The current
problems of low milk prices faced by dairy farmers mean that increasing
productivity is even more critical. Low milk prices mean that maximising the
number of litres produced and minimising the cost of production is paramount.
To do that requires ensuring that cows are in the best physical shape, allowing
them to deliver in terms of milk yield and solids.
The Gutworm
threat
Infections with
Gutworms are very much an underestimated cause of reduced performance in
pastured dairy herds. Previously it was always assumed that adult dairy cows
could easily deal with parasitic infection and that such infections would not
have any detrimental effect on productivity. Recent evidence has emerged
regarding the negative impact that gutworms can have on the productive
performance of adult dairy cows.
The effects of gutworms in
dairy cows can be divided into clinical and subclinical effects. Outward
visible symptoms-clinical signs of gutworms including scouring and rough coat
are relatively unlikely to occur in adult dairy cows. This is more common in
young stock during their first or second grazing season.
Losses in the
animal’s productivity without outward clinical signs, otherwise known as
subclinical effects are the much more common presentation in adult dairy cows.
Subclinical infections are more difficult to detect but are a major cause of
reduced productivity in dairy herds. Adult dairy cows can harbour a large
number of gastrointestinal parasites (mainly Ostertagia ostertagi).
One 1999 study
found that between 83% and 100% of culled dairy cows were infected with gut
worms. If as this study suggests, most herds are suffering from a high gut worm
burden it means Irish dairy farmers are losing money as a result.
Dairy cows are
bred to produce vast quantities of milk and are therefore under nutritional
pressure so even a few parasites can reduce production in these high yielders.
For example, the same burden of worms in a suckler cow is likely to cause
little or no production losses. Because of the demands of lactation it takes
fewer parasites in high producing dairy cows to cause economic losses than it
takes in lower producing animals that are not under the same pressures.
Gut worms can also affect the
animal’s immune system. Animals harbouring a gutworm infection will be
immunosuppressed. This can interfere with the animal’s ability to deal
effectively with infections that they are exposed to. The freshly calved,
transitional cow is already immunosuppressed and the presence of worms
magnifies this immunosuppression.
The benefits of
worming dairy cows with an Eprinomectin cased wormer:
1. Milk Yield
Numerous studies
have shown that a worming treatment of dairy cows can result in a positive milk
yield response. Studies show up to a 2l increase per cow per day. The quality
of the milk produced from treated animals is also superior, with consistently
higher milk fat, protein and overall milk solids.
2. Animals graze
longer
Treated animals
have also been shown to graze for up to an hour longer each day, which can
increase their DM intake by up to 1kg per day. Milk yield is positively
correlated to dry matter intake. High dry matter intake (DMI) results in high
nutrient intake and therefore higher milk yield, where the difference in yield
was up to 2.35kg/day between treated and nontreated, and is particularly marked
in heifers.
3.Fertility
Not only are there significant
benefits to worming treatments in terms of the production parameters, the fertility
indices of treated animals can also be significantly improved, with improved
calving to conception intervals associated with treatment at calving13, and
higher conception rates at first service (58% treated animals V 38%
nontreated).
Diagnoses
A bulk tank milk
test for the measurement of antibodies to the main gutworm -Ostertagia
ostertagi exists. This test helps to give an indication of the level of
exposure within a herd to this harmful gutworm. The results of this test
are expressed as a ratio and offer an excellent tool to assess parasitic burden
within a dairy herd. The higher the ratio the greater the potential benefit of
treatment of that herd for gutworms. Overall the Bulk Tank Milk Tests can be
used to identify those herds where the greatest milk yield response after a
worming treatment is expected and can contribute to a strategic and justified
use of an anthelmintic.
Lungworm in
Dairy Cows
Over the last
number of years the problem of coughing dairy cows has become much more
prevalent. Reinfection Hoose or lungworm can be the cause of this. When the
immunity of these adult animals is low, they can become parasitised by lungworm
larvae, resulting in the clinical signs of coughing, milk drop, weight loss and
secondary bacterial infections. If adult cows that are only partly immune to
lungworms are exposed to heavy larval challenges from pasture they may develop
severe respiratory signs.
Pasture grazed
by calves will be likely to have a heavy larval burden. In situations, where
wet weather follows a period of dry conditions this can cause a mass release of
lungworm larvae from dung pats increasing the likelihood of animals developing
lungworm.
Diagnoses
Clinical signs of lungworm
include coughing and difficulty breathing, as well as milk drop, weight loss
and death in severe cases. Famers should remain vigilant of these clinical
signs and take steps to treat appropriately.
Treatment
As soon as
lungworm is identified in a herd, it is extremely important to treat the whole
herd and to instigate treatment as quickly as possible. Delaying treatment can
result in permanent damage to the lungs, affecting the animal’s long term
performance as well as making them more susceptible to secondary infections.
Treating cows with lungworm is quite different to treating cows with an
underlying gut worm burden. Cows with lungworm are clinically sick while, those
with gutworms are more likely to be clinically well but production may be
compromised.
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