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A.Sistem Sirkulasi pada HewanSistem sirkulasi pada hewan dibedakan menjadi 3, yaitu :

Sistem difusi: terjadi pada avertebrata rendah seperti paramecium, amoebamaupun hydrabelum

mempunyai sistem sirkulasi berupa jantung dengan salurannya yang merupakan jalan untuk

peredaran makanan. Makanan umumnya beredar keseluruh tubuh karena adanya aliran

protoplasma.

Sistem peredaran darah terbuka: jika dalam peredaran-nya darah tidak selalu berada di dalam

pembuluh.

Misal : Arthropoda

Sistem peredaran darah tertutup: jika dalam peredaran-nya darah selalu berada di dalam pembuluh.

Misal :Annelida, Mollusca, Vertebrata.

Mamalia

Jantung mamlia terbagi menjadi 4 ruang, yaitu :

- 2 atrium : 1 atrium dekster (serambi kanan)

1 atrium sinister (serambi kiri)

- 2 ventrikel : 1 ventrikel dekster (bilik kanan)

1 ventrikel sinister (bilik kiri)

Sekat di antara ventrikel kiri dan ventrikel kanan sempurna sehingga tidak terjadi percampuran darah

yang kaya O2dan yang miskin O2

pada ternak besar/ruminansia, meningkatnya tekanan pada artei paru-paru dapat menyebabkan

penyakit brisket yaitu pembesaran dan pembekakan pada daerah brisket yang bisa berakibat kematian.

Brisket Disease in Beef Cattle

Research

High altitude disease (Brisket Disease), which causes cattlemen at high altitudesserious problems through cattle losses, has been thoroughly studied.Pulmonary arterial pressure (PAP) measures have been shown to be a very goodindicator of susceptibility to brisket disease, and differences in PAP values have beenshown to be highly heritable.Cattlemen at high altitudes can use bulls with low PAP values to eliminate thisproblem from their herd. All bulls sold at the SJBRC are measured for PAP values.

BRISKET DISEASE - PULMONARY HYPERTENSION FACT SHEET

Brisket Disease, also known as High Mountain Disease or PulmonaryHypertension, is one of the Rocky Mountain region's most costly diseases. The

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disease is the result of elevated pulmonary arterial pressures or pulmonaryhypertension and generally affects animals less than one year of age residingat an elevation above 5000 feet.

Brisket Disease is caused primarily by an oxygen shortage; oxygen availabilityis 17% less at 5,000 feet than it is at sea level; 20% less at 6,000 feet, 26% less at8,000 feet, and 31% less at 10,000 feet. The oxygen shortage at high elevationscauses increased resistance to blood flow in small arteries in the lungs. Theheart compensates for higher resistance by stretching and building up ahigher pressure. The pressure can continue to build up until fluids leak out ofthe blood stream and collect in the chest cavity, the brisket, and other places.Eventually, the heart wears out and stops beating.

The losses from the disease can vary depending on the origin of the cattle. In

cattle born and raised at high elevations, the losses tend to run from .5% to5%. In imported or lowland cattle the losses can range from 30% to 40%.

Cattle differ in how they respond to oxygen shortage. Some cattle are able totolerate high pressures for a longer period of time, while others die quickly.Brisket disease is not limited to one sex or breed. It affects both sexes and hasbeen found across all breeds including crossbreds.

Research has shown that the heritability of Brisket Disease can be quite high,

ranging from 42% to 77%. This indicates that cattlemen can successfully selectagainst the disease by curing cattle with high pulmonary arterial pressures.

Pulmonary arterial pressures (PAP) are obtained by a procedure called "rightheart catherization". In this procedure, a fine plastic tube is passed through aneedle in the jugular vein, with blood flow into the upper right side of theheart (atrium), through a valve, into the lower right side (ventricle), through avalve, and into the pulmonary artery just short of the branches to the lungs.Pressure waves are observed on a heart monitor and the monitor gives a

direct readout of the true average pressure.

The PAP test is the best indicator (tool) available to date for identifyinganimals predisposed to Brisket Disease. The test is not 100% and should notbe used as such. Generally, cattle with PAP values greater than 50 areconsidered to be of higher risk and cattlemen should be cautious of usingthem at high elevations.

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In efforts to cut losses to Brisket Disease, cattlemen should identify thoseanimals, specifically bulls, with high pulmonary arterial pressures and cullthem from the herd or if possible, move them to lower elevations. Many timescattle with high PAP measurements or even beginning to contract Brisket

disease can be successfully relocated at lower elevations.Brisket disease in cattle is regarded as a high-elevation disease, but symptoms are being

seen in feedlot cattle at 3,000 ft.

Tim Holt, Colorado State University DVM and assistant professor of veterinary medicine

and biomedical science, has studied brisket disease in cattle for more than 30 years. His

work looking for answers to what starts as a respiratory condition in some cattle at higher

elevations and often ends in death is taking on more importance as its incidence seems to

be growing.

Is what we consider high elevation now becoming 3,000 ft., where we used to say it was

7,000 ft.? Today, were seeing brisket disease even in some Nebraska feedlots, Holt says.

Is thisrelated to genetics, disease or nutrition?

Symptons of Brisket Disease

Cattle above 6,000 ft. are most at risk of brisket disease also known as mountain sickness,

pulmonary hypertension and dropsy and incidence increases with increasing elevation. In

Wyoming and Colorado, for instance, many cattle go to summer pasture at elevations above9,000 ft.

The reduced amount of available oxygen at higher elevations can adversely affect the lungs

and cause artery walls to thicken. The decrease in the arteriesinternal diameter, and

subsequent pulmonary hypertension, make it difficult for the right side of the animals heart

to pump blood into the lungs.

Thus, the hearts right ventricle muscle enlarges from the extra effort needed to pump

blood, eventually losing tone and its ability to contract. As blood pressure increases and

starts to back up into the heart, it can blow out the valves of the right ventricle.

Some affected animals develop edema in the neck and brisket. Swelling may spread to the

jaws, or along the belly. Often, you dont see symptoms; you just find the animal dead.

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Affected animals may develop problems early in life, or shortly after being brought to high

elevation from lower altitudes, Holt says. Cattle with brisket disease are often lethargic,

while other signs may include weakness, diarrhea, bulging eyes and difficult breathing. If

cattle are trailed very far, those with brisket disease lag or lie down due to shortness of

breath.

Feedlot incidence

Interestingly, the problem sometimes appears in feedlot cattle, even at low elevations, as

they get heavier and closer to finish weight, because the heart must work harder.

It may be a different mechanism, but its the same type of issue; they are dying of right-

heart disease. Were doing research now in feedlot cattle at 3,000 ft. elevation, because

these cattle have the same clinical appearance, Holt says.

Holt has tested cattle at elevations from sea level to 15,000 ft. (in Ethiopia) utilizing a test

developed to measure pulmonary artery pressure (PAP) in humans. The PAP test helps

determine which animals are most at risk for brisket disease and detects the early stages of

the disease. The results, however, are only valid if cattle are tested at or above 6,500 ft. (see

Testing pulmonary arterialpressure in cattle).

Holt says some people think European breeds, which originated in mountainous country,

are less prone to brisket disease than British breeds, which originated at lower elevations.

But theres little evidence to support this. Holt addsthough that some cattle appear less

susceptible than others, if theyve lived at high altitudes for many generations.

When I went to Ethiopia, cattle grazing at 10,000-14,000 ft. had low PAP scores, he says.

He speculates that all the susceptible cattle had died off.

In North America, by contrast, Holt says, trait selection has concentrated on meat quality,

feed efficiency, fertility, etc. Since brisket disease on this continent is limited to small

geographic areas, little attention has been paid to how cattle function at high altitudes.

Most cattle live at lower elevations, so theres no natural selection to eliminate the

problem, he adds.

There are, however, some family lines within breeds that are more resistant than others,

Holt says. Identifying these animals can aid ranchers at high elevations in selecting resistant

animals for breeding stock.

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Rich McCormick, a Univer-sity of Wyoming (UW) professor of muscle biology, says selective

breeding of cattle in the Rocky Mountain West has reduced incidence of brisket disease to

about 5%. But this still has a significant impact on profitability, he adds.

Seemingly normal cattle may have high PAP scores at high elevations, McCormick says.But, once an animal comes to our area 7,200-8,000 ft. elevation Im not sure youll find

a truly normal individual. Of the animals weve PAP-tested at UW, weve never found one

that tested below 40, (see PAP testing).

Looking for markers

At UW, McCormick and Mark Stayton, professor and chair of UWs Molecular Biology

Department, are exploring the molecular biology of brisket disease, looking for better and

cheaper diagnostic markers to identify early stages of the disease. Were trying to develop a

blood-based diagnostic test based on gene expression, he explains.

Some animals are more susceptible, but we can currently only detect this after we bring

them to higher elevation. If they are raised at low elevation, you might never know if they

(or their offspring) would develop brisket disease.

This is what limits the use of genetically superior sires at high elevations sires that are

superior in meat production and other desired traits. Sires untested for brisket disease may

produce progeny that might develop brisket disease, McCormick says.

McCormick says human patients have been identified with an inherited form of pulmonary

hypertension, which shows similar symptoms to brisket disease in cattle. In humans,

mutations in bone morphogenic protein receptor 2 (BMPR2) have been shown to be

necessary for development of familial pulmonary hypertension, he explains.

We set out to test the hypothesis that the BMPR2 signaling pathway is defective in cattle

suffering from brisket disease and started looking at the gene in cattle. We havent yet

identified any mutations in the bovine BMPR2 amino acid sequence that correlate with

elevated PAP score, but weve found evidence that BMPR2 expression in cattle is reduced inlungs of animals with elevated PAP scores and brisket disease, he says.

McCormick and Stayton are currently cloning BMPR2 from related ruminants that are

altitude-resistant. Well compare these sequences in an effort to identify genetic changes

that correlate with altitude sensitivity. Weve obtained blood samples from alpaca, elk, yak,

and bighorn and domestic sheep, as well as cattle. Except for cattle, all these species are

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altitude-resistant. Any findings that link particular DNA sequences to disease susceptibility

are potential diagnostic markers for brisket disease, McCormick says.

Of all mammals tested, cattle are the most susceptible to pulmonary hypertension, and if

stressed, they become more susceptible. The only bovine Im aware of that seems truly

resistant is the yak. They do fine at 18,000 ft. or higher, he says.

McCormick says that if the genetic basis to brisket disease can be determined, and a genetic

marker highly correlated with development of brisket disease found, producers would have

a way to evaluate an animal without bringing it to the high country for testing. We have

ideas for future research, but except for a few cattle producers in the West, no one is

interested in funding this type of research, McCormick says.

The bovine genome is available, but we dont know if it represents cattle that are free ofgenetic components responsible for brisket disease. Did it come from an animal that was

resistant or susceptible? We dont have a good baseline to compare brisket disease-

susceptible animals to, he says.

Other ongoing research is looking at the effect of nutrition in various areas across the

country and at various altitudes to determine its effects on elevated PAP measurement.

Some studies are looking at diet, to see if certain additives, carbohydrates or protein loads

affect the pulmonary vascular system.

Were also looking at whether elevated PAP pressure can be related to fat (body condition).

Cattle nearing finish weight, with more body mass, seem more at risk. We want to find out if

the extra body mass is causing the hypoxia (shortage of oxygen) in tissues, Holt says.

Sidebar: Testing pulmonary arterial pressure in cattle

The pulmonary arterial pressure (PAP) test measures blood pressure in the pulmonary

artery and estimates the force required to push blood into the lungs. The higher the altitude,

the more accurate the test.

Cattle tested at low elevations may have acceptably low scores, but test higher at higher

elevations. The test must be done at elevations above 6,500 ft., and cattle must have been at

that elevation for at least 3-6 weeks, says Tim Holt, Colorado State University DVM.

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PAP test reliability is also better if the animal is at least one year old. Calves can be tested,

but low scores dont mean they wont develop brisket disease later. The body is still growing

and lung capacity hasnt reached its limit, Holt adds.

To test an animal, a catheter is inserted into the jugular vein, threaded into the rightventricle of the heart and into the main pulmonary artery between the heart and lungs.

Pressure in this artery is measured to determine blood pressure in the hearts right side. The

higher the blood pressure, the less capable the animal will be of living at that elevation.

In cattle older than 12 months and tested at or above 6,500 ft., a PAP score of 30-35 is

considered excellent. Any score less than 41 is acceptable, but Holt says yearlings should

measure less than that (depending on the altitude of the test).

Any animal with a score of 41 or higher should be retested prior to breeding. A PAP score of

41-45 is acceptable for animals more than 16 months old, while a score of 45-48 is

acceptable only for older animals that have been at high elevation for a long time. Animals

in this range are susceptible to environmental stresses leading to brisket disease and should

be considered at risk. Animals scoring greater than 49 must always be considered high-risk

for brisket disease, and their offspring as well.

Sidebar: Genetics of brisket disease in cattle

While brisket disease has a genetic component, little is understood about how it passes

between generations, andit seems to be able to skip generations, says Rich McCormick,

University of Wyoming professor of muscle biology. Thats one reason why you cant entirely

get rid of it by using the PAP test. Youll miss some animals that carry it and it may turn up

in a later generation.

McCormick says some producers report buying an untested bull that did fine at higher

elevations and produced progeny free of brisket disease. However, later offspring developed

brisket disease. Exactly how and why the condition expresses itself isnt understood, he says.

Even if you could estimate the percent of offspring of a certain animal that might inherit this

susceptibility, you dont know when it might occur.

Sidebar: Its important to test for brisket disease in cattle

Most seedstock producers at low elevations dont test animals they sell. Producers in

Wyoming, Colorado and nearby states, however, generally use the PAP test to reassure

customers that their animals are free of this problem.

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Its crucial for high-altitude producers to use tested seedstock, or death losses may become a

huge issue, says Rich McCormick, University of Wyoming professor of muscle biology.

In one instance, semen from an untested sire was used on 200 cows, and 75% of his

progeny developed brisket disease, he says. For all his virtues, a great bull may not work athigh elevation. If that sire has never been PAP-tested, youre running a risk.

Colorado State University DVM Tim Holt says a complicating factor is that testing has

historically focused on the bull side, overlooking females. On some ranches, however, the

females may be more indicative of the problem than the males, with some cows potentially

being carriers (passing genetic susceptibility to their calves) without developing clinical

signs themselves, he says.

Sidebar: Treatment of Brisket Disease in cattle

The best treatment for an animal with brisket-disease symptoms is to immediately take it

to lower elevation, or treat it in a hyperbaric chamber where oxygen concentration can be

greatly increased, to simulate lower elevation, says Tim Holt, Colorado State University

DVM.

Other treatments that keep the animal from dying until it can be taken to lower elevation

include diuretics to lower blood pressure and fluid volume.

You treat these animals like you would a human patient with right-side congestive heartfailure. You put them on Lasix (a diuretic), eliminate fluid and salt intake, and administer

broad-spectrum antibiotics and a vitamin B complex. You can also drain the chest cavity,

inserting a large-diameter needle through the chest wall, between the ribs, he says.

Fluid observed on the outside (swelling in brisket and neck) is just a small part of the total.

Theres even more fluid inside the thoracic cavity putting pressure on heart and lungs.

Draining this can relieve the animal, but you still must take it to lower elevation, Holt

stresses.

A current study is looking at other treatments for acute cases such as various medications

to reverse the condition or treatment for the hypertension, he adds.

But were still PAP-testing replacement heifers and bulls for use in high-altitude areas.

Even though its not the greatest test, its still the best we have for determining which

animals are at risk.

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