacrifice
two of them which were not in-calf, for
more post-mortems. She suspected copper
toxicity amongst other possible causes,
and specifically requested liver analyses.
Her hunch was right – copper levels in the
livers were ‘sky-high’. A further six animals –
of different ages and stages of lactation –
were also sent for slaughter as cull cows,
and Kirsty requested that liver samples be
taken. Again, levels were high, and
especially so in two old late lactation cows.
Neil adds: ‘Over a 7-month period, we lost
15 cows. Looking back over time, we had
lost a similar number over previous years. It
was always the older late lactation cows that
died. Fortunately we had sufficient home-bred
heifer replacements coming through to main-
tain herd number and output.’
Copper toxicity
Kirsty explains: ‘Cattle can cope for long
periods on high copper diets. There is no
excretion route for copper other than in milk
production, so any excess is stored in the
liver. Over time this will reduce liver function.
Outward signs of toxic build-up include
reduced milk yield, inappetance, lethargy,
weakness. Immunity is also compromised.
‘When the liver reaches a critical point of
overload, it releases large quantities of
copper into the bloodstream, effectively
rupturing the red blood cells. Death is
instantaneous.
‘Early signs of copper toxicity are rather
vague, and diagnosis is not simple. Copper
toxicity won’t show up in milk or blood tests.
It’s necessary to either sacrifice a live animal
for liver autopsy or have a biopsy carried out
– neither of which are cheap.’
Removing dietary copper
Having identified copper toxicity, Kirsty and
the Sowerbys consulted with the nutritionist,
and from August, all sources of copper were
removed from both the milking cow and dry
cow rations.
Kirsty explains: ‘Although this meant no more
copper could get into the livers, they were still
full of copper, so we needed to get it
mobilised and into the milk. The nutritionist
organised a custom-made high molybdenum
premix for all the diets. This would bind up
all remaining copper in the diets, and draw
the stored copper out of their livers.
‘In a matter of months, we started to see
improvements in cow fertility, as a result of
the dietary changes.’
Care with copper
Kirsty adds: ‘It is vital when calculating
copper intakes that every source is
considered. A nutritionist will be aware
of the copper going in via the concentrates
and straights within the main ration, but may
not be aware of the levels in mineral
premixes as these are often purchased
from different sources. This was the root of
the problem at Townhead Farm – a mineral
premix with far too high an inclusion of
copper.
‘Similar toxicity issues can also occur when
farmers are using boluses for their dry cows
with selenium and iodine to prevent weak
calves. These boluses also provide ample
copper for 4-6 months, so the farm’s
nutritionist needs to know about this!
‘Another common error made is to add ‘just a
bit more’ premix than prescribed, thinking that
increasing mineral levels will have a positive
effect. This is not necessarily the case, and it
will cost more for no gain.’
SPRING 2016 ISSUE
LIVESTOCK MATTERS
6
COPPER TOX I C I TY
TMR – a high copper mineral premix in the TMR
was tipping cows into toxicity
Kirsty explains: ‘Copper has a narrow
therapeutic/feed window; this means
the difference between animals being fed
a deficient diet and a toxic diet is small.
So it is important to be aware of the levels
being fed. Nor should feed levels of
copper be viewed in isolation, because
there are so many complex interactions
with other minerals and trace elements.
‘The maximum legal limit for feeding
copper is 40mg/kg DM fed. But this is
a maximum – not a target level!
‘For most dairy cattle 7-12mg/kg DM
is ample to sustain good production and
fertility. The exception is in areas where
other elements may limit absorption, e.g.
the Somerset ‘teart pastures’ where
molybdenum levels are exceedingly high
and bind the copper.
‘There are breed differences too. Holsteins
don’t require as much copper as Friesians,
and Jerseys need even less.’
Copper: How much to feed?
Copper toxicity was manifesting in later lactation
cows giving less milk
At Townhead Farm, Neil is now sourcing his
mineral premix through his nutritionist, and a
low copper cake is now fed in the parlour.
There have been no more cattle deaths since
October. Fertility has been steadily improving
too with improvements in heat expression and
conception rate. The submission rate is now
55% and pregnancy rate 20% – a good
level for a Holstein herd.
Kirsty adds: ‘Adding less copper to the diet
has not only saved money in mineral costs,
but fertility has improved and the number of
fertility treatments required has more than
halved.
‘However, we need to be careful not to
cause a reverse problem! Blood tests can be
used as an indicator for low copper levels
and so we are monitoring heifers to ensure
their fertility will not be compromised through
copper deficiency.’
Neil and Evonne are happy to admit that
Kirsty had a challenge on her hands to
convince them to cut back on copper. ‘I was
a firm non-believer to start with!’ says Neil.
‘But I now realise I had been killing my cows
with kindness!’
Going forward
Check the specification of mineral premixes