Describe different factors which influence the voluntary feed intake in poultry.

Voluntary feed intake in poultry is a multifactorial trait influenced by a wide range of factors. These can broadly be categorized into environmental, dietary, physiological/genetic, and management-related aspects.

Environmental Factors

The external conditions surrounding the birds significantly impact their willingness and ability to consume feed.

• Ambient Temperature: This is arguably the most critical environmental factor.
  • Heat Stress: Poultry are homeothermic and reduce feed intake in hot environments to minimize metabolic heat production from digestion, which contributes to their body temperature. Feed intake can decrease by approximately 1.5% per °C rise above 21°C. This reduction can negatively impact growth and egg production. Water intake, conversely, increases significantly during heat stress (2-fold at 32°C, 2.5-fold at 37°C compared to 21°C) to aid evaporative cooling.
  • Cold Stress: In colder temperatures (below the thermoneutral zone, typically 18-24°C for adult birds), birds increase their feed intake to generate more body heat and meet higher maintenance energy requirements to maintain core body temperature.
• Humidity: High humidity, especially when combined with high temperatures, exacerbates heat stress, making evaporative cooling less effective and further reducing feed intake.
• Lighting Program:
  • Duration: Daylength influences feeding opportunities. Longer light periods generally allow for more feeding time, potentially increasing intake.
  • Intensity: High light intensity can increase bird activity levels, leading to higher maintenance energy requirements and potentially increased feed allocation. Adequate light intensity (e.g., sufficient during the first 7-10 days for chicks) stimulates activity, encouraging feed and water consumption.
• Ventilation: Proper ventilation is crucial for maintaining optimal environmental conditions, removing heat, ammonia, and other noxious gases. Poor ventilation can lead to heat stress and reduced air quality, depressing feed intake.
• Stocking Density: High stocking density can lead to increased competition for feed and water, elevated stress levels, increased ambient temperature, and higher ammonia levels, all of which can negatively impact individual bird feed intake and uniformity.

Dietary Factors

The composition, physical form, and quality of the feed directly influence its palatability and how much birds will consume.

• Nutrient Density (Energy and Protein):
  • Poultry generally eat to satisfy their energy requirements. Diets low in energy may stimulate higher feed intake to compensate, while high-energy diets reduce it.
  • However, feed intake can also be influenced by the level of the first limiting nutrient (e.g., protein, essential amino acids), rather than solely by energy content. Deficiencies or excesses of specific nutrients can disrupt this regulation.
• Feed Form and Particle Size:
  • Pellets vs. Mash/Crumble: Pelleted feed generally promotes higher feed intake and better feed conversion ratios compared to mash or crumble because it is easier and quicker to consume, reducing energy expended on eating.
  • Fines: High levels of fine particles in pelleted feed can reduce palatability, increase sorting behavior, and decrease feed intake, leading to poorer performance.
  • Particle Size Uniformity: Consistent particle size in mash diets is important for uniform nutrient intake and preventing selective feeding.
• Palatability and Anti-nutritional Factors:
  • Ingredients with poor palatability (e.g., certain raw legumes with anti-nutritional factors like trypsin inhibitors) can significantly reduce feed intake.
  • Presence of mycotoxins or other contaminants in feed can severely depress appetite, lead to illness, and reduce feed intake.
• Water Availability and Quality: Water intake is highly correlated with feed intake. Any restriction in water access, poor water quality, or unsuitable water temperature will drastically reduce feed consumption.

Physiological and Genetic Factors

Intrinsic characteristics of the bird play a significant role in determining its feed intake capacity.

• Age and Physiological Stage:
  • Young Birds: Chicks and young, rapidly growing broilers have high metabolic rates and, consequently, high feed intake relative to their body size to support rapid growth.
  • Layers: Pullets gradually increase feed intake as they approach peak egg production to meet the high energy and nutrient demands of egg formation. Older layers may experience declining intake.
  • Breeders: Feed intake in broiler breeders is often restricted to manage body weight and optimize reproductive performance.
• Breed and Genetic Strain: Different genetic strains and breeds have varying growth rates, production potentials, metabolic rates, and efficiencies of nutrient utilization, leading to inherent differences in their voluntary feed intake. Modern broiler breeds are selected for rapid growth and high feed intake.
• Body Weight and Composition: Heavier birds generally have higher maintenance energy requirements and thus higher feed intake. Body composition (lean vs. fat tissue) also affects energy requirements.
• Health Status and Stress:
  • Disease: Any illness, infection, or parasitic infestation can significantly depress appetite and reduce feed intake.
  • Stressors: Physical stressors (e.g., handling, vaccination, transportation) and immunological challenges can lead to a reduction in feed intake.

Management Factors

Farm management practices directly influence the environment and accessibility of feed and water.

• Feeder Space and Design: Insufficient feeder space or poorly designed feeders can restrict access, leading to competition and reduced overall feed intake, especially for less assertive birds.
• Feed Delivery System: The frequency and uniformity of feed delivery are crucial. Ensuring that feeders are never completely empty or overfilled, and that feed is evenly distributed, encourages consistent intake.
• Brooding Management: Correct brooding temperature, easy access to feed and water, and proper light intensity in the early days are vital for establishing good initial feed intake, which sets the stage for future performance.
• Disease Control and Biosecurity: Effective biosecurity measures and prompt disease management are essential to prevent health issues that can severely depress feed intake.
• Waterer Management: Adequate waterer space, proper height, and cleanliness are as important as feeder management, given the strong correlation between water and feed intake.

The interplay of these factors is complex, and a holistic approach is necessary to optimize voluntary feed intake in poultry for efficient and profitable production.