Environmental Hygiene PDF

‫‪Environmental‬‬ ‫‪Hygiene‬‬ ‫‌أ‪ ‌.‬د‪‌.‬سطوحي‌أحمد‌سطوحي‌‬ ‫أستاذ‌صحة‌الحيوان‌والدواجن‌والبيئة‌‬ ‫كلية‌الطب‌البيطري‌‪-‬جامعة‌أسيوط‌‬ ‫‌‬ ‫)‪I‬‬ ‫‪Air Hygiene‬‬ ‫‌‬ ‫‌‬ ‫‌‬  Gas %...

‫‪Environmental‬‬ ‫‪Hygiene‬‬ ‫‌أ‪ ‌.‬د‪‌.‬سطوحي‌أحمد‌سطوحي‌‬ ‫أستاذ‌صحة‌الحيوان‌والدواجن‌والبيئة‌‬ ‫كلية‌الطب‌البيطري‌‪-‬جامعة‌أسيوط‌‬ ‫‌‬ ‫)‪I‬‬ ‫‪Air Hygiene‬‬ ‫‌‬ ‫‌‬ ‫‌‬  Gas % ‌ ‌ ‌ ‌ ‌ Normal constituents of Air: A mixture of coulourless and odourless gasses, constant in quantity. At 0 °C and 760 Hg has the following constituents:-  Nitrogen 78.03 Oxygen 21.00 Carbon dioxide 0.03 Agron 0.94 Inert gasses ( Neon, Traces helium, Krypton, Xenon, Ozone, Hydrogen, Nitrogen oxide, Nitrous oxide, ammonia, others Why composition remains fixed: 1. Immensity of the atmosphere. 2. Continuous exchange of gasses between animals and plants.  3. Mixing of air by air currents. Carbon dioxide (CO2): Normal atmosphere contains 0.03% (300ppm). Maximum permissible limit is 0.1 (1000ppm). Sources: 1. Expiration of man and animals (at rest man produces ~ 20L/h while animal produces ~ 300 cc CO2 /kg/h). 2. Decay and decomposition of manure and organic matter. 3. Burning of fuel materials (candle liberate ~12 L/h). 4. Underground accumulation. 5. Eructation and bleaching of animals. Over amount is directly removed from air by:- A.Plant exchange.  B. Precipitation by rain ( 2 cc of CO2/L of rain water forming carbonic acid). C. Formation of inorganic compounds as carbonates. Hygienic significance: 1. It is not toxic gas but usually increase on expense of O2. 2. Its presence indicates air pollution. 3. It's increasing over PL, indicate bad or insufficient ventilation, overcrowdings or faults in the drainage system. 4. Overdoses of CO2 may cause:- A.At 50.000ppm---- deep, rapid respiration. B. At 100,000ppm----Violent panting+ narcoting effect. C. At higher than 100.000ppm---Dizziness, unconsciousness. D. At 400.000ppm----struggling, coma, death.  5. In laying hens, higher CO2, increase blood alkalinity due to blood bicarbonates and increasing CO2 tension which is reflected by decrease egg production. 6. Chronic CO2 poisoning may occur in northern farms in winter season (cause?) leading to:- Depressed respiration. Poor aeration of lungs and become more susceptible to diseases. Loss of animal appetite. Lowering productivity. N.B. Determination of CO2 Humidity Definition: is the amount of water vapour in air. Absolute humidity: actual amount of water vapour in the air at prevailing temp.  Relative humidity (RH%): Ratio between Animal spp. B.Wt (kg) absolute humidity and maximum saturation at the same temp. RH%= Absolute humidity X100 Maximum saturation Saturation deficit: Difference between maximum saturation and absolute humidity. SD= maximum saturation-absolute humidity Dew point: Temp. at which water vapour condenses. Sources of humidity inside stable: Expiration of man & animals Calf (birth-12 w) 55-135 Growing cows 180-370 Adult cows 450 Chicken (0-7 w) 0.04-1.25 Layer 1.8-3 Sources of humidity inside stable: 2. Evaporation of liquid manure and urine. 3. Accumulation of wet bedding (in bad ventilated stables). 4. Evaporation of water used in stable cleaning. 5. Evaporation of water from wet feeding stuffs as (bran mashes).  From the previous factors, one should expect that stable air is more humid in summer but the fact that RH increase in winter, why?  PL of RH is 40-70% at 18-22°C. Hygienic significance of RH% 1. It increases the formation of dust. 2. Increase viability of M.Os. 3. Increase No. of insects and disease vectors. 4. Animals are liable to be infected 5. Regulation of body temperature: normally the worm-blooded animals regulate its body temp. through:- A. Evaporation of sweat B. Respiration. C. Conduction.  D. Convection. E. Radiation. F. Urination & Defecation.\ G. Worm blooded animals can regulate their body temp. Within narrow range through a thermal balance between heats produced and heat losses. H. At high temp. and RH%, evaporation of sweat and other sources of heat loss are greatly affected. So there are 4 possibilities:- A. High Temp. and high RH%: 1. Inside the stable: In humid and warm environment- ------Heat loss is greatly impaired------Heat stasis with the following symptoms:- A. Animals become exhausted and debilitated, weak, off food, decrease production. B. Cerebral and pulmonary congestion C. Increase resp. rate. D. High weak pulse rate, dizziness. E. Hear failure. F. Death. 2. Outside the stable: usually occur in working animals. Animals suffer from heat stasis under these circumstances called Sun Stroke. The same symptoms will be appearing on affected animals beside a burning effect on its skin due to the direct sunlight. B- High temperature and low RH%  Excess evaporation of sweat-------rapid respiration----sudden cooling. If the animal is subjected to air current--------resp. affection, joint inflammation and mammary gland inflammation. C- Low temp. and High RH% Chilling diseases as laryngitis, trachitis, enteritis, laminitis, mammary gland inflammation and resp. diseases. D- Low Temp. and Low RH% It is the best condition under which the animal should be housed. The animal health is better, food intake increased and high animal performance. High RH in the poultry houses If RH% increased more than 80%, birds are more likely to suffer from resp. and parasitic infestation due to wetting of the environmental surfaces. From hygienic point of view, high RH is required at fumigation by formaldehyde gas, otherwise the gas will be converted to Para formaldehyde powder. Precautions against high RH (prevention) 1. Well drain soil with low ground water table. 2. Cover internal walls by damp proof layer. 3. Good ventilation. 4. Perfect drainage of liquid and solid manure. 5. Avoid overcrowding.  Air pollution Any substance (Natural or man-made or animal made) present in the air at a concentration high enough above their normal ambient level to produce measurable effect on animal, man or plants. Natural made: volcanic gasses, dust, pollen grains, viruses, fungi or bacteria and so on. Man-made: smoking, industrial plants, motorized traffic, pesticides or radioactive materials. Animal made: ammonia, nitrites odour, faecal matter, animal excreta, etc. Air Impurities I- Solid impurities:- A-Biological B- Dust:- a- Organic b- Inorganic II- Gaseous impurities ( Diffused) A- Group 1 a. Carbon dioxide (CO23) b. Carbon monoxide (CO1) c. Ammonia d. Nitrogen dioxide e. Odorous compounds B- Group2 (Sewer gases) C- Smokes 1. Carbon dioxide (CO2))   Normal level: 0.03%  PL: 0.1%  Its presence indicates:-  A- Bad ventilation  B- high environmental temperature  C. High RH%  So, animals have low body resistance and Low productivity 2. Ammonia (NH3): produced from:-  Decomposition of urine and manure.  Heating of organic matter (coal, oil, etc) in absence of oxygen.  Sources:-  Natural: so little amount.  Industrial: heating of organic matter.  Atmospheric: Hygienic significance:- 1. Its presence indicates, Faulty drainage system; Bad management 2. Its increase inside the houses usually associated with high RH, high temp., poor ventilation, over- crowding. 3. Its harmful effect appears if concentration reaches 0.012% (120 ppm or 1.2mg/L) as reduce body resistance. 4. At high conc., irritates m.ms so increase its liability to be invaded by DPA.  At 40 ppm, day old chicks shows:- 1. Watery eyes ;Closed eye lids; rubbing eyes on wings; Kerato-congunctivitis, Huddling together 2. Decrease growth rate, poor conversion rate. 3. At >80 ppm; resp. diseases. 4. Decrease egg production. 3- Carbon monoxide (CO1) Colurless gas. Combine irreversibly with HB 250 higher than Oxygen to produce carboxy HB. It produces from incomplete combustion of fuel materials. Hygienic significance:- 1. Normally air should free from CO1 2. If reach 0.06% it become harmful. 3. If carboxy-HB:- Reach 20%: animal loss some locomotors control Reach 30%, chemical changes occurs in the body. Reach 60%, animal die. NB: CO1 poisoning is rare in farm animals but usually seen in pet animals with symptoms of hypoxia, in-coordination movement; dyspenia, coma, death (sudden death usually); temporary or permanent deafness in cats, dogs). Carboxy-HB: make the blood bright red and tissues appears as bright pink. Recovery from CO1 poisoning: Oxygen mixed with CO2 (to promote breathing). 4- Sewer gases Includes:- 1. Hydrogen sulphide. 2. Indol 3. Methane 4. Skatol 5. Volatile fatty acids. Compounds of sewer result from faulty drainage system. A-Hydrogen sulphide  Anaerobic decomposition of animal manure, produce H2S.  It is denser than air so usually accumulated at lower levels of air in closed houses.  It has characteristic odour: Rotten eggs.  Hygienic significance: At high conc.; >10 mg/m3 as (conjunctivitis, loss of the appetite; decrease productivity). B- Methane Anaerobic decomposition of animal and/or man, produce methane. It is colorless and odourless, flammable gas. Lighter than air: accumulate near the roof at stagnant corners. Prolonged exposure to methane: generalized tremors, Change blood parameters. Nitrogen Dioxide Fermentation of nitrogenous compounds, produce nitrogen dioxide.  Clinical symptoms of exposure: dyspnea, lacrimation, salivation, low Bl.P.; methhaemoglinaemia. Smoke Burning of organic materials (Coal, wood, gas, oil, etc.), produce smoke (visible or non-visible). Hygienic significance:- 1. Smoky area become undesirable for grazing (annoyance, poor quality plants) 2. Abortion of pregnant animals and poor quality wool (sheep) 3. Calcium deficiency 4. Poultry, decrease egg production. Odorous compounds Aerobic decomposition of animal wastes, produce many odorous compounds. Odour itself may be due to amines, mercaptans, alcohols, acetones, sulphides and ammonia. Hygienic significance: Inhalation leading to tainting of milk, loss of the appetite. II. Solid impurities  Dust:- a. Organic b. Inorganic  Biological  Dust: It represent an important problem in Egypt due to:- 1. Adjacent desert 2. Dryness of the atmosphere. 3. No rain. The concentration of dust depends on the ventilation In-organic dust: As lime salts, iron, silica, sodium chloride, and others (derived from the soil and sea). Hygienic significance: 1. Continues inhalation causing irritation of m.m lining the eyes and upper respiratory tract causing lowering of their resistance to infection. 2. Dust containing lead or arsenic (Insecticides, causing contamination of vegetation and animal poisoning. 3. In poultry: dust usually originates from feed and litter. Its quantity decreased by high RH%. B-Organic dust  Includes all DPA as moulds, fungi, bacteria, viruses, etc.  Sources of microbial pollution of air inside animal stables:- 1. Animal bedding and dust. 2. Animal itself (secretion and excretion. Extent of air pollution depends on:-  3. Indoor environment (microclimatic conditions) as Temp., RH, air velocity, sun rays etc. 4. Animals ( density, species, sex) 5. Management (cleaning, drainage system etc.) 6. Health status of the flock 7. Floating particles of animals, plants and/or man (plant fibers, epithelial cells, feathers, fragments of insects, hairs, manure, pollen grains, and plant cells), are called organic dust. Tracheal cilia can remove all dust greater than 5µ in diameters but smaller than this, find their ways to lower resp. tract. Hygienic significance of organic dust Most of these particles are harmless in nature. Its importance only as a vehicle or carriers of DPA. During spring season, inhalation of floating (huge amounts) pollen grains, inducing a disease in horse (hay fever) or man (spring fever). The disease ch. by catarrhal inflammation. Of upper resp. tract, light fever (39°C). Hygienic significance of biological agents ( Role of air in disease transmission):-  A.Droplet infection: DPA floating in air derived from sneezing, coughing mixed with air Currents. M.Os may be resistant or vegetative Occurs only indoors. Example (pulmonary T.B.; Influenza ; CBPP; Swine plague; Pulmonary Glanders, etc) Infection restricted only to Resp. tract B.Dust infection DPA from any source (Resp. tract, Udder, pus, sputum, milk, uterine Vaginal discharges, urine, faeces, Etc., drops on the ground, dried, floating with air currents, and causing Infection to Resp. or any other system M.Os should resist dryness Occurs usually indoor or outdoor Example: T.B.; anthrax spores, Fungi Moulds; clostridia, etc Effects of polluted air on animal’s health 1. Primary effect on exposed tissues of eye, skin, resp. tract through which gases may be absorbed to blood. 2. Acute or chronic toxicity depending on the conc. Of the pollutant, ventilation rate. 3. Lowered vitality and body resistant against invaders. 4. Reduce animal productivity (milk, meat, eggs, etc.) 5. Weak off springs. 6. Disease occurrence due to M.Os. spreading Air pollution control (Control of air borne infection or prevention of air pollution) 1. Proper spacing of individuals (avoid over-crow dining). 2. Adequate ventilation and lightening. 3. Efficient and periodical disinfection. 4. Apply strict sanitary measures (periodical cleaning, removal of manure, urine, bedding). 5. Periodical microbiological assessment of stable air to apply disinfection. 6. By using air filters specially in the super-intensive houses (spores 0.1µ). Climatic factors and animal health It means average conditions of climate around the animals and includes:- 1. Temperature 2. RH% 3. Rain and snow.  4. Sunshine 5. Wind velocity and direction 6. Clouds. Temperature Farm livestock are homeo-therms. They maintain a balance between heat loss and gain. A- Heat gains: 1-Metabolism 2-Basal heat produced form vital process 3- Digestive heat production 4- Muscular heat production 5- Solar radiation and sunshine B- Heat Loss:- a. Radiation b. Convection c. Conduction d. Evaporation. e. Urine and faeces I. Radiation  Warm body (higher than surrounding) emits heat.  Factors influencing radiation:- a. Body surface area. b. Animal density. c. Difference between body temp. and surrounding. II. Convection  Heat transfer from body to surrounding by air and governed by:- 1. Animal surface area. 2. Temp. difference between body and surrounding 3. Air movement (role heat draught in winter for heat dissipation) III. Conduction Heat loss due to physical contact of animal’s body and surrounding surfaces. Effected by:- 1. Animal surface area. 2. Temp. difference between body and surrounding NB: it is important to cover the floor with a thick layer of bedding during winter. IV. Evaporation Heat loss through water vapour from animal’s skin and lungs. Evaporation from skin depends on:- 1. Temperature 2. RH% 3. Air movement 4. Evaporation from lungs depends on humidity of inspired and expired air. How animal regulate its body temperature Loss of heat or gain in different seasons I. In hot seasons:-  1. Higher breathing to increase Heat loss by evaporation. 2- Evaporation from skin. 3- Increase water intake. 4- Animal avoids sun light. 5-Eat less and reduce movement 6-Physically: as hold wings of chickens on the ground II. In cold seasons: In cold weather animals try to increase heat gain and reduce heat loss through:- 1. Eat more. 2. Depositing more fat under skin to increase insulation. 3. Growing larger and coarser hair. Physically through: Shivering, huddling, etc. Effect of animal surface on body heat regulation Animal’s body plays an important role in the thermoregulatory of body temperature. Heat travels to the body surface by vascular routes and find their ways outside the animal body through radiation, conduction, convection and evaporation. The amount of heat losses depends on:- 1- Skin surface area: there is a direct proportion between body surface and heat lost. 2. Heat difference between animal’s body and surrounding temp. (direct proportion). Heat travel from wormer to cooler surface. 3-Colour of the coat: white coat absorb only 20% of radiation falling on it while black coat absorb 100%. Colour of coat may cause photosensitization, manifested by burns, dermatitis especially in un- pigmented areas of skin 4-Thickness of the coat & hair length: Thick coat and long hair entrap air and moisture and reduce convection loss of heat. It also provide local climate of high humidity and reduce heat evaporation. 1. Effect of temperature Species Comfortable Upper Symptoms zone critical zone Poultry 32-35 °C and 29 °C Reduce gro reduced 3 Brooding (1st °C/week to 16 °C day) on 6th week Reduce egg Reduce qua Layers small sized Comfortable: 16- 21 °C 10-25 °C 1- Effect of Temp. and RH% Exposure of animals to very high temp. and high RH% may cause adversely affect as following:- 1- High Temp. & high RH: adversely affect animal causing heat stasis which clinically appear as dizziness, loss of appetite, death from heart failure and apoplexy (congestion of brain and anaemia in the internal organs  If the animal hardly work under direct sunlight, it may affected by Sun stroke with the same symptoms beside skin burns. 2- High temp. & low RH: excessive sweating. If there is an air current, Muscular pain, resp. affections, Mastitis; chilling diseases. 3- Low temp and high RH%: animal become usually wet, in presence of air current, mastitis, resp. affections, Rheumatic pain, and chilling diseases. 4- Low Tem. & low RH: this is the most suitable environment under which the animal should maintained. Protection against hot environment 1. Supply the animal with cold fresh water. 2. Supply the animal with green fodder. 3. Supply the animal with cold bathing. 4. Supply the animal with shaded shelter. 5. Clipping of animals specially sheep. 6. Avoid hard work in hot days 7. Avoid transportation of animal at mid-day. 8. Affected animals should injected with calcium borogluconate (stimulant)  III- effect of cold weather 9. In cold weather, metabolism is increased. The only bad effect of cold is:- 10. Economically 11. Sudden exposure to cold causing:- 12. Chill diseases:- 13. Contraction of superficial Bl. Vessels 14. Hyperemia in the internal organs 15. Rise of bl. Capillaries pressure, causing rupture of bl.v. causing haemorrhagrs from m.m (resp. tract), blood encourage commensals to cause pulmonary, intestinal and mammary infection. Moreover, W.B.C get decreased and hinder its phagcytic function (reduce body resistance) 16. B- True chill diseases:- 17. Where no pathogenic M.Os: chill causing muscular rheumatism; neuralgia, laminitis, and cramp colic. 18. Sheep can withstand cold while horses are the most animal species affected by it. Protection from cold environment 19. Concentrate feeding 20. Exercise 21. Enough cover and bedding 22. Housing in warm places without draughts. 23. Avoid sudden exposure to cold draughts 24. Air Movement 25. Rate at which air moves over the skin of animals and affect the rate of heat loss (convection). 26. Determination:- 27. Kata thermometer 28. Air manometer. 29. Hygienic significance:- Its effect varies according to ambient temp. and RH%. 30. Air current with higher temp. than body temp., reduce heat loss by convection (heat stasis specially at high RH%). 31. Air current with temp. lower than that of animal’s body, increase convection loss, increase cold stress specially under air draughts. 32. Cold temp., excessive air movement cause chilling diseases. 33. Wind-borne diseases. 34. Poultry: increase mortality rate, reduce growth rate,  III. Solar radiation: It means the radiant energy, which radiates from the sun surface which is:- 1. Part of which goes directly back to the space by scattering from the atmosphere molecules. 2. The remaining part is absorbed and transformed into other form of energy of different wave length. This part is divided into:- a. Heat rays b. Light rays c. Chemical rays Light rays: are visible and are the only ones capable of exciting the sensation of light. When this light is passing through a prism, the prismatic spectrum contains heat, light and chemical rays. The red rays having the longer wavelength and the violet rays of greater wavelength. The greater wavelength beyond the red, known as the infra-red rays and are purely heat rays. The shorter rays beyond the violet of the spectrum, is the ultra- violet rays (U.V.R.) which are chemical in nature. The UVR is capable of ionizing the matter it reaches. Exposure of animals to intense sunlight, causing several disturbances as:- a. Increase heat load, this may affect growth, production and reproduction. b. Cancer eye: as ocular squamous carcinoma in Herford cattle (most susceptible breed). c. Photosensitization: This is a hypersensitivity of the skin. Presence of some feed components in the blood, when acted upon by ultra-violet radiation in transformed into a toxic substances, which harms and may kill the animal. The facial and dorsal skin swells and the nervous system may be included causing paralysis and even death. Effect of colour and skin thickness: Important factors and play important factors of the susceptibility of animals. The unpigmented thin skin is more susceptible to sun burns and photosensitization disorders. Friesian cattle in tropical zones are usually shows skin cancer. Herford breed often suffer from eye epithelioma due to un-pigmented eyelids. Effect of coat colour: The colour of the skin is affecting the amount of solar radiation absorbed. A white hair coat or feathers can reflect most of visible radiation, while blac; coat may absorb up to 100% of the visible radiation. So, a white, yellow with smooth and glossy texture is the best coat for minimize the adverse effects of the solar radiation on cattle. N.B. UVR is useful in the treatment of ringworm. It kills the fungus. Reduction of the effect of solar radiation:- a. Increasing provision of shade in animal buildings. b. Cultivation of trees around. c. Use of refractive over the walls, roofs, with white paints, aluminum or zinc sheets outside.  d. In the hot climate, the animals only graze at early morning or late evening or at night. Heat radiation Heating of the earth and its atmosphere comes from the direct solar radiation (ambient temperature). The heat rays intensify the bactericidal action of the chemical rays. When the heat rays is sufficient in intensity and duration, it themselves become a destructive and inhibitory to the germs life. Chemical rays: The UVR are purely chemical radiant and is a strong disinfectant against microbes. The wavelength between 2800- 2400 Angstrom is the greatest disinfecting agent. Unfortunately, UVR of low penetrating power as it can't pass through the glass, roof sheets, or through the clouds. Some experiments indicate that UVR prevent rickets in the growing chicks and have a marked effect on egg production and hatchability. Light radiation:  Photoperiod: Time between sunrise and sunset. It varies with altitude and season of the year. It is very important for man, animals and plants.  Effect of light:- 1. Promote cleanliness ( sanitation and hygiene) 2. Bactericidal agent specially shorter WL (UVR) by denaturation of microbial proteins + dehydration of microbial cells (thermal effect) 3. Promote oxidation and dryness (enhance cleanliness)  4. Formation of Vit. D under skin Effect of light on puberty and reproduction of animals: I. Light and reproduction of mammalian:- A. Photoperiod and onset of puberty in ewe lambs. B. Photoperiod and reproductive function in cow. C. Photoperiod and rams. Photoperiod and rams:- Photoperiod and rams: Increasing photoperiod responsible for:- 1. Increase libido. 2. Increase semen quality 3. Increase ejaculates volume. 4. Increase sperm motility. 5. Increase No. of normal sperms 6. Increase spermatogenic activity. 7. Increase sperm No./ejaculate Increase fructose conc. (reflect testosterone secretion) which in turn associated with libido. Effect of light on puberty and reproduction of animals: II. Light and avian reproduction A. Effect of light on ovulation B. Photoperiod during rearing. C. Photoperiod during laying. Light and avian reproduction: Spring is a time of increasing photoperiod, stimulate egg production Increase secretion of gonadotrohins Stimulate gonadal function Increasing photoperiod, hasten sexual maturity whereas decreasing photoperiod, delay the onset of lay Light and ovulation: Photoperiod and rearing:  Lighting program for broilers:- 0-3 week, continuous lighting with 1 hr. off in 24h. 3-5 weeks, 3 on and 1 off 5-7 week, 2 on and 2 off 7weeks on ward, 1 on and 3 off Photoperiod during laying: 0-3 day's continuous lighting, 20 minutes/week step-down to reach 6-8 hrs/day at 20 weeks. In laying period, a weekly increase of 20 minutes starting from 20th week age to be at least 14 hrs lighting/day. Lighting program for commercial layers:- 1. 0-1 week, 18 on+6 off 2. 2-18 week, 6 on+ 18 off 3. 19-22weeks, increase light by 45min/week to give stimulus at the begging of laying  4. 23-49 weeks, increase light by 20 minutes/weeks 5. 49 weeks onward, 18 on+6 off Photoperiod and onset of puberty in ewe lambs:  Photoperiod responsible for seasonal differences in the onset of puberty.  Spring born ewe lambs reaches sexual maturity at 5-6 months of age While summer born lambs at 12 months And fall born lambs at 9 months of age Photoperiod and reproductive function in cows: Extremely high temp. environment, summer breeding is un-efficient.  In milder climates as USA, Canada and European countries, breeding efficiency is higher in summer and falls ( days are longer) and lower during short days ( winter and spring). Season of birth also influence age of puberty: Spring born heifers reaches sexual maturity earlier than those born during winter and falls. Long photo- stimulation to gonads.  As bad ventilation and over ventilation has its adverse effect on animal health and productivity, a balance between them should be considered by supplying the animals with fresh air without draughts. This amount could be calculated as hourly cubic air requirements and cubic air space for each animal as following:- Calculation is based on the following facts:- 1. CO2 content in fresh air = 0.03% (0.3 cc/L) 2. Permissible limit in stable air= 0.1% (1 cc/L). 3. CO2 output of animal= 300 cc/hr/kg B.Wt. 4. Average weight of animal= 300 kg (cows) and 450 (buffaloes)  Every liter of fresh air can absorb 0.7cc of CO2 to reach PL.  Air can be changed 3-9 times /hr (5 times in average).  Effective air space= total cubic air space of the building- space occupied by animal  Calculate fresh air requirement for a cow of 350 kg.  CO2 out put= 350x300= 105000cc of CO2/hr.  As each Liter of fresh air can absorb 0.7cc of CO2  So amount of fresh air required to dilute CO2 output to reach PL= 105000/0.7= 15000L= 150m3/ /hr fresh air  As air changed 5 times/hr so fresh required = 150/5= 30m3.  Total cubic air space of the building= effective air space+ space occupied by the animal=30m3+07m3= 30.7m3  The floor area of cow (350kg)= 30.7/3= 10.22 m2 (Height)