Leg Problems in Broilers and Turkeys

Leg Problems in Broilers and Turkeys
PUBLICATION DATE: 26/05/2008
RATING
AUTHOR: R. Scott Beyer, Poultry Specialist, Animal Sciences and Industry - Kansas State University Agricultural Experiment Station and Cooperative Extension Service
Leg problems can occur in fast-growing strains of broilers and turkeys. These disorders are not unique to small flocks; they also occur in commercial broiler and turkey flocks. Estimates of the incidence of leg and foot problems range from 0.5 to 4 percent of all broilers grown.


What is a leg problem?

Some birds may develop crooked legs, toes and feet; bowlegs; twisted joints; or swollen hock joints between the drumstick and the foot. Most are not severely affected and will grow quite normally. Others are more severely affected and may not be able to stand, or their feet may deviate drastically from their normal position. Birds with leg problems so severe and painful that they are unable to obtain food should be terminated.

Wide fluctuations in occurrence and multiple pathological conditions indicate that leg disorders are caused by many factors. Selection for rapid growth may add to this problem because of the increased stress on the skeletal, muscular, and tendon tissues of the birds.


What causes leg problems?

An average weight gain of 4.25 pounds in seven weeks, a high ratio of white to dark muscle, stress, and improper management may lead to leg problems. The largest, fastest growing males in the flock are usually the ones affected. Although a small percentage of birds may be predisposed to leg problems, use of highly selected fast-growing strains is recommended because savings in feed costs and time far outweigh the loss of a few birds.

Infectious agents also have been identified as direct or indirect causes of leg disorders. Staphylococcus and viral arthritis/tenosynovitis are two common agents. Leg disorders caused by these agents can be easily confused with nutrition-related conditions.

If hatching your own chicks, be sure they have a firm surface to stand on while inside the incubator. It takes a few hours after hatching for their leg muscles to function fully. Slippery surfaces also may lead to leg problems.

Many leg disorders of Kansas broilers appear to be the result of nutritional deficiencies. Broilers need a well-fortified starter ration that contains 22 to 24 percent protein. Certain adjustments may be necessary if a lower protein, such as 20 percent starter ration, is all that is available. Equal parts of a 20 percent protein chick starter and 28 percent protein gamebird starter will provide a 24 percent protein ration.

If this option is not available, protein supplements such as meat meal or fish meal can be used to fortify low-protein starter rations. Have the local K-State Research and Extension agricultural agent help you formulate this mixture.

Other nutrition-related causes of leg disorders include switching from starter ration to grower ration too soon, or diluting the starter ration with cereal grains. Never dilute a complete ration with cereal grains unless specified on the product label. Either practice results in dilution of the nutrients in the rations, which can result in leg disorders from nutritional deficiencies.


Rickets

Rickets is a condition characterized by a lack of mineralization of the bone caused by a calcium, phosphorus, or vitamin D deficiency. A vitamin D deficiency is the most probable cause and can be due to a mixing error, under fortification, or the presence of mold toxins that interfere with normal metabolism. Rickets resulting from a phosphorus deficiency may be due to insufficient available phosphorus in the ration. A calcium deficiency is not common when standard ingredients are used.


Perosis

Symptoms of perosis include swelling of the hock joints, slipped tendons, and severe shortening of the long bones. Deficiencies of the trace minerals manganese and zinc and the vitamins choline, niacin, folic acid, biotin, and pryridoxine can produce a perosis-type condition. Birds fed complete rations with a mineral premix rarely have perosis.


Tybial Dyschondroplasia

Many fast-growing birds may develop tybial dyschondroplasia (TD). This problem is most associated with bone growth that is so rapid that it exceeds the capacity of the bird’s system to put calcium into the bone. When the bird gains weight, the growth plate twists or fractures. This condition worsens if the calcium to available phosphorus ratio is incorrect. It should be about 2 parts calcium to 1 part available phosphorus.


Fast- vs. slow-growing

Recently, a lot of interest has developed for breeding slower-growing strains of meat-type birds. Research indicates that slower-growing birds often have fewer leg problems. For some producers the problem with slower growing birds is that they take longer to reach body weight. A fast-growing strain of bird should be ready for processing in 6 to 8 weeks compared to the slower strains, which will need 12 to 15 weeks. Birds that take longer to grow have a greater chance of dying from other causes and require more time and labor.


What to do

Most treatments are not likely to correct the problem. An exception is the use of a water-soluble vitamin mixture in the drinking water and the addition of a trace mineral mix to the feed. This treatment may be beneficial if administered at the first signs of trouble. A positive response indicates a higher fortified ration is in order. A complete ration from a commercial manufacturer does not require vitamin or mineral supplements.

Minimize the potential for leg disorders by following good management and sanitation practices, using quality rations, and minimizing stress.

One alternative to consider is using fast-growing strains, and growing them slowly. This can be done by feeding less concentrated rations or by limiting feed intake. Many fast-growing strains are grown in 24 hours of light. Turning the lights off for a few hours each night will limit feed intake. Be sure to ask your hatchery exactly what breed they are producing and choose proper management strategies.

If steps have been taken to reduce the occurrence of leg problems, don’t panic if a few birds in the flock are affected. Many of these birds will continue to grow and can be processed.

If the problem persists, a laboratory diagnosis of the condition is needed because of the difficulty in distinguishing between infectious and nutritional causes in the field.


A diagnosis can be obtained by shipping a sample of two or three affected birds to the Kansas State University Veterinary Diagnostic Laboratory.

If the birds cannot be delivered alive, they should be sacrificed, placed in a waterproof plastic bag, packed in ice in a foam cooler, and shipped by courier.

Refer to K-State Research and Extension publication Prevention Control of Poultry Diseases, L-754, for more information.
PUBLICATION DATE: 26/05/2008
RATING
AUTHOR: R. Scott Beyer, Poultry Specialist, Animal Sciences and Industry - Kansas State University Agricultural Experiment Station and Cooperative Extension Service

Advice on Reducing Heat Stress in Poultry

Advice on Reducing Heat Stress in Poultry

Dealing with summertime heat is a great challenge for people in Louisiana. LSU AgCenter poultry specialist Dr. Theresia Lavergne says high heat and humidity combine to pose severe problems for all types of poultry.

"Under conditions of severe heat stress, poultry will have a reduced growth rate, decreased feed intake, poor feed conversion, decreased egg production, reduced hatchability rate, reduced egg shell quality, reduced egg size and reduced internal egg quality," Lavergne explained. "Additionally, heat stress can cause increased mortality."

All types and ages of poultry are susceptible to heat stress, but older poultry face a bigger risk. As poultry get older, they increase in size as well as insulation (feathering). Lavergne says this makes it harder for them to dissipate heat.

"The most obvious sign of heat stress in poultry is panting," the LSU AgCenter specialist says. "Poultry do not have sweat glands that can cool their skin, so instead they must use evaporation from their throat and respiratory system as a means of cooling themselves."

Lavergne points out that panting takes a lot of energy which, in turn, generates an appreciable amount of body heat for poultry.

"Ultimately, if poultry are not relieved of heat stress, their body temperature can continue to rise and increase the possibility of mortality," she stresses, "Fortunately there are several things you can do to help your home poultry flock handle heat stress."

* Provide cool, clean, quality drinking water to your poultry. Water must be available at all times and must be in a location that is easily accessible to your poultry. Water will help keep your birds cool.

* Provide a comfortable environment for your poultry. Always make sure your poultry are in a well-ventilated area in which there is nothing to obstruct the airflow. Placing poultry in a well-ventilated area will help reduce the incidence of heat stress. In addition, a misting/fogging system can be used in a well-ventilated area to help the birds cool themselves.

* Provide feed during the coolest part of the day. Poultry produce heat during the process of digestion, and when this heat is combined with the significant rise in body temperature that occurs during the late afternoon of a hot day, there is a greater risk of heat stress for poultry.

* Supplement drinking water with electrolytes. During true heat stress, the electrolyte balance in birds is altered as a result of panting. The addition of electrolytes to the drinking water will help balance the electrolytes in the birds and increase the birds’ water intake. The increased water intake will aid in cooling the birds and will improve the evaporative cooling of the birds. However, you should consult your veterinarian before using any heat stress supplements such as electrolytes.

* Avoid overcrowding your poultry. You should reduce the number of birds kept in a house or in an area. Birds produce body heat. Thus, by reducing the number of birds in a house you will reduce the amount of body heat produced in the house.

* Avoid excessive activity during the hottest part of the day. The hot weather is a great stress on the birds, so avoid bothering and disturbing the birds during periods of peak heat.

"The heat of the summertime is unavoidable," Lavergne said. "However, by recognizing the signs of heat stress and taking steps to prevent heat stress in your home poultry flock, you can help keep your poultry comfortable and productive during the summertime."
Source :http://www.lsuagcenter.com/en/crops_livestock/livestock/animal_health/poultry/Advice+on+Reducing+Heat+Stress+in+Poultry.htm

Heat Stress Management in Broilers

Heat Stress Management in Broilers

Introduction
High ambient temperatures coupled with high humidity can be devastating to commercial broilers. Heat stress interferes with the broilers comfort and suppresses productive efficiency. Although increased heat is seen as a major problem in poultry production, studies show that it is not only the excessively high temperatures, but also the fluctuation of the temperature. This naturally occurs during the temperature change from daytime to nighttime. Recent studies have shown that broilers tend to perform reasonably well in a high, but constant environment of 380C (100oF), but become stressed when fluctuating temperatures exist. When temperature fluctuations occur, birds need to use more energy in an attempt to maintain their body temperature of 41-420C (106-108oF). When their body temperature rises above 420C (108oF), mortality begins to occur. It is important to be aware of the temperature in the shed, and be conscious of how much it may fluctuate.
During periods of heat stress the broiler has to make major thermo-regulatory adaptations in order to prevent death from heat exhaustion. The result is that the full genetic potential of the broiler is often not achieved. The purpose of this paper is to review some of the effects of heat stress on broilers and methods, which can be used by the poultry producer to partially alleviate some of the detrimental effects of heat stress on broiler performance.
Physiological response to heat stress
Broilers subject to high environmental temperatures exhibit many behavioral changes which allow them to re-establish heat balance with their surroundings. Broilers rest more during periods of heat stress. Some birds will stand quietly while others simply crouch near walls or waterers. Usually, their wings are spread away from the body to promote cooling by reducing body insulation. Within the bird, blood flow is diverted from certain internal body organs such as the liver, kidneys and intestines to dilated blood vessels of the peripheral tissue (skin) in order to facilitate heat loss.
Hyperventilation or "panting" increases during periods of high environmental temperature. Heat loss through evaporative cooling allows the broiler to dissipate the heat it is generating. However, panting requires increased muscle activity and these results in an increased energy requirement, which is associated with heat stress. Therefore, decreased energy efficiency also accompanies hot weather. Panting would normally be expected to occur when the ambient temperature is near or above 30oC.
Relative humidity influences evaporative heat loss through panting. Broilers, as well as other domestic poultry, cannot tolerate high temperature coupled with high relative humidity. Death due to heat exhaustion will occur very quickly, especially in heavier birds, if both temperature and humidity are high. In normal birds, panting will remove approximately 540 calories per gram of water lost by the lungs.
Importance of panting
Normally, blood pH is controlled by the lungs and kidneys along with the various buffer systems, which prevent rapid changes in the pH. However, as the respiratory rate increases in heat stressed broilers, there is a corresponding decrease in the levels of blood carbon dioxide. Respiratory alkalosis (elevated blood pH) results. Heat stress also depletes potassium and other minerals in the body, altering the delicate electrolyte balance in the body.
Feed intake Vs Heat stress
Broilers maintained in hot environments reduce their feed consumption. This is a part of their physiological adaptation to heat stress. The reduction in feed intake results in a decrease in the daily intake of nutrients responsible for growth. However, fewer nutrients to metabolize means less heat produced by the body. Thus, even though growth is slowed, the broiler can now more easily cope with the heat because of the lessened need for heat dissipation. Research data clearly shows that the survival rate of broilers decreases as feed intake increases during heat stress, especially during the hottest part of the day.
Importance of fasting during heat stress
In addition to heat-stress mortality, economic losses associated with broiler heat stress also occur as a result of lowered growth rate and decreased feed efficiency. Therefore, it is natural for producers to want to stimulate feed consumption in hot weather. However, any management technique, which promotes feed consumption or increased activity during the peak hot periods may be counterproductive. The extra feed consumed will increase the bird's heat load and probably result in additional mortality. Fasting the broiler prior to or during peak hot periods of the day lessens the heat load and enhances survival.
Fasting reduces the heat production from digestion, absorption and metabolism of nutrients. Fasting also has a calming effect. Movement in animals occurs through muscle contraction which generates heat. In hot environments this heat production only adds to the heat load. Therefore, to lessen the heat load, broilers should be kept as calm as possible. This is especially important during the hottest parts of the day. Once the hottest periods are over and ambient temperature starts to fall, the broilers will usually begin consuming feed again.
Five Tips For Handling Heat Stress
1. Add nutritional supplements to the feed or water.
The electrolyte balance in birds is altered during heat stress due to panting. Panting increases carbon dioxide loss in the bird, which reduces the birds’ ideal water intake. By adding electrolytes to the feed or water, birds increase their water intake, which aids in keeping a constant body temperature and maintains an effective system of evaporative cooling.
2. Carefully select a proper time of feeding and withdrawing feed.
During the late afternoon there is a significant rise in body temperature, which, if severe, may kill the bird. The late afternoon may not be the hottest time in the day, but it is the peak of digestion in birds when eating in the early-mid morning period. A good management strategy for layers to aid in reducing heat stress is to withdraw feed prior to the anticipated time of peak temperature so that it may take an unneeded heat load off the bird. For broilers, a period of darkness in the late afternoon can be used to avoid excessive activity. If using a feed withdrawal program, it can be beneficial to give supplemental lights during the period of natural darkness.
3. Have readily available drinking water
Ensure that the water is clean and of optimum quality. Water must be readily available and have nipple drinkers at the right height. Adding nutritional water supplements that run continuously in hot weather is also of great benefit.
4. Ensure good ventilation.
By providing the birds with a comfortable environment, common stressors and heat will reduce. Always check airflow patterns and keep your ventilation system well cleaned. Misting systems can also be used to help aid the birds in their own cooling mechanisms.
5. Dietary modification during heat stress
Heat stress causes broilers to decrease feed intake and consequently nutrient intake. Therefore, the dietary nutrient concentrations should be increased. Simply increasing the protein concentration is the wrong approach. The energy content of the diet, along with other nutrients, should be increased. Increasing fat calories should be considered. Dietary vitamin and mineral concentrations should be re-evaluated. The use of vitamin C, as an anti-stress agent, is often considered during periods of heat stress. Choosing the correct coccidiostat is very important as well as the use of antioxidants and mold inhibitors in stored feed. Protein contributes more to metabolic heat production than do carbohydrate and fat. Therefore, feeding imbalanced diets with regards to amino acids will result in increased metabolic heat production. Amino acid balance in the diet is especially important. Efforts should be made to formulate diets with slightly lower protein levels and to utilize synthetic amino acids, especially methionine and lysine.
Summary
Broilers under heat stress have to make critical physiological adjustments. Feed intake is depressed and water intake is increased. Dietary adjustments can help reduce metabolic heat production and maintain nutrient intake. Energy intake and amino acid balance is of extreme importance in heat stress. Providing adequate ventilation and stimulating water consumption is essential. Minimizing bird activity during the hottest parts of the day lessens the heat burden. Controlled fasting is beneficial and usually increases survival rate of broilers during heat stress.
Source :http://www.neospark.com/neospark/images/Heat%20Stress.PDF

Level Gas Secara Umum Pada Kandang Unggas

Gas	Simbol	Keterangan
		Mematikan	Diinginkan
Karbon Dioksida	CO2	Diatas 30 %		Dibawah 1 %
Metana	CH4	Diatas 5 %		Dibawah 1 %
Amoniak	NH3	Diatas 500 ppm		Dibawah 40 ppm
Hidrogen Sulfida	H2S	Diatas 500 ppm		Dibawah 40 ppm
Oxygen	O2	Dibawah 6 %		Diatas 16 %

Bagaimana Antibiotika Bekerja ?

Banyak orang tahu dan sering mendengar tentang antibiotika, akan tetapi belum tentu memahami apakah sebenarnya antibiotika itu. Antibiotika pertama yang dikenal adalah penisilin, dimana zat ini dihasilkan oleh jenis jamur penicillium. Dalam sejarah antibiotika orang yang patut di kenang adalah A.Fleming, karena beliau yang pertama menemukan penisilin (Tahun 1929) akan tetapi penggunaannya sebagai zat pembunuh bakteri baru banyak digunakan pada tahun 1943, dan seiring dengan perkembangan teknologi sekarang telah dikenal ratusan antibiotika .

Pembagian Antibiotika Berdasarkan Cara Kerjanya

Antibiotika dalam hal ini dibagi dua :

1. Antibiotika berspektum luas : antibiotika yang efektif digunakan bagi banyak spesies bakteri, baik kokus,basil maupun spiral, contohnya tetrasiklin (Mampu membunuh bakteri berbentuk kokus,basil dan spiral).
2. Antibiotika berspektum sempit : antibiotika yang efektif digunakan untuk spesies tertentu, contohnya penisilin (Hanya mampu memberantas bakteri berbentuk kokus).

Sifat-sifat Antibiotika

Antibiotika haruslah memiliki sifat-sifat sebagai berikut :

1. Menghambat atau membunuh patogen tanpa merusak inang (Host).
2. Bersifat bakterisida dan bukan bakteriostatik.
3. Tidak menyebabkan resistensi pada kuman.
4. Berspektrum luas.
5. Tidak bersifat alergenik atau menmbulkan efek samping bila dipergunakan dalam jangka waktu yang lama.
6. Tetap aktif dalam plasma, cairan badan atau eksudat.
7. Larut dalam air serta stabil.
8. Bakterisidal Level, di dalam tubuh cepat dicapai dan bertahan untuk waktu lama.

Mekanisme Kerja Antibiotika

Antibiotika menggangu bagian-bagian yang peka didalam sel, untuk lebih jelasnya dapat dilihat pada penjelasan dibawah ini :

1. Antibiotika yang mempengaruhi dinding sel.

Pada dasarnya sel kuman dikelilingi oleh dinding sell yang melindungi membran protoplasma dibawahnya dari trauma. Pada kondisi ini antibiotika bekerja untuk mengganggu pembentukan dinding sel terutama pada tahap akhir, sehingga terbentuklah steroplas, yakni kuman tanpa dinding sel (Terjadi pada golongan penisillin).

2. Antibiotika yang mengganggu fungsi membran sel

Antibiotika yang masuk kedalam golongan ini adalah polimiksin, kolistin, nistatin dan amfoterisin B. Antibiotika golongan ini merusak dan memperlemah dinding sel, dimana perlu diketahui bahwa membran sel merupakan hal yang sangat vital dalam sel karena berfungsi sebagai selektif permeabel, pengangkutan aktif dan mengendalikan susunan sel.

3. Antibiotika yang menghambat sintetis protein

Yang termasuk didalam golongan ini adalah aktinomisin, rifampisin, steptomisin, tetrasiklin, kloramfenikol, eritromisin, klindamisin, linkomisin, kanamisin, neomisin, netilmisin dan tobramisin, dan mekanisme kerjanya sebagai berikut ;

- Aktinomisin : sangat aktif terhadap bakteri gram positif dan negatif.

- Rifampisin : mempunyai spektum antibakteri yang luas dan terutama efektif terhadap bakteri gram positif dan mikrobakteria.

- Streptomisin : bakteri bersifat bakterisida tehadap sejumlah besar bakteri-bakteri gram negatif dan positif.

- Tetrasiklin : mempunyai spektrum sangat luas, mencakup spektrum penisillin, streptomisin dan kloramfenikol.

- Kloramfenikol : bersifat bakteriostatik aktif terhadap sejumlah bakteri gram positif dan gram negatif, rikettsia dan klamidia.

- Eritromisin : termasuk sebagai antibiotika makrolida, dapat bersifat bakteriostatik atau bakterisida, merupakan obat pilihan terhadap mycoplasma dan juga untuk stafilokokus, streptokokus Grup A.

- Klindamisin : banyak digunakan terutama untuk infeksi bakteri anaerob.

4. Antibiotika yang menghambat sintetis asam nukleat

Yang termasuk di dalam golongan ini adalah : asam nalidiksat, novobiosin, pirimetamin, sulfonamida dan trimetoprim. Merupakan penghambat efektif terhadap sintetis ADN, dimana akan membentuk ikatan kompleks melalui ikatan-ikatan pada residu deoksiguanosin.

Penggunaan Antibiotika Dilapangan

Beberapa peternak dalam menghadapi suatu kasus atau penyakit tanpa berpikir panjang menggunakan antibiotika berspektum luas dengan alasan bahwa dengan penggunaan antibiotik yang berspektrum luas semua bisa teratasi. Selain masalah tersebut diatas juga peternak sering menggunakan preparat antibiotik yang sama dari satu periode pemeliharan ke periode berikutnya ( Sebaiknya preparat antibiotika yang dipakai dalam suatu farm diganti tiap 3 – 4 periode pemeliharaan).

Hal-hal yang perlu di pertimbangkan dalam penggunaan preparat antibiotika dalam menangani kasus penyakit dalam lingkungan Farm :

1. Penyebab infeksi atau penyakit yang terjadi harus diketahui ( Apakah dari golongan Bakteri atau virus ).
2. Tingkat morbiditas harus diketahui.
3. Umur ayam.

Stress Vs Vitamin C Pada Unggas

Pada ternak unggas jika terjadi stress maka kemampuan yang mereka miliki tidak bisa tampak secara maximal olehnya itu kondisi optimal dalam pemeliharaan unggas harus dipertahankan agar dapat mendapatkan hasil produksi yang maximal, untuk lebih jelasnya mari kita menyimak uraian dibawah ini.

Stress

Stress didefinisikan sebagai ketegangan secara fisik atau secara psikologis. Stress pada unggas dipengaruhi oleh banyak faktor, diantaranya tekanan eksternal seperti nutrisi pakan, perubahan ransum secara tiba-tiba, perubahan air minum, luas kandang, tingkat produksi, jumlah unggas yang dipelihara secara tiba-tiba, perkandangan, pemeliharaan rutin, transportasi, kegaduhan, adanya orang yang tidak dikenal, sakit, kelelahan, manajemen, temperatur dan perubahan cuaca secara tiba-tiba (Ensminger, 1992).

Menurut Kilgour dan Dalton (1984) batasan praktis terhadap stress adalah terjadinya perilaku abnormal, turunnya konsumsi pakan, produksi rendah, timbulnya penyakit dan kematian. Cekaman merupakan respon yang timbul apabila ternak dihadapkan pada suatu perubahan lingkungan. Sifat nervous akan meningkat kepekaannya terhadap terjadinya cekaman dari pengaruh lingkungan, karena cekaman secara biologis adalah berbagai reaksi yang dilakukan hewan untuk memelihara integritas proses-proses fisiologis di dalam tubuh. Perlakuan dalam pemeliharaan akan berdampak pada timbulnya cekaman seperti perkandangan, pemberian pakan dan minum, kegaduhan dan dampak pemeliharaan secara intensif lainnya. Indikator terhadap cekaman ringan secara fisiologis dapat diamati terjadinya perubahan atau peningkatan dari unsur hematologis, endokrinologis, metabolisme maupun perilaku ternak. Secara fisiologis perubahan-perubahan akibat cekaman pada unggas terjadi pada kelenjar adrenal ( hypertropi, kadar kolestero menurun, sintesis kortikosteroid meningkat, kandungan asam askorbat menurun); darah (kolesterolemia, NPN meningkat, Ca++ meningkat, rasio Na++ dan K+ berubah, kortikosteroid meningkat, glukosa meningkat, heteropilia, limfopenia) dan jaringan limfoid (involusi bursa fabricius, involusi thymus, level antibodi menurun) (Siegel, 1971; Freeman, 1967; Ringer, 1976). Akibat tidak langsungnya pada cekaman berat akan menyebabkan perilaku yang tidak normal, menurunkan konsumsi pakan, produksi rendah, penyakit dan kematian sehingga dapat menurunkan kinerja produksi (Kilgour dan Dalton, 1984).

Vitamin C Sebagai Antistress

Vitamin C lebih dikenal sebagai asam askorbat karena sifatnya yang asam dan efektifitasnya dalam pengobatan skurvi. Selanjutnya Padue dan Thaxton (1986), melaporkan bahwa suplementasi vitamin C berpengaruh terhadap pertumbuhan, reproduksi, mortalitas, dan berpengaruh positif terhadap unggas yang mengalami cekaman lingkungan dan gizi. Sifat asam disebabkan oleh dua hidroksilenoat yaitu hidroksil pada C-3 dan C-2 (Delgado, 1982). Vitamin C merupakan struktur paling sederhana, merupakan senyawa dengan rumus bangun yang menyerupai suatu monosakarida dan dalam kenyataan vitamin C secara biokimia disintesa dari D-glukosa (Brown, 1976). Vitamin C tergolong senyawa yang larut dalam air dan bersifat tidak stabil, serta mudah teroksidasi selama proses pembuatan dan penyimpanan pakan.

Pardue dan Thaxton (1986) menyatakan bahwa vitamin C (asam askorbat) belakangan dikenal sebagai antistress yang baik dan banyak dimanfaatkan pada unggas karena dibutuhkan dalam reaksi hidroksilasi pada sistem syaraf dan medulla adrenal. Vitamin C sebagai kosubstrat dalam hidroksilasi tirosin pada pelepasan norepineprin dan dalam medulla adrenal untuk pelepasan kotekolamin lain yaitu epinefrin. Peranan ini penting untuk fungsi sistem syaraf secara normal dan untuk ketersediaan epinefrin dalam hubungannnya dengan stress (Linder, 1992). Menurut Piliang (2001) suplemen vitamin C dalam jumlah banyak diperlukan jika tubuh dalam kondisi stress karena secara emosional atau cekaman lingkungan, untuk mempertahankan konsentrasi asam askorbat yang normal dalam plasma darah. Hal ini sesuai dengan pendapat Hornig dan Frigg (1979) ayam tidak mempunyai kemampuan lagi untuk mensintesis vitamin C dalam jumlah yang cukup apabila mendapat cekaman panas.

Kadar vitamin C dalam plasma dan hati menurun dengan bertambahnya umur. Pada saat menetas kecepatan sintesis vitamin C pada ginjal ayam masih lambat, tetapi setelah itu akan meningkat beberapa kali lipat sampai umur 20 – 30 hari dan menurun setelah di atas umur 30 – 40 hari (Hornig dan Frigg, 1979).

Penelitian penanggulangan cekaman dengan pemberian vitamin C pada broiler, ayam petelur yang sedang produksi dan ayam hutan hijau telah dilakukan di Indonesia. Ichsan (1991) melaporkan bahwa pemberian vitamin C pada suhu ruang 33^oC tidak memberikan pengaruh yang berarti terhadap kecepatan pertumbuhan. Pengaruh yang menonjol adalah pada peningkatan daya tahan cekaman panas yang ditandai dengan lebih rendahnya angka kematian pada broiler yang diberi vitamin C dibandingkan dengan yang tidak diberi. Habibie (1993) dalam kesimpulan laporannya menyatakan bahwa suplementasi vitamin C pada ayam petelur tipe medium fase produksi I dan fase produksi III secara nyata meningkatkan produksi telur (hen day), menurunkan konversi ransum dan tidak berpengaruh pada konsumsi pakan, berat dan kerabang telur. Suplementasi vitamin C sebanyak 1000 ppm pada fase produksi III memberikan respon yang lebih tinggi dan memberikan keuntungan lebih besar dibandingkan pada fase produksi I. Widjajakusuma (1999) melaporkan bahwa pemberian vitamin C dosis tinggi atau kombinasi dengan serbuk pinang pada ayam hutan hijau pada umumnya dapat memperbaiki kinerja reproduksi dan hematologis sebagai indikator tertanggulanginya cekaman.