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MAY 2019
Mid-season nutrition and the
management of the dairy cow
Cathal Cassidy, InTouch Feeding Specialist, Alltech Ireland, examines the management of the cow's
diet for a successful breeding season
As many dairy farms move on to their second rotation
of grazing, and as breeding kicks off for spring calving
herds, we producers must consider how we are managing
our cows' diet and nutrition in order to have a successful
breeding season and to maintain milk production. Our
main focus now should be on managing grazing and
providing a suitable supplementation for grass, which
will have a direct effect on cow performance and the
maintenance of milk solids. This is also an ideal time to
assess and manage feed stocks and make plans for the
year ahead.
Meeting the cow's requirements
When it comes to cow nutrition, the number-one focus
is always to meet the cow's total dry matter intake
(DMI). To determine DMI, divide your cow's milk yield
by 1.5, which is their ideal feed efficiency (FE) this time
of year. Feed efficiency is the number of kilograms (kg)
of milk produced per kilogram DMI; for example, a cow
yielding 27 litres will require around 18 kg DM/day. Next,
determine how much of this she gets from grass and
supplement accordingly, usually through concentrate
feed. It is also important to know what the top cows
in the herd are yielding. If the herd average is 27 litres,
for instance, then the top 20 percent of cows could be
yielding 35 litres or more, which means they have different
DMI requirements (around 23 kg DM/day).
Generally, in ideal conditions, cows will be able to graze
a maximum of 16­17 kg DM of grass/day. Farmers should
be attempting to maximise grass intake, as grass is both
the cheapest and the highest-quality feed available. What
happens on many farms during this part of the grazing
season, however, is that intakes from grass are either
overestimated or limited. As a result, cows are underfed,
leading to a drop in milk yield, fat and protein.
Limiting factors
When it comes to grass intake, one limitation many farms
face is paddock size; herds have grown, but cows are still
being allocated the same grazing area, meaning they run
out of grass before they can reach their maximum grass
intake. Something as simple as matching paddock size
and grass allocation with herd size will help increase the
production of milk solids. Average grass intakes can be
determined by knowing the pre-grazing cover and area in
a paddock, allowing cows to be adequately supplemented
to meet their total DMI.
Calculating grass intakes
Pre-grazing cover ­ 50 kg × Ha in paddock ÷ cow numbers
= grass intakes
Wet weather can also limit grass intake, as it decreases
grass dry matter and, in turn, grass utilization, making
it physically difficult for cows to eat enough grass to
meet their DMI. As such, producers should increase
supplementation during times of heavy rainfall. As a rule
of thumb, on wet days, increase feed in the parlour by
1­2 kg; if the wet weather persists, a small buffer feed
of quality silage should be introduced. Alternatively, if
grazing conditions are suitable, push grass intakes by
reducing supplementation -- but any changes to the
cow's diet should be implemented slowly.
Grass quality
As is most evident this time of year, grass quality also
has a major impact on milk solids. Lush second-rotation
grass causes a drop in milk fat, due to its high sugar and
oil content and low amounts of fibre. When attempting to
increase the fibre content of the diet, aim to graze covers
above 1,300 kg DM/Ha. Additionally, to support milk fat
percentage, make sure to include a live yeast product --
such as YEA-SACC® from Alltech -- in your concentrate
Heavy grass covers will also affect milk quality, as their
reduced feed value will result in decreased milk protein
and yield. They can also be difficult to graze out properly,
which has the added effect of reducing grass quality in the
Beef Focus