Identity

Late-stage production feeding phase for commercial egg-type layers.

Overview

Layer Phase II is a high-priority feeding phase implemented during the latter portion of a layer bird's production cycle. During this phase, the hen’s rate of egg production gradually declines, the average egg size typically increases, and the efficiency of intestinal calcium transport and renal reabsorption diminishes with age. To address larger egg sizes requiring more shell material, the standard raises the minimum calcium requirement while reducing available phosphorus to prevent physiological antagonism. Crude protein is also reduced to control egg size expansion and maintain shell thickness.

Structured Facts

Classification

Feeding Phase > Layer; Layer Feeds > Late-Cycle Laying Rations.

Biological Functions

Extends shell stability, supports late laying phase performance, maintains eggshell quality, and manages late-cycle egg size expansion.

Nutritional Requirements

Raised minimum calcium requirement (4.0%) and reduced available phosphorus (0.33%). Reduced crude protein (13.0%).

Deficiency

• Clinical Signs: Thinner, more fragile shells.
• Economic Impact: Late-cycle egg breakage.

Toxicity

• Clinical Signs: Excess circulating phosphorus acts as a physiological antagonist to calcium absorption and inhibits calcium deposition on the eggshell membrane.

Interactions

Excess circulating phosphorus antagonizes calcium absorption in the gut.

Feed Phase Requirements

• Pre-Starter: Not applicable
• Starter: Not applicable
• Grower: Not applicable
• Finisher: Not applicable
• Breeder: Not applicable
• Layer: Weeks 46 to 72+.

Quantitative Data

• Requirement: Metabolizable Energy, Crude Protein, Calcium, Phosphorus, Lysine, Methionine, Threonine.
• Minimum Level: Metabolizable Energy: 2400 kcal/kg; Crude Protein: 13.0%; Calcium: 4.0%; Total Phosphorus: 0.65%; Available Phosphorus: 0.33%; Lysine: 0.70%; Methionine: 0.30%; Methionine + Cystine: 0.52%; Threonine: 0.52%.
• Maximum Level: Moisture: 11.0%; Crude Fibre: 10.0%; Acid Insoluble Ash: 4.5%; Salt: 0.5%.
• Unit: Percentage (%) by mass (dry matter basis), kcal/kg.

Relationships

• Related Nutrients: Calcium, Phosphorus, Lysine, Methionine, Threonine.
• Breeds: Egg-Type Layers.
• Production Stages: Weeks 46 to 72+.