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The basics of chicken farming (in the tropics) Part 4 of 4

By goGreen | November 22, 2011
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Common drugs in poultry

Chloramphenicol

Flumequine (Flumic contains 3% flumequine)

3  Neomycin

4  Nitrofuranes

furoxone } in feed 100-200 ppm
nitrofurantoïne }
in water – 2 ml of a 3% suspension per ltr

All waterbirds receive the half dose. In all birds they decrease leucocyte production. Can lower the hatching percentage.

Furoxone

Nitrofurantoïne (furadantine)

Penicillines

Ampicilline

Sulfa drugs

7  Tetracyclines:

Drinking water 1 g/ltr gives a therapeutic bloodlevel, e.g. against E. coli; for intestinal action 0.2 g/ltr water. Rapid absorption. Tetracycline gives the highest blood-level

9 Diseases caused by parasites

9.1 Coccidiosis
Coccidiosis is the most common contagious disease in chicken farming. It is caused by several coccidium species which generally affect the intestinal tract of the chickens. The symptoms vary from acute death mainly in young birds, to suboptimal production in all ages (that is to say, production is not what it should be). Coccidiosis is caused by coccidia (singular coccidium) which are protozoa, one-celled parasites. Where there are chickens there are coccidia!

Economic losses can be enormous. Large-scale chicken farming only became possible after the discovery of coccidial drugs.  Wire floors (or slatted) were mainly introduced to prevent coccidiosis. Coccidiosis is the main single reason for suboptimal production. Already slight infection of the small intestine in broilers reduces their growth. The preventive use of anti-coccidiosis drugs in broilers and rearing stock represents quite a lot of money.

Coccidiosis is not only a disease of chickens, it occurs in all types of poultry. And, for instance, it can also affect goats kept under intensive husbandry in goat houses. However, chickens have their own specific coccidia types which do not cross-infect other (bird) species.

In the chicken are nine species of coccidia, of which five are important. They are:
1 Eimeria (E.) acervulina very common, often subclinical
2 E.maxima mainly subclinical
3 E.necatrix together with tenella the most pathogenic species
4 E.tenella very common and pathogenic
5 E.brunetti

The coccidium life-cycle is complicated and not exactly the same for the five species. There are three stages in the cycle. The first stage is an enormous, non-sexual multiplication inside the host. After that there is formation and fertilization of so-called oocysts, also inside the host. The oocysts are expelled with the faeces. Under favourable conditions the oocysts then  sporulate (they form so-called sporozoites) and become infective for chickens. Only sporulated oocysts cause infection. The period of the cycle inside the host lasts 4-5 days (minimum) and the sporulation time under favourable conditions is 1-2 days. The total of the cycle is therefore 5-7 days, under favourable conditions.

Sporulation time depends on the factors (a) temperature, (b) humidity and (c) oxygen availability:

temperature
The optimum temperature is about 28 °C and about 90% of the oocysts will then sporulate in 1-2 days (if moisture conditions are right). Each coccidium species has its own range of temperature for oocyst development, e.g. E.tenella = 12 to 33 °C. Temperatures lower than the minimum temperature conserve the oocysts and there is no development.

moisture
Too dry means ‘no development’. Good litter contains 17-35% moisture. Ideal conditions for the development of immunity in the chickens is litter with 30-35% moisture. When it is too dry for sporulation the oocysts slowly die.

oxygen
There is seldom a lack of oxygen and 10% of air oxygen pressure is already sufficient for sporulation.

Oocysts are difficult to kill. Their resistance is high, especially in a humid and cool environment. In litter oocysts are affected by dryness, high temperatures, ammonia, lack of oxygen and bacterial toxins.

Disinfectants in general have little influence, but ammonia kills in high concentration (5-10%); a combination of lime + ammonium sulphate (fertilizer quality) is effective in this respect.

Infection
Direct contact cannot infect the birds.
The chickens ingest the sporulated oocysts by eating and drinking. The infection is carried by contaminated buildings, the farm yard, litter, dust, contaminated feed and water, objects and persons. Also insects can transmit oocysts. Introducing new chickens always means introducing coccidia.

infection pressure
The ‘infection pressure’ of coccidia depends on several factors, indicated as follows:

The ‘pressure’ also depends on the species: acute disease results after infection with 500,000 sporulated oocysts of E.acervulina but with only 10,000 oocysts of E.tenella.

Within the coccidia species there are differences in pathogenicity. Mixed infections are common but generally one species strongly predominates.

Infections are often farm-linked; coccidiosis is a management disease!

The disease process
Acute outbreaks with rapid deaths are possible. In that case a large number of sporulated oocysts have been taken up (ingested) by the flock, in a short time.

The coccidia cause damage to the tissue forming the outer layer (= epithelium) of mucous membrane in the wall of the intestines of the chickens. The damage is mainly mechanical although there is production of toxins.

Tenella and necatrix cause haemorrhages, inflammation and epithelial loss; tenella in the caeca, necatrix in the small intestine (middle third part). Maxima and brunetti cause epithelial loss and sometimes small haemorrhages; maxima in small intestine, brunetti in colon, cloaca, last part of small intestine and first part of caeca. Acervulina cause epithelial destruction without haemorrhages.

The pathological effects are:

The result is that even subclinical infections already have a  distinctive negative effect on appetite, condition, production, feed conversion and health. In more severe cases the result is sick animals, rough feathers, diarrhoea by enteritis and mortality.

Immunity and resistance
Immunity is important and is more present in older birds. Because of the establishment of immunity, coccidiosis is mainly a problem in young chickens. The immunity to coccidiosis is so-called species-specific; this means that a chicken can suffer from coccidiosis as often as five times (because there are five E.species).

The development of immunity depends on several factors:

as illustration: a mild infection of maxima gives good immunity but necatrix requires several reinfections to obtain good immunity

Older birds without immunity are more susceptible than young birds. Outbreaks of coccidiosis in broilers of a certain age cause more growth depression than in young birds. Immunity can stop the cycle of development of a coccidium; with strong immunity there is no development at all. Other infections e.g. Gumboro, worms, management errors, stress, etc., lower the overall resistance of the birds and often initiate an outbreak of coccidiosis.

Oocyst excretion
0ocyst excretion in a flock often lasts only a few weeks because of the development of immunity. Large differences in oocyst production exist between species; it decreases in the following order: acervulina > tenella > brunetti > maxima > necatrix.

In an acute outbreak of disease, especially of necatrix and tenella, severe symptoms can precede the production of oocysts.

9.1.1 A brief discussion of the five Eimeria species affecting chickens

Eimeria acervulina: chronic, subclinical, low mortality
Affects first half of small intestine. The cycle is completely performed in the epithelial cells; here oocysts can often be seen with the naked eye. Lesions are caused mainly by the huge number of oocysts of which more than one can develop in the same cell. Relapses are no exception because of the enormous contamination of the environment with oocysts, and the weak immunity.

Symptoms: in all ages, but often in older broilers and young layers. Many infections are subclinical or chronic (name: chronical coccidiosis). In severe cases there is poor feed conversion, suboptimal growth and production, slightly increased mortality, pale and thin birds.

Organ damage: thickening of the wall of first part of small intestine, flaky turbid content, never haemorrhages. In severe cases white striations (= linear marks) can be seen which are accumulations of oocysts and other stages, in the intestinal wall. In mild cases red mucous membranes.

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Topics: Agri-Business, Farming Methods, Poultry | Comments Off

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