Supplementary Readings - 2 | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Temperature and Animal Comfort in Buildings

• Body's Response to Cold:
  • When the environment gets colder, the body initiates mechanisms to conserve heat.
  • These include narrowing of blood vessels, hair or feather erection, and reduced body surface evaporation.
• Critical Temperature:
  • Critical temperature is the point where natural heat conservation is insufficient, and metabolic heat production must increase to maintain normal body temperature.
  • Different species and individuals within a species show variations in critical temperature.
• Factors Influencing Critical Temperature:
  • Natural means like hair, fur, feathers, and subcutaneous fat help retain body heat.
  • Livestock like cattle and sheep have lower critical temperatures, making them more resilient to cold.
  • Well-fed animals can withstand lower temperatures compared to those on a bare maintenance diet.
• Average Critical Temperatures:
  • Critical temperature for pigs ranges from 68°F to 73°F.
  • Cattle with a full coat have a critical temperature below 56°F, while horses have a slightly higher threshold.
  • Dogs, fowls, and other animals also have varying critical temperature ranges.
• Cowshed Temperature and Milk Production:
  • Experiments suggest that maintaining a cowshed temperature around 50°F can be as profitable for milk production as higher temperatures.
  • Ventilating cowsheds efficiently, even at lower temperatures, ensures better air quality and supports cow health.
• Balance Between Temperature and Health:
  • Maintaining cowsheds at lower temperatures can lead to improved health, balancing any potential food waste due to increased metabolic heat production.
  • Linton emphasizes that a temperature of 60°F in cowsheds, though warmer, may result in compromised air quality, affecting cow health.

Temperature Requirements for Livestock

• Optimum Temperatures for Cattle:
  • According to King (1908), ideal temperatures for well-nourished cattle range from 45°F to 50°F.
  • Animals on a maintenance diet prefer a higher temperature, around 56°F to 65°F, as they consume less food, limiting extra metabolic heat.
• Specific Considerations for Dairy Cows:
  • Dairy cows with large udders, covered minimally with hair, may thrive best at temperatures between 50°F and 60°F.
  • Recent studies suggest winter cowshed temperatures as low as 45°F do not significantly affect milk production, with the optimum being around 50°F.
• Consensus on Ventilation and Comfort:
  • Despite slight variations in optimal temperature opinions, experts agree that maintaining environmental warmth should not compromise ventilation.
  • Well-ventilated, cooler buildings for livestock are believed to outweigh potential higher feeding costs due to the improved health and comfort of the animals.
• Temperature in Indoor Piggeries:
  • Indoor piggeries, unlike those suitable for horses and cattle, require different thermal conditions due to pigs' sparse hair covering.
  • Pigs may experience detrimental effects from exposure to cold temperatures, and optimal feeding for fattening pigs is achieved slightly above their critical temperature range of 68°F to 73°F.
• Atmospheric Humidity in Animal Buildings:
  • Standards for humidity in animal buildings vary, but maintaining relative humidity below discomfort levels is crucial.
  • Findlay suggests that if ventilation controls CO₂ below 22 parts per 10,000 and cooling power is under 7 units, humidity is unlikely to cause discomfort or damage to the surroundings.

Ventilation and Its Importance

• Relative Humidity Consideration:
  • Well-ventilated buildings should aim to maintain relative humidity within 5% of the outside air.
  • Striking this balance is crucial for the health and comfort of animals.
• Detrimental Effects of Poor Ventilation:
  • Inadequate ventilation leads to a combination of high environmental temperature and humidity.
  • Extreme cases result in "heat stroke," causing destructive effects on body tissues and potential fatality, often due to heart failure.
  • Prolonged exposure to high temperature and humidity can cause immediate effects like headache and drowsiness in both humans and animals.
• Effects on Adaptability to Climate Changes:
  • Similar to tropical regions, where constant conditions reduce adaptability to sudden climate changes, poorly ventilated buildings hinder livestock's ability to adjust to varying temperatures.
  • Quick transitions from warm, humid interiors to cold outdoor environments pose risks of illness and chilling for animals.
• Risks of Chilling:
  • Swift temperature changes can lead to chilling, increasing susceptibility to diseases like respiratory infections and mastitis.
  • Practices like turning animals out into cold, draughty areas after being in warm quarters should be avoided to prevent chilling.
• Impact on Winter Coat Development:
  • Continuous housing in warm conditions may prevent horses and cattle from developing the protective winter coat they naturally grow when exposed to outdoor elements.
  • Conversely, animals accustomed to outdoor living can lose their protective winter coats when moved to warm indoor environments.

Myths About Warmth and Milk Production

• Common Misconception:
  • Despite scientific evidence, some dairy farmers believe warmth is necessary for milk production.
  • They argue that a sudden drop in temperature can lead to reduced milk yield, especially in the morning after a cold night.
• Root Cause of Reduced Milk Yield:
  • The actual reason is not that cold air hampers milk production but that cows kept excessively warm and in humid conditions are more susceptible to the chilling effect of fresh, cold air.
• Impact on Disease Transmission:
  • Poorly ventilated buildings contribute to the spread of air-borne diseases like tuberculosis, respiratory issues, influenza, foot-and-mouth disease, and swine fever.
  • Inadequate ventilation leads to a higher concentration of infectious material in the air, posing a greater risk of disease transmission.
• Advantages of Well-Ventilated Buildings:
  • Well-ventilated, dry, and cool buildings dilute foul air effectively, reducing its infectious potential.
  • Warm and humid conditions prolong the viability of pathogenic bacteria, increasing their concentration.
• Complex Factors Influencing Productivity:
  • Optimal indoor conditions for maximum productivity involve various factors, including species and breed variation, disease, general management, nutrition, and atmospheric conditions.
  • Scientific evidence indicates that high environmental temperatures can negatively impact productive capacity.

Ventilation Essentials for Animal Buildings

• Purpose of Ventilation: Efficient ventilation in animal buildings serves multiple crucial functions:
  • Removal of excess moisture and warmth.
  • Elimination of suspended and diffused impurities.
  • Provision of a controlled level of air movement.
• Air Exchange:
  • Achieving a balanced air exchange involves bringing in fresh air equal to the volume of foul air removed.
  • This process should occur without causing draught and without significantly lowering the indoor temperature.
• Historical Misconception:
  • In the past, some builders believed that preventing the influx of fresh air would maintain high indoor temperatures in stables or cow-houses.
• Modern Approach:
  • Modern thinking considers animal houses as necessary but aims to make them less conventional ('house-like').
  • The focus shifts towards providing protection from the elements and ensuring ease in feeding and attending to animals.
• Preference for Open-Air Accommodation:
  • Current veterinary opinion encourages a departure from closed buildings.
  • Open-air systems, like open or partially covered yards and paddocks, are favored for various livestock categories, excluding fattening pigs.
• Benefits of Open-Air System:
  • Observations from veterinarians and stockowners support the idea that animals are healthier in open-air systems.
  • Agriculturalists find the open-air approach economically and practically sound.

Floor Space in Animal Houses

• A practical rule for constructing animal houses is to provide floor space between one-fourteenth to one-fifteenth of the total cubic feet of air space.
• For instance, in a cowshed with 800 cubic feet of air space per cow, an effective height of 16 feet results in a floor area of 50 sq. ft. per cow, meeting recommended standards.

Mechanics of Air Flow and Ventilation

• Ventilation involves the continuous exchange of fresh air for foul air, ensuring atmospheric pollution stays within defined standards.
• Ventilation methods can be natural or artificial, with natural methods relying on the physical laws governing air movement.
• The two main natural means for maintaining air purity are the movement of air masses with different temperatures and the diffusion of gases of different densities.

Natural Ventilation

• Natural diffusion of gases, like CO₂ and methane, aids ventilation by preventing their concentration around their source.
• Air passage into and out of a building depends on the movements of air volumes at different temperatures, known as air velocity.
• Similar to wind formation, heated air in a building rises, creating an upward current that needs an outlet for escape.
• Proper ventilation involves placing outlets for warmed air at high points (e.g., the ridge) and inlets for fresh air at low levels to ensure complete air circulation.
• Placing air inlets at low levels, such as just below animals' heads or near the floor, ensures fresh air is readily available for the animals.

Wind as a Ventilating Force

• Wind is a powerful force for ventilation with a two-fold action.
• It drives fresh air into a building through available openings, mixing and diluting the stale air, creating a perforating action.
• Wind also has an aspirating effect, drawing air from various points as it passes, leading to effective ventilation.
• When wind blows across openings, it aspirates air out of the building, setting up currents that bring in fresh air to replace it.
• Even in calm conditions, there is a slow exchange of air, especially if the building's temperature is higher than the outside.

Components of a Ventilation System

• Every ventilation system must include provisions for the escape of foul air and the inlet of fresh air.
• Inlet ventilators come in various forms, including wall windows, direct inlet pipes and boxes, air bricks, and metal gratings.

Types of Inlet Ventilators

• Wall Windows (Hopper Windows):
  • Serve dual purposes of lighting and ventilating.
  • Hopper windows are hinged at the bottom, opening inwards, with guards on the sides to prevent down-draught.
  • Adjustable hopper windows can be partly closed when needed.
• Direct Inlet Pipes and Boxes:
  • Simple and effective for cow byres.
  • Ordinary 4-inch diameter fire-clay drain pipes are used, either level through the wall or at an angle.
  • Common practice in some regions is placing one drain pipe between each pair of cows.
• Air Bricks:
  • Perforated bricks for air admission, available in various designs and sizes.
  • Theoretical inlet area is considered one-third of the brick face area.
  • Some designs give incoming air an upward trend, while others reduce air force as it enters.
• Metal Gratings:
  • Metal gratings flush with the outside wall serve as efficient air inlets.
  • Recess boundaries should be smooth, rendered in cement, and sloped to minimize dust lodgment.
  • Standard sizes of metal gratings range from 12 to 18 sq.in.

Important Consideration

• Some air bricks have holes on the outside smaller than those inside to reduce air force.
• A second grating fitted inside is unnecessary and undesirable as it complicates cleaning.

Inlet Gating with Adjustable Device

An inlet grating with an adjustable or "hit-and-miss" device is available for regulating air flow.

Outlet Ventilators

• Outlet ventilators should ideally be placed at the highest point of the building, like the roof apex.
• Satisfactory outlet ventilation methods include continuous openings in the ridge, adjustable ridge openings, ridge tiles, and louvre ventilators.

Continuous Ridge Opening

• An open ridge, running the full length of the building, facilitates the escape of warmed air with the help of wind passing over the roof ridge.
• This system is suitable for buildings without a loft and is both cost-effective and efficient.
• For byres, a ridge width of 4 to 6 inches is usually sufficient.

Adjustable Ridge Openings (Findlay's System)

• An improvement for exposed buildings involves adjustable ridge openings.
• Glazed sashes along both sides of the ridge, hinged at the lower edge, can be adjusted to regulate the opening width.
• Wind striking on one side creates an aspirating effect, aiding the escape of heated and foul air.
• Roof timbers can be protected with bituminous sheeting, and the system can operate independently on each side.

Roof Lights or Skylights

• Roof lights or skylights, when situated in the middle of the roof slope, are unsatisfactory for ventilation.
• When open, wind blows inwards, causing "cold wind-drops," and without a ridge outlet, it traps warm foul air in the upper part of the roof.

Ridge Tiles

• To provide simple outlet ventilation, every second or third ridge tile can be raised or turned at right angles.
• Effectiveness depends on the absence of boarding that might hinder air escape.
• Specially designed ridge tiles compatible with common roofing materials are available.

Fireclay Ridge Outlets

• Common on old-fashioned and poorly designed new byres and stables.
• Resemble ordinary fireclay T chimney-cans.
• Almost useless due to their small outlet area.

4-inch Drain Pipes for Outlet Ventilation

• An alternative to fireclay ridge outlets.
• Consists of a series of 4-inch drain pipes placed at intervals along the roof apex.
• Provides a simple and efficient means of outlet ventilation.

Louvre-board Ventilators

• Effective air outlet terminal when properly constructed.
• Often condemned due to neglect or improper design and placement.
• Consists of a covered frame or box on the roof ridge filled with sloping boards or metal/glass plates.
• Louvre-boards set at a 50 to 60-degree angle to allow foul air escape and prevent rain ingress.
• Includes a weather fillet to prevent water entry.
• Wind's perflating action passes through the louvred ventilator, creating an aspirating effect.
• Adjustable or movable louvres are discouraged due to neglect and susceptibility to damage.

Outlet Shafts

• Used in lofted buildings.
• Circular shafts are preferable to rectangular ones.
• Constructed with materials like zinc-galvanized or black iron.
• Shaft area should match required air changes.
• Longer shafts have greater extracting power.
• Bends in shafts slow down the air current; if unavoidable, increase the diameter at the bend.
• Avoid unnecessary exposure of shafts to open air in cold weather to maintain extracting power.

Mechanical Ventilation

• Adopted when natural ventilation is inefficient or impractical.
• Two methods: Plenum method - forces air in using fans, and Vacuum method - sucks air out using fans.
• Extraction method found more efficient than the plenum system.
• Commonly used in mines and ships carrying livestock.
• Essential in ventilating ship holds with livestock to remove foul air and bring in fresh air.
• In ships, electrically-driven intake and exhaust fans are placed at opposite ends of the hold.
• No fixed rule for fan size; analysis of the air current circuit is needed for each case.
• System may fail if doors or openings are left near the exhaust fan.
• Well-designed mechanical ventilation is highly efficient and works excellently in various applications like cattle sheds and poultry houses.

Investigating Atmosphere in Animal Buildings

• Assessing the efficiency of ventilation requires observations during average weather conditions after the building has been occupied for some time.
• Initial signs of indoor atmospheric conditions include animal odors, temperature differences from outdoors, and a sense of humidity or freshness.
• Excessive indoor humidity may lead to condensation on walls, windows, and metal surfaces, indicating ventilation issues.

Measuring Indoor Environmental Conditions

• Ventilation's main role is to remove excessive warmth from the area occupied by animals or people.
• Four factors need consideration: air temperature, humidity, air movement rate, and radiation from surroundings.

Methods for Measuring Factors

• Air Temperature:
  • Commonly measured with a mercury-in-glass thermometer.
  • For recording extreme temperature changes, use a maximum and minimum thermometer placed away from animal exhalations and direct air flow.
• Atmospheric Humidity:
  • Best measured with a whirling hygrometer.
  • Observe wet-and-dry-bulb temperatures to read humidity from tables.
  • Dry-bulb thermometer indicates air temperature, and the wet-bulb registers below it unless air is saturated with water vapor.
  • Increasing temperature difference between dry and wet bulbs suggests lower air humidity.
• Air Movement Rate:
  • Measures the speed of air flow in the building.
  • Various instruments and methods can be employed for this purpose.
• Radiation from Surroundings:
  • Considers the heat emitted by surfaces.
  • Measured using suitable instruments.

Whirling Hygrometer

• Accuracy Improvement:
  • The whirling hygrometer is considered more accurate than other types for measuring humidity, especially in stagnant air.
  • This instrument ensures accurate results by rapidly moving air over thermometer bulbs.
• Instrument Description:
  • Consists of two thermometers in a frame with a handle.
  • The handle allows the thermometers to be rapidly rotated, ensuring the bulbs pass through the air at a high speed.
  • One thermometer's bulb is covered with thin muslin, kept wet by a wick leading to a water reservoir.
• Usage and Reading:
  • Before observation, ensure the muslin covering the wet bulb is thoroughly wet.
  • Whirl the instrument rapidly for about 30 seconds, then stop and immediately read the wet-bulb temperature.
  • Repeat the process until two consecutive readings of the wet-bulb temperature closely match, indicating the minimum temperature.
  • Record both wet-bulb and dry-bulb temperatures.
• Reading Sequence Importance:
  • It's crucial to read the wet-bulb temperature first after whirling stops to avoid temperature rise.
• Relative Humidity Calculation:
  • Relative humidity is determined using paychrometric tables based on the difference between wet-and-dry-bulb temperatures at a given air temperature.

Measuring Air Velocity: Kata Thermometer

• Air Velocity Measurement:
  • Various instruments are used to measure air movement speed in different situations.
  • For assessing environmental warmth in rooms or buildings, the kata thermometer is a convenient tool.
• Kata Thermometer Overview:
  • Devised by Sir Leonard Hill to measure air's cooling power, indicating body heat loss.
  • Original form: Alcohol thermometer with a large polished glass bulb (colored red) and graduations at 95°F and 100°F.
  • Improved type: High-temperature silvered kata thermometer with graduations at 125°F and 130°F or 145°F and 150°F.
• Calculating Air Velocity:
  • Observations of heat loss help calculate the 'cooling power' of the air.
  • Using cooling power and air temperature, air velocity can be determined.
• Current Use:
  • Kata thermometer is now primarily used for measuring air velocities.
  • Beneficial for ventilation issues in animal buildings, such as cattle sheds.
• Observation Points:
  • To assess air movement accurately, observations should be taken at different locations and levels.
  • Useful for identifying stagnant air pockets or draughty areas, especially near the floor and at the animal's body level.
• Application in Animal Buildings:
  • Helps in detecting issues like draughts affecting recumbent cows' udders.
  • Findlay (1948) suggested a dry kata cooling power of 7 as indicative of good ventilation.