Canadian Poultry Magazine

Nutrition Perspective: Reducing undergrade eggs

By Tanka Khanal   

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There are several critical control points where producers can work to reduce undergrade eggs. In this article, Tanka Khanal from Grand Valley Fortifiers shares a few key considerations.

Cracks contribute to a large proportion of egg undergrades. Photo: Grand Valley Fortifiers

Egg consumption per capita has increased by more than 30 per cent over the last decade (2012 to 2022) in Canada. If we look at 2022, more than 1,200 registered egg producers in this country produced on an average more than 2.32 million dozen eggs daily.

Egg production in Canada has been consistently increasing since 2005. It increased by 1.1 per cent for the year 2021 compared to 2020. Table eggs (approx. 70 per cent) and processed eggs (approx. 30 per cent) are two major categories of the Canadian egg market.

Having many undergrade eggs is one of the Canadian egg industry’s major problems. Usually, undergrade eggs cross two per cent.


It is alarming when undergrade eggs crosses 2.5 per cent of the total grade out.

The undergrade eggs include cracks, class B, and rejects. The actual undergrade is even higher because farmers grade out some cracked and rejected eggs, mostly blood-tinged at farm level before sending to the graders.

There are several critical control points where we can work to reduce undergrade eggs. For instances, case structure, nest position (for enriched cage), lights (duration, intensity and colour), egg belt and wire, belt run time, egg handling, trucking and transportation, and graders etc. However, in this article I take a nutritional point of view.

Egg grade out in Canadian context
Graders in Canada categorize eggs into nine different grades. They include jumbo, extra-large, large, medium, small, peewee, class B, cracks, and rejects. Class B, cracked, and rejected eggs. These cumulate to give total undergrades.

Cracks contribute to a major proportion of undergrades mostly ranging from 40 to 60 per cent, followed by rejects and then class B. The cracks and rejects contribute more than 80 per cent of total undergrades. Therefore, the focus of this discussion is on how to control crack and rejected eggs through nutrition.

Nutrition plays a significant role in controlling cracks and reject eggs. This article discusses two aspects of controlling cracks and rejects: primary and secondary. Thus, the article is split into two sections.

The first section discusses calcium utilization by hens for eggshell quality and, thus, eventually lower undergrades. This means understanding and applying the concepts of limestone particle size distribution, its impact on fractional passage rate of calcium from gizzard to duodenum, calcium digestion and absorption, and vitamin D3 activity on active calcium utilization.

The second part will discuss on enhancing available phosphorous, controlling body weight gain during lay, preventing acidosis in hens, rearing pullets to optimum frame size and bone health for less undergrades. Additionally, implementing split feeding from the beginning of peak lay could give a better eggshell quality and fewer undergrades at least-cost formulation.

Enhancing calcium utilization
In general, the limestone particle size is maintained through the specified ratio of fine to coarse limestone. A nutritionist should also focus on distribution pattern of limestone particle size in the given limestone type.

Determining the limestone particle size distribution and adjusting the ratio of fine to coarse accordingly could give a better ratio of larger to fine limestone. This will affect the fractional passage rate of calcium from gizzard to duodenal loop and will significantly affect the calcium utilization from intestine to uterus during active eggshell formation process in the night.

This will affect eggshell thickness, breaking strength and eventually crack percentage. The calcium utilization is of paramount importance, as influenced by limestone particle size distribution and activity of Vitamin D3.

Vitamin D3 and late lay
Vitamin D3 is an essential nutrient to optimize calcium (directly) and phosphorous (indirectly) utilization in laying hens. Vitamin D3 improves apparent retention of calcium. Poor eggshell and eventually higher undergrades because of larger proportion of cracks in the late lay phase is a common problem in Canadian and global egg industry.

Sometimes, several laying hens, especially during peak and egg lay in closed housing, face leg problems and show a temporary abnormal gait. Adding extra vitamin D3 (regular or activated) could enhance performance, fix the temporary abnormal gait, and enhance eggshell thickness and breaking strength.

Now, an important question is, “How much of vitamin D3 or activated vitamin D3 (25 hydroxycholecalciferol, 25OHD3) is required to get a better result when there is incidence of poor eggshell quality?” The answer depends on the level of vitamin D3 in basal diets.

If vitamin D3 level in basal diet is less than 4,000 IU/Kg of ration, supplementing extra 5,000 IU/kg (125 µg/kg) of vitamin D3 or activated vitamin D3 for a short period (1.5 to two weeks) improves performance, eggshell quality, and cracks. Modern day hens could produce more than 93 per cent of eggs even after 68 weeks of age. 

And at that age, eggs are usually bigger. Thus, supplementing extra vitamin D3 at regular intervals could enhance performance and eggshell quality.

Canadians’ per capita consumption of eggs has been increasing for a decade and still shows sign of continuing to increase. Persistent lay with better grades is one of challenges of our egg industry. A nutritionist plays a vital role in controlling poor gradings.

When considering calcium for eggshell quality and undergrade eggs, a nutritionist should look at the distribution of limestone particle size too rather than just only from the ratio of coarse to fine limestone in formulation. Determining limestone particle size distribution and adjusting the ratio of fine to coarse accordingly could give a better supply of calcium for eggshell formation.

Better utilization of calcium through vitamin D3 fortification could provide better eggshells and help prevent structural bone mineral loss. 

This could prevent quick bone drainage and poor eggshell quality at late lay. Supplementing extra 5,000 IU/kg (125 µg/kg) of vitamin D3 or activated vitamin D3 for a short period at regular intervals could be a practical application to improve performance and reduce undergrades. 

Tanka Khanal is a poultry nutritionist and graduate degrees holder from Wageningen University & Research, the Netherlands (MSc) and University of Guelph (PhD). He is a principal poultry nutritionist at Grand Valley Fortifiers. Contact him at

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