Coccidiosis: The Stealth Bomber to Dairy Operations
Most dairy producers recognize the clinical signs of acute coccidiosis
— bloody diarrhea, long strands of intestinal lining in watery,
mucus-filled stools, straining to defecate without stool.
From experience they also know that, if left unchecked, coccidiosis can
lead to mortality rates of 2 to 5 percent. Those that do survive become
“poor doers” and take significantly longer to mature, breed and reach
the milking line.
Common sense and good animal husbandry practices go a long way toward promoting good animal health. The first weeks of a calf's life are critical. With a life cycle of 3 to 4 weeks, coccidia can begin the infective process soon after calving, with coccidiosis outbreaks occurring as soon as soon as 4 weeks after birth.
Because coccidiosis outbreaks in young calves result in mortality rates of up to 5 percent or higher, it's important to handle these calves well from Day One, says Dr. Bert Stromberg, of the University of Minnesota.
Follow this checklist to ensure optimum health and performance:
- Ensure adequate colostrum intake within the first hours of life.
- Tidy up - keep calf hutches, pens, and pastures clean and dry.
- Isolate sick calves to prevent disease spread.
- Clean and disinfect boots and wash hands after handling sick calves.
- Follow strict sanitation practices when moving between cows and calves.
- Keep feed off the ground to prevent ingestion of coccidia.
- Use an approved anticoccidial, beginning in the milk replacer.
- Continue the anticoccidial in the starter and grower feeds to avoid lapses in coverage.
Fortunately or unfortunately for dairy
operations — depending on how one looks at it — acute coccidiosis and
its telltale signs appear in only 5 percent of calves. But that doesn’t
mean the rest of the herd isn’t infected or losing money.
Subclinical, or chronic, coccidiosis can be even more costly because it
usually goes undetected. Infected cattle appear “healthy” as this
stealthy intruder quietly slips into cattle and robs producers of gain
and performance dollars — without leaving any obvious damage behind.
Know your enemy
To understand how coccidiosis works, one needs to understand what
causes the disease and how it manages to evade radar on most dairy
operations.
Coccidiosis is caused by highly prolific
microscopic protozoa parasites. Two species, Eimeria bovis and Eimeria
zuernii, are responsible for the majority of clinical coccidiosis in
cattle and are found virtually anywhere dairy herds are present. The
disease is transmitted from one animal to a n o t h e r through an
infecting egg, or oocyst, found in feces, soil, pastures and stalls.
Because cows are carriers and readily shed the organism, new calves
come in contact with oocysts as soon as they hit the ground. And after
that, they’re exposed to millions more.
According to
published reports, for every one oocyst ingested by a calf, 15 to 28
million — none visible to the naked eye — can be returned to the
pasture or stall at the end of the oocyst’s life cycle in 3 to 4 weeks.
Ingesting only 50,000 oocysts, or 0.1 percent, of the estimated 50
million a cow passes each summer in her manure can cause severe
intestinal disease.
Acute coccidiosis
To avoid bouts with coccidiosis, calves need to consume at least 4
quarts of colostrum within the first 12 hours of life to boost their
immune system. A clean, dry environment is crucial as well — a tall
order for any livestock operation.
“In the first month of life, calves without adequate colostrum intake
are susceptible to death from acute coccidiosis,” says Dr. Bert
Stromberg, professor of veterinary science at the University of
Minnesota College of Veterinary Medicine. Once clinical signs of
coccidiosis are present, the disease is more than halfway through its
life cycle, making treatment difficult. “Unfortunately, by the time we
see the clinical signs of acute coccidiosis, many calves have already
experienced extensive intestinal damage,” points out Stromberg. Rather
than waiting for coccidiosis to strike, many experts recommend
preventive treatments for all animals. “Prevention through the feeding
of anticoccidials — beginning with milk replacers and starter feeds —
is much more effective than treating coccidiosis outbreaks,” explains
Stromberg.
Once the calf ’s gut lining is damaged by
coccidiosis, it has difficulty repairing the tissues to the level of
original absorptive action — even after disease symptoms are gone.
According to Stromberg, the loss of significant functional gut to
coccidiosis makes it hard for the calf to get back on track. “A calf
that survives an outbreak may never realize its gain and growth
potential,” he adds.
Subclinical coccidiosis
The
elusive subclinical infections of coccidiosis require more vigilance to
avoid significant losses. Because this form generally goes undetected,
diagnosticians have had difficulty gathering significant data showing
its prevalence, even though they know coccidiosis is definitely out
there. According to a 1998 report in Dairy Herd Management, the real
losses from coccidiosis occur in the 95 to 98 percent of coccidiosis
infections that go undetected.
“Calves with subclinical
coccidiosis really don’t give you any specific clues or symptoms to
pick up on,” observes Stromberg. “Unless a routine fecal exam turns up
thousands of oocysts, no one suspects the presence of coccidiosis.”
Today, the best-managed dairy herds recognize coccidiosis as a
continuous potential threat, says Stromberg. “Progressive dairies are
aware of coccidiosis and use approved anticoccidial, starting in the
milk replacer, to stay ahead of the game and protect the health and
digestive system of the dairy calf,” he adds.
Dr. Lance Fox, a technical service veterinarian at Alpharma Animal
Health who works closely with the disease, also agrees that prevention
is the best strategy because it makes cattle less susceptible to
respiratory problems. “By preventing coccidiosis early in the game,
beginning with the milk replacer, you eliminate the suppressive effect
that coccidian have on the immune system. That in turn allows the
immune system to respond better and effectively to secondary infections
and respiratory disease, thereby keeping calves healthier,” he says.
Because calves are most susceptible to coccidiosis from birth to 6
months, Fox says it’s critical to start using an anticoccidial in the
milk replacer and continue with approved treatments in the starter feed
so animals can stay healthy and grow efficiently.
Preventing an outbreak
According to Stromberg, well-managed dairies also rely on sanitation to
help keep the oocyst levels down. Clean, dry calf hutches, deep dry
bedding, manure removal and employee sanitation all play an important
role in reducing oocyst transmission. He cautions, however, that
sanitation and preventive measures can be undermined by stress on the
calf. “Animals under stress often reduce their feed consumption,
opening the door for infection,” he says. “Multiple stressors combined
with a large enough dose of coccidia can overwhelm a calf ’s immune
system, making an infection imminent.”
Heat stress, cold
stress, change in feed, moving, processing, castration are all stress
factors that can weaken a calf ’s immune system. “Some stressors you
have no control over,” Fox adds, “so an anticoccidial is needed to
prevent outbreaks and to stop losses from hidden infection.”
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Alpharma, Inc.
