Egg Size

Maintaining egg size in the large category is important to both egg producers and nutritionists, as this is the best way to maximize profitability over the life of a layer flock. Canadian egg farmers are paid for their eggs based on the size of egg they produce. The egg sizes are categorized as: pee-wee (less than 42 grams), small (42 to 48 grams), medium (49 to 55 grams), large (56 to 63 grams), extra-large (64 to 69 grams), and jumbo (more than 69 grams).

Profitability
Because the price paid for large and extra-large eggs is higher than the other categories, an egg producer’s best strategy to maximize profitability is to reach large egg size quickly and then stay in that category. While there are many factors known to affect egg size, nutrition can play a significant role in controlling egg size, both in the pullet and layer barn. Because nutritionists understand the need for large eggs, they pay close attention to the nutrients that have major impacts on egg size to ensure they are adequate to support the production of large eggs.

Pullet Nutrition and Management
A good pullet is the base for a good layer. Consequently, nutritionists focus on creating feeds that support the development of a good pullet. The nutrition and management provided during the pullet phases have long-lasting effects on egg size, and subsequent profitability, in the layer barn. The key to pullet nutrition is to ensure the nutrients being provided are supplied in adequate amounts to support the pullet’s ability to reach target body weights. This is important because pullets that are on or slightly above the target weights will be the best producing birds as there is a proven relationship between the body weight of the pullet at sexual maturity and egg size. The focus for pullet nutrition during the first fourteen weeks is on body frame development. Nutritionists focus on providing adequate levels of protein, fat, and calcium in order to support the development of the skeletal system, while still allowing for muscle growth and maintenance. By fourteen weeks of age, approximately 90 per cent of the body frame size is developed and at this point, the size of the pullet is essentially fixed. Beyond fourteen weeks of age, the nutritional focus of the pullet is turned towards supporting sexual maturity and preparing for the start of lay by providing calcium to build up calcium reserves for egg laying. During this time, nutritionists are making sure the feed is providing adequate protein and fat levels to support the rapid growth of the reproductive system, but also ensuring the fat levels are not so high that the pullet becomes obese. Managing the feed to ensure the pullets are receiving adequate protein levels to create a solid frame, as well as supporting their nutritional needs throughout the development of their reproductive system, is the key focus for pullet nutrition.

Feed Intake of the Laying Hen
Increased feed intake in the layer barn will typically encourage egg size, while decreased feed intake will lead to a smaller egg size as body reserves will be used as an energy source instead of contributing to egg formation. Monitoring feed intake is necessary to understand how much energy and protein the hens are consuming, as this impacts nutrition and management decisions.

Protein and Amino Acid Intake
Protein and amino acids are the major nutrients that influence egg size and subsequent profitability. Approximately 50 per cent of the dry matter of an egg is protein and each egg is created with the same amino acid composition, which highlights the importance of supplying amino acids to the laying hen for protein synthesis. When it comes to protein and amino acids, nutritionists are focused on providing balanced amino acids to the hens to make sure they have the amino acids they need to lay an egg every day. A diet that is unbalanced in terms of amino acids will cause a reduction in egg size or stop egg production because a hen is simply not able to produce an unbalanced egg. Protein intake is also very important because it is directly related to egg size. Egg size can be encouraged by increasing the protein level in the feed and can be manipulated by decreasing the protein level in the feed. Overfeeding protein will result in the egg size increasing too quickly and will increase feed costs, while potentially decreasing egg numbers. On the other hand, underfeeding protein will result in a drop in production. Nutritionists ensure a range of diets are available for the producers to feed to their hens during the lay cycle, with the understanding that changing the protein level of the diet is the best way to either encourage or control the egg size of the hens. It is important that producers understand the impact of dietary protein and amino acid levels on egg size so they are able to choose the correct protein levels for their birds to achieve maximum profitability throughout the lay cycle. The easiest way to ensure the correct protein level is being provided to the hens is to weigh your eggs once per week from the same place at the same time. For example, weigh six flats of eggs twenty minutes into egg packing every Wednesday. This will allow you to compare your egg weight at a given age to the breed targets and ensure you are managing egg size to maximize profits in your operation.

FAT AND LINOLEIC ACID INTAKE
Egg size is dictated by the size of the yolk and is greatly influence by the body weight of the hen. The yolk is primarily made up of fat, which is why fat intake is very important for laying hens. Linoleic acid is also of particular importance because it is required in order for the developing yolk to take up increased fat levels. Nutritionists pay close attention to the fat and linoleic acid being provided to the hen during production and make sure that these levels are adequate to support the production of a large egg and maximize profits for the producer.

CONCLUSIONS
Egg size is a very important factor to consider and track in a layer flock because of the large impact is has on the producer’s profitability. It can be manipulated through many different factors, including pullet nutrition and management, as well as feed, protein, and fat intake in the layer barn. It is important to understand that while it is possible to manipulate egg size to a certain extent, the genetic potential of the bird will dictate how far egg size can be pushed. Nutritionists, working closely with the producer, must have a good understanding of how nutrition and management impact egg size and manipulate it to their advantage to control the egg size when it is too light or too heavy. This working relationship will help an egg producer maximize their profitability and achieve the optimum number of large eggs.