By: Tanka Khanal, Ph.D., DVM,
Monogastric Nutritionist
Grand Valley Fortifiers
This article serves as a follow-up to the previous one titled “Undergrade eggs: consider your nutrition-Part I”, which was published in the Spring 2024 edition of our Poultry Grist. A rise in undergrade eggs during and after peak production is one of the major challenges for egg producers, causing significant economic loss. The rejects and cracks contribute to a major proportion of the “undergrades.” Part I highlighted nutritional intervention through limestone particle size distribution and vitamin D3. In this article, I will discuss other possible intervention tools to reduce undergrade eggs.
Balancing Available Phosphorous
While eggshell formation does not require phosphorous, a significant amount of calcium (Ca) is needed, and Ca and phosphorus metabolism are closely linked. Eggshell mineralization (formation) mostly occurs overnight when the light is turned off and hens are in a fasting state. The extra calcium required in this active state of eggshell formation is contributed by bone. On an average, one egg (59 g) requires 2.2 to 2.3 g of calcium to form 5.8 g of eggshell. If sufficient Ca is not coming from feed, calcium phosphate in labile bone will release Ca to form the eggshell. Lower phosphorous in the diet will inadequately replenish the calcium phosphate in the bone. With the continuous release of bone calcium in a long lay cycle, there will be less calcium available for eggshell overall, eventually resulting in thinner and weaker eggshells.
Higher phosphorus in the diet will affect the calcium absorption and is also a potent inhibitor of calcium carbonate mineralization of eggshell. Recent research suggests that excess phosphorous through inorganic phosphate sources has detrimental effects on bone and mineral metabolism, which eventually affects eggshell formation, leading to poor eggshell strength. So, balancing available phosphorous based on type of available ingredients is considered to reduce undergrade eggs.
Controlling Egg Size
Most producers like larger eggs because this category has a premium associated with it. What about the extra-large eggs? It does not have any additional premium on top of large eggs. But, if we carefully analyse grade out data throughout the laying period, we could see a very strong positive correlation (data not presented here) between cracks and proportion of extralarge eggs. Also, we will see a strong negative correlation between medium and extra-large egg percentage. Now the question is: what is the breakeven point for maximizing net return when considering the percentage of cracks, extra-large, and medium? Ensuring the egg size specifically for medium eggs is less than 10% but not less than 6% and extralarge plus large eggs not less than 86% showed better return.This principle works well especially for the eggs laid after 45 weeks of age or post-peak lay. A nutritionist should carefully take body weight, breed type (egg size is influenced by bird types), metabolizable energy, and amino acids into consideration. A proactive control of egg size could be a strategy to reduce “undergrades.”
Controlling Acidosis in Hens
A lot of stress and a lot of metabolically active cellular process of prolific laying hens generates a large amount of hydrogen ions (H+) and other acidic ions on daily basis. The present day hens are metabolically active all day, every day. The enormous rate of ATP (energy) utilization generates a lot of H+.
The net acid production increases during protein oxidation, bone formation, and ATP utilization. Imbalance of amino acid ratios and insufficient protein in the diet could lead to a massive protein oxidation. Oxidation of sulphur containing amino acids (e.g. Methionine and Cysteine) lead to higher levels of acidosis due to formation of sulphate and H+ ions. Diets containing more meat meal, fish meal, or feather meal contain excess acid forming elements. The chloride ions from some additives (for example lysine HCl, choline Chloride etc) and common salt (NaCl) also contribute to acidosis. Dietary electrolyte balance is another highly important aspect a nutritionist should investigate to control acidosis. Replacing some common salt with sodium bicarbonate and modifying the dietary electrolyte balance through formula modification could be an approach to reduced acidosis. Also, choice of ingredients which do not release massive amount of H+ ion during metabolism could potentially reduce acidosis. Preventing acidosis in laying hens is important to reduce ”undergrades”.
Understanding Dietary Fibre Source
Normal hulled barley consists of around 21.8% dietary fibre, of which 12% is soluble fibre. Considering the total dietary fibre, barley has around 55% the soluble dietary fibre. If we analyse in this way, of the total dietary fibre, corn and wheat has around 10% and 50% soluble fibre respectively. These soluble fibres make the feces viscous, soft, and pasty. There is a significant positive relationship between a higher proportion of dietary soluble fibres and incidence of dirty eggs. A dirty egg is the single most important factor leading to rejection of eggs at graders. Better understanding the dietary fibre types and source will contribute to a reduction in the number of dirty eggs.
Pullet Rearing and Frame-Size
Average daily feed intake is a key strategy to control egg size with the provision of sufficient nutrients. This will eventually prevent increased egg crack percentage after 45 weeks of age, when hens start eating more than 114 g of feed daily. To achieve this, it is important to maintain the uniformity and body weight of hens. This starts with the uniformity of the pullet. Hence, better body weight and uniformity remain key players to egg size and “undergrades”. So, an excellent pullet nutrition program will provide a better body weight, strong frame-size by 10 weeks of age, as well as the optimum frame size and lean to fat ratio by 16 weeks of age.
Conclusion
Reviewing dietary available phosphorous could help to deposit more calcium in bone, which later can be used to make eggshell. Controlling acidosis through dietary electrolyte balance can help reducing egg cracks. Understanding dietary fibre sources and their impact on feces texture and use of specific enzymes could significantly reduce dirty eggs, hence less undergrade eggs. Better uniformity and frame size at the pullet phase can improve later life eggshell quality and result in less cracks.
This article was written for the Fall/Winter 2024 Poultry Grist. To read the whole Poultry Grist, click the button below.