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30
APRIL 2018
Dairy Focus
www.irishfarmersmonthly.com
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appear angular and there is little to no fat pad on palpation. To
refi ne BCS below 2.75, the focus is then placed on evaluating
the short ribs (Ferguson et al, 1994).
Figure : Anatomical areas for dairy cow body condition scoring.
BCS loss greater than 0.5 units after calving increases days to
fi rst service and reduces conception to fi rst service (Butler and
Smith, 1989). According to the Irish Cattle Breeding Federation
(ICBF), Ireland's national six-week calving rate is 58 per cent,
and this is far behind the commercial target of 90 per cent. The
disparity in calving compactness between the target and the
actual calving rate is costing 8.22 per cow that is per 1 per cent
below 90 per cent (McCarthy et al, 2017).
Implementing regular BCS on your farm leading up to breeding
will highlight the high-risk cows that require attention. This
high-risk group would include underconditioned high yielders,
heifers, lame cows, diffi cult calvers and non-cycling cows.
Could the underconditioned high yielders or heifers be topped
up extra in the parlour? Could the lame cows be kept in or close
to the parlour to ensure optimum DMI with no competition?
Are the cows' DMI restricted at grass? Does the overall energy
in the buff er and the parlour need to be increased? BCS will
highlight the strategy that needs to be taken to have a successful
subsequent breeding.
BUFFERING AT GRASS
There is no denying that getting cows out to graze this year
was delayed because of wet weather, ground conditions and
insuffi cient grass growth. Similarly, farmers moving into their
second rotation are reporting that cows will be going into low
grass covers of 650-1,000kg per hectare. This scenario indicates
an approaching energy and DMI defi cit for the mid-lactation
cow. A buff er to complement high-protein, fresh grass must be
high in starch, digestible fi bre and be highly palatable. Buff er
feeding is designed to fi ll shortfalls in grass supply and quality.
While the objective is to work with the feeds that are available
on-farm, ideal feeds to use for buff er feeding include high dry
matter digestibility (DMD) silage bales, maize silage, whole-
crop cereals, fodder beet, molasses, cereals, beet pulp, maize
meal and straw. After spring, the availability of alternative
forages is not an option. Buff er feeding is limited to grass silage,
moist feeds, molasses and forage-extending concentrates. At
this time, it is worthwhile to plan for next spring and consider
securing tonnage of maize/whole-crop to be grown by a
contractor.
VITAMINS AND CAL MAG
As the mid-lactation cow increases her DMI from grass and
receives less from supplementary feeding, it is important to
ensure that the correct levels of minerals and Cal-Mag are still
in the diet. Ideally, the feeding rate of the parlour concentrates
should have the correct pro-rata levels of mineral. As the
level of concentrates decrease in the parlour, it is worthwhile
to manually weigh what is in a `pull' in the parlour to ensure
correct calibration. To avoid grass tetany at grass, a feeding
rate of 1.1kg in the parlour requires 5 per cent Cal-Mag, a 2.25kg
feeding rate requires 2.5 per cent Cal-Mag inclusion and 4.5kg
requires 1.25 per cent Cal-Mag per tonne.
The integral role that minerals play in the resumption of
cyclicity and successful breeding of the mid-lactation cow
cannot be overlooked. Going into breeding, we want a cow
that has a healthy immune system and displays a strong
heat. Defi ciencies in certain trace minerals can be related to
infertility. For example, anoestrous behaviour and silent heats
in the herd are linked to defi ciencies in copper and manganese.
Optimum levels of organic selenium have reduced incidences
of metritis and reduced services per conception signifi cantly
(Agovino, 2011). It is important to have a proportion of the
mineral supplied in an organic form. The mineral is then
more bioavailable for absorption by the cow and there are less
interactions with antagonists.
SUMMARY
As the cow enters into mid-lactation (100-200 days in
milk), her appetite has fully recovered post-calving and peak
milk yield has been attained. In order to maintain a steady
lactation and a successful breeding, it is vital that there are
no restrictions in DMI. At regular intervals, it is key to review
changes in milk protein, milk yield and BCS, and consider
whether there is an energy defi cit or a requirement for
supplementation at grass.
References available on request