background image
42
APRIL
Dairy Focus
www.irishfarmersmonthly.com
in the grass over the second and subsequent rotations
is also important as "heavy cover" will lead to lower milk
protein in the mid-summer period due to farms forcing
cows to consume less digestible grass. The inclusion of
supplements needs to be strategic, again depending on
milk yield and grass availability, with the option to increase
it on wet days and bring in some high-quality bale silage if
this weather event extends beyond a number of days.
Milk fat percentage has also become an increasingly
important factor over the last number of seasons as
some farms begin to understand the consequences of
lower butterfat, even beyond a milk price deferential. This
is evident in the mid-summer period, especially in the
second and subsequent grazing rounds. This can even
manifest itself as a fat inversion, where it is lower than the
milk protein.
Traditionally lower butterfat would have been associated
with reduced rumen health and in extreme cases clinical
or sub-clinical signs of acidosis. This holds true even today
but further research in the interim has shown that over
50 percent of cows experience low rumen pH, which is a
measurement for rumen health, during the grazing period
and they might not show any clinical or sub-clinical signs
of acidosis other than lower butterfat readings. These low
butterfat readings can also be due to a combination of low
pH during grazing and the amount and feeding method of
rapidly fermentable concentrate supplements. Therefore,
low butterfat could be a sign of poor rumen health, but
not necessarily a sign of acidosis.
If butterfat drops during the second and third round
of grazing, then each case and each farm need to be
assessed individually.
What is grass quality like?
What level of concentrate is being fed per milking?
What is the make-up of this concentrate?
Is there supplementary forage being used?
Are there other e ects on the cow other than reduced
butterfat percentage? e.g. a fall in milk protein;
reduced milk yield; body weight loss; manure score;
increased evidence of lameness or "soft feet".
In all cases we need to bring about di erent actions and
these actions need to be more pronounced if we are
experiencing other symptoms.
We should strive for excellent grass quality and covers
of 1200-1400 kilograms of dry matter intake per hectare
will work better for milk yield and protein percentage
rather than butterfat percentage. At a basic level we
need to avoid over-feeding concentrate and make sure
the digestible fibre content is su cient, versus the sugar
and starch content. We can bring additional sources
of fibre into the diet in the form of forages or straw
as a supplementary bu er feed to avoid over-feeding
concentrates. This can be a big step for some farms and
care must be taken to avoid supplementing too much
grass with conserved forage, as we might increase our
butterfat percentage but drop our butterfat protein
through reduced yield. The use of a live yeast in the
concentrate is also a must when trying to counteract an
unstable or low rumen pH, and especially during this time
you should be making sure your concentrate supplier has
this included along with your Cal mag and minerals as a
minimum.
Of course, there has been other reasons for drop in milk
fat with cows in a grazing environment which is the
discovery of CLA or conjugated linoleic acids in grass.
The presence of linoleic acid, which is prevalent in most
forage species, and is especially abundant in lush grass.
You can end up with animals on a high fat diet and this, in
conjunction with lower fibre and digestible grass, causes a
lower rumen pH and thus can lead to the perfect storm.
Low butterfat alone generally improves in seasonal herds
as grass reaches a reproductive stage and may only persist
for 2-3 weeks with little or no consequence for herd
health in the grazing environment. Milk protein will be
determined on grass quality and how the condition of the
cow recovers later in the season. Determining overall dry
matter intake, and milk solids output is more important
than focusing on butterfat or protein alone, with milk
solids changes being more important. If there are reduced
intakes, a drop in yield or total solids, or reduced body
condition, then addressing the issue in a total context
with a well-constructed bu er makes more sense. The
overall solution is to avoid it happening in the first place
by looking after the quantity and quality of the dry matter
consumed by the animal and beat the drop in the first
place.
Glanbia 197x279.indd 1
20/03/2019 15:15