Unit3 - Subjective Questions

Definition: Incubation is the management of a fertilized egg to ensure the satisfactory development of the embryo inside into a normal chick. It involves maintaining specific conditions of temperature, humidity, and turning.

Incubation Periods:

To ensure high hatchability and healthy chicks, the following criteria should be considered when selecting hatching eggs:

• Fertility: Eggs must be fertile, sourced from healthy breeder flocks with proper male-to-female ratios.
• Egg Size: Medium-sized eggs are preferred. Very large or very small eggs have lower hatchability.
• Shape: Eggs should have a standard oval shape. Misshapen eggs often do not hatch well.
• Shell Quality: The shell should be smooth, strong, and free from cracks. Eggs with thin shells, ridges, or excessive porosity should be rejected.
• Cleanliness: Eggs should be clean. Dirty eggs can introduce bacteria; however, washing hatching eggs is generally discouraged unless done with specific sanitizers.
• Age of Egg: Hatchability declines as the storage period increases. Ideally, eggs should be set within 7 days of laying.

Successful artificial incubation depends on four primary physical factors:

1. Temperature: This is the most critical factor. The optimum temperature for forced-draft incubators is usually (). Fluctuations can lead to early embryonic death or weak chicks.
2. Humidity: Relative Humidity (RH) prevents the egg from losing too much moisture.
   • Setter phase: RH.
   • Hatcher phase: RH to soften the shell membranes.
3. Ventilation: The developing embryo requires Oxygen () and expels Carbon Dioxide (). The incubator must provide fresh air containing and ensure levels do not exceed .
4. Turning: Eggs must be turned to prevent the embryo from sticking to the shell membrane. In automatic systems, eggs are turned through a angle every hour.

Definition: Candling is the process of examining an egg in front of a strong light source in a dark room to observe the internal development of the embryo.

Schedule:

• First Candling (5th–7th day): To identify fertile and infertile (clear) eggs.
• Second Candling (18th day): To separate living embryos from dead-in-shell embryos before transferring eggs to the hatcher.

Objectives:

1. To remove infertile eggs to save incubator space.
2. To remove dead embryos which might rot and explode (exploders), contaminating other eggs.
3. To analyze flock fertility and storage problems.

Natural Brooding:

• Relies on a broody hen to provide warmth and protection to the chicks.
• Capacity: Limited to 15–20 chicks per hen.
• Suitability: Only suitable for small-scale or backyard poultry keeping.
• Cost: Low cost, no equipment needed.

Artificial Brooding:

• Utilizes a mechanical device (brooder) to provide artificial heat.
• Capacity: Can handle large numbers (hundreds or thousands) of chicks.
• Suitability: Essential for commercial farming.
• Control: Allows precise control over temperature and sanitation, reducing disease transmission compared to the hen method.

Proper temperature management is crucial for thermoregulation in chicks, as they cannot regulate their body heat initially.

• Starting Temperature: The temperature under the hover (brooder) should be () for the first week.
• Weekly Reduction: The temperature should be reduced by () every week until it reaches the ambient room temperature (approx or ).

Schedule:

• Week 1:
• Week 2:
• Week 3:
• Week 4:

Chick Behavior: If chicks huddle near the heat source, it is too cold. If they move far away and pant, it is too hot. Even distribution indicates comfort.

Hatchery hygiene is vital to prevent diseases like Omphalitis and Aspergillosis.

Sanitation Steps:

1. Cleaning: Thorough physical cleaning of incubators, trays, and floors to remove debris.
2. Disinfection: Washing with disinfectants.

Fumigation:
Fumigation involves using Formaldehyde gas to kill microbes. It is usually done using Formalin and Potassium Permanganate ().

Standard Concentration ():

• For every $100$ cubic feet of incubator space:
  • Formalin: $40$ ml
  • : $20$ g
• Procedure: Place in a container and pour Formalin over it. Gas is released instantly. The room/incubator is closed for 20-30 minutes.
• Precautions: Formaldehyde is toxic to humans; use masks and ensure ventilation after the process.

Definition: Debeaking, or beak trimming, is the removal of part of the upper and lower beak of a bird using an electrically heated blade (cauterization) to prevent regrowth and bleeding.

Recommended Age:

• Ideally done at 1 day old (hatchery) or within 1–2 weeks of age.
• Sometimes repeated (touch-up) before laying (16 weeks) if necessary.

Advantages:

1. Prevents Cannibalism: Reduces injuries from pecking, toe pecking, and vent pecking.
2. Reduces Feed Wastage: Prevents birds from selectively picking feed and flicking it out of the trough.
3. Reduces Egg Eating: Prevents layers from breaking and eating their own eggs.
4. Uniformity: Helps maintain flock uniformity by reducing bullying.

Concept: Restricted feeding is the practice of limiting the amount or nutrient density of feed provided to growing pullets (usually between 8 to 20 weeks) rather than providing ad libitum (free choice) feed.

Methods:

1. Quantitative: Limiting the daily feed allowance.
2. Qualitative: Feeding low-energy or low-protein diets.
3. Skip-a-day: Feeding on alternate days.

Importance/Advantages:

1. Delays Sexual Maturity: Prevents pullets from laying eggs too early (precocious maturity).
2. Increases Egg Size: By delaying onset, the initial eggs laid are larger.
3. Reduces Obesity: Prevents accumulation of abdominal fat, which can cause prolapse during laying.
4. Reduces Feed Cost: Lowers the cost of rearing pullets.
5. Improves Livability: Generally results in healthier, more productive layers.

Cage System (Battery Cages):

• Space: High stocking density; requires less floor area per bird.
• Hygiene: Birds do not come in contact with droppings; lower risk of Coccidiosis and worms.
• Feed Efficiency: Higher, as movement is restricted.
• Egg Quality: Cleaner eggs, easier collection.
• Disadvantages: High initial capital, welfare concerns (restricted movement), problem of cage layer fatigue.

Deep Litter System:

• Space: Birds kept on floor with bedding (litter); requires more space ( sq. ft per bird).
• Welfare: Birds can express natural behaviors (scratching, dust bathing).
• Vitamins: Birds synthesize Vitamin from the litter.
• Disadvantages: Higher risk of parasitic diseases (Coccidiosis), dirty eggs, higher labor for litter management, lower feed efficiency due to movement.

Role of Lighting:
Light stimulates the anterior pituitary gland via the optic nerve and hypothalamus to release Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). These hormones are responsible for the development of the ovary and the release of the ovum (yolk).

Key Principles:

• Growers: Light duration should never increase during the growing period (to prevent early maturity).
• Layers: Light duration should never decrease during the laying period (to prevent cessation of lay).

Standard Program:

1. Rearing: Natural daylight or decreasing light is used.
2. Stimulation: At 18–20 weeks (approx. 5% production), light is increased.
3. Production: The total photoperiod (Natural + Artificial) should be maintained at 16 to 17 hours per day. Artificial light is added to natural daylight to achieve this constant duration.

Definition: Cannibalism is a vice where birds peck at the toes, vents, feathers, or bodies of other birds.

Causes:

1. Overcrowding: Lack of floor space or feeder/waterer space.
2. Nutritional Deficiencies: Salt (Sodium) deficiency, protein deficiency, or lack of fiber.
3. Lighting: Excessive light intensity or prolonged duration.
4. Temperature: High temperatures causing stress.
5. Parasites: External parasites causing irritation.

Control Measures:

1. Debeaking: The most effective preventive method.
2. Management: Provide adequate space ( sq.ft for broilers, $2.0$ sq.ft for deep litter layers).
3. Nutrition: Ensure balanced diet, specifically salt and amino acids (Methionine).
4. Lighting: Reduce light intensity or use red bulbs.
5. Isolation: Immediately remove injured birds to prevent others from learning the vice.

Definition: Culling is the identification and removal of unproductive, sick, or undesirable birds from the flock to save feed costs and prevent disease spread.

Distinction (Good vs. Poor Layer):

Definition: A brooder guard is a barrier, usually made of cardboard, hardboard, or GI sheets, placed around the brooder (heat source) in a circle.

Purpose:

1. Confines Chicks: Keeps chicks near the heat source so they do not stray away and get chilled.
2. Prevents Crowding: The circular shape prevents chicks from piling up in corners (which leads to suffocation).
3. Draft Protection: Shield chicks from cold floor drafts.

Arrangement:

• Height: Usually 12 to 18 inches high.
• Distance: Placed 2 to 3 feet away from the edge of the brooder hover initially.
• Expansion: The circle is expanded gradually as chicks grow and is typically removed after 7–10 days during summer or 15 days in winter.

Hatchability is influenced by genetic, physiological, and environmental factors:

1. Fertility: Without fertilization, there is no hatchability. Influenced by male-to-female ratio and age of breeders.
2. Genetic Factors: Inbreeding reduces hatchability; crossbreeding often improves it (heterosis). Lethal genes can cause embryonic death.
3. Nutrition of Breeders: Deficiencies in vitamins (Riboflavin, Vit , Vit ) and minerals (Manganese, Calcium) reduce hatchability.
4. Egg Storage: Storage beyond 7 days reduces hatchability. Improper temperature () or humidity during storage harms the embryo.
5. Incubation Conditions: Deviations in temperature, humidity, ventilation, or turning.
6. Egg Characteristics: Very large/small eggs or poor shell quality decrease hatch rates.
7. Disease: Vertical transmission of diseases (e.g., Salmonellosis, Mycoplasmosis).

Definition: Phase feeding is a feeding program that divides the laying cycle into different phases and provides a specific diet for each phase, tailored to the changing nutritional requirements of the bird.

Objective: To optimize egg production, egg size, and shell quality while minimizing feed costs and nutrient wastage.

Phases (Example):

1. Phase I (Onset to Peak, approx. 18–40 weeks): High protein (18-19%) and high nutrient density to support body growth and rapidly increasing egg production.
2. Phase II (Post-Peak, approx. 40–60 weeks): Protein is slightly reduced (16-17%) as body growth stops, but Calcium is maintained/increased for shell quality.
3. Phase III (Late Lay, 60+ weeks): Protein is further reduced (15-16%), but Calcium is significantly increased () to prevent thin shells and egg breakage in older birds.

Definition: Physiological zero is the temperature threshold below which embryonic development ceases and above which cell division (development) restarts. For poultry eggs, this is approximately ().

Significance:

1. Storage: Hatching eggs must be stored below this temperature (ideally or ) to keep the embryo in a state of suspended animation (dormancy) until incubation starts.
2. Prevention of Weak Embryos: If storage temperature fluctuates above physiological zero, the embryo starts developing and then stops again when cooled. This start-stop process weakens the embryo and leads to high early embryonic mortality during incubation.

Adequate spacing is vital to prevent stress and maintain production.

1. Floor Space:

• Light Breeds (e.g., Leghorns): $1.5$ to $2.0$ sq. ft per bird.
• Heavy Breeds (e.g., Rhode Island Red): $2.5$ to $3.0$ sq. ft per bird.

2. Feeder Space (Linear):

• Growers: $3$ to $4$ inches per bird.
• Layers: $4$ to $5$ inches per bird (approx. 10-12 cm).

3. Waterer Space (Linear):

• Growers: $0.75$ to $1.0$ inch per bird.
• Layers: $1.0$ to $1.5$ inches per bird (approx. 2.5 cm).

Note: In circular feeders/waterers, the circumference is calculated, and space requirements per bird are generally reduced by 30-40% compared to linear troughs.

Sexing is the process of separating male and female chicks, usually done at day-old in hatcheries.

Importance:

• Layers: Only females are required; males are culled.
• Broilers: Sometimes separated to rear sexes separately for uniform growth.

Methods:

1. Vent Sexing (Japanese Method): Examining the rudimentary copulatory organ in the cloaca. Requires high skill.
2. Auto-sexing (Color Sexing): Uses sex-linked genes where males and females have different down colors (e.g., Silver/Gold gene).
3. Feather Sexing: Uses slow/rapid feathering genes. Females usually have primary wing feathers longer than coverts at hatching, while in males, they are of equal length.
4. Instrumental Sexing: Using a proctoscope (less common now).

Definition: FCR is a measure of an animal's efficiency in converting feed mass into the desired output (eggs).

Formula for Layers:
There are two common ways to calculate FCR for layers:

1. FCR per Dozen Eggs:
   

2. FCR per kg Egg Mass (More precise):
   

Example:
If a hen eats $110$ g of feed to produce a $60$ g egg:

Economic Importance:

• Feed constitutes 65-70% of production costs.
• A lower FCR indicates better efficiency (less feed needed for the same output).
• Monitoring FCR helps in evaluating feed quality, health status, and overall profitability.