NUTRITION ▶▶▶
Supporting eggshell quality and the economics of egg production
An integrated feed, farm and health strategy, including tailored supplementation strategies, farm feeding practices and health management can support eggshell quality, the longevity of layers’ productivity and producer economics.
BY ROLAND KOEDIJK AND ALICE HIBBERT, TROUW NUTRITION H
igh-quality eggshells are a prerequisite for first- grade eggs and production economics. But achiev- ing good eggshell quality becomes more difficult during the late stages of a layer’s production
when hens’ shells become thinner while their eggs become larger. This challenge can prompt farmers to replace aging layers with younger hens, compromising economics and environmental sustainability.
Feed and farm factors Good eggshell formation requires critical macro minerals and essential trace minerals supplied in the feed. Calcium in feed is absorbed into the hen’s bloodstream where it is deposited in medullary bone or used directly by the bird. As a calcium reservoir, medullary bone is a buffer between hens’ calcium uptake in the day and calcium deposition around the eggshell at night. Older hens metabolize calcium in feed less efficiently than younger birds, leading to thinner eggshells. Several studies have shown that increasing calcium in older hens’ diets can support eggshell integrity and reduce the number of broken eggs. Studies also show that time of day matters when it comes to hens’ utilization of nutrients. Researchers observed that when birds were freely able to select dietary intake, hens
Table 1 – Trace mineral recommendations for optimum egg production.
Overall
Copper Zinc
Manganese Iron
Iodine Selenium 48
15 60 80 25 1
0.3 Late lay
(eggshell challenge) 15
100 120 40 1
0.3 ▶ POULTRY WORLD | No. 10, 2021
under-consumed calcium in the morning and consumed much more of it in the afternoon. These intake patterns re- flect physiological processes in the bird required for egg pro- duction. Research suggests a split-feeding strategy in which birds receive one-third of their calcium in the morning and the remaining two-thirds in the afternoon feed can optimise hens’ calcium intake. While most of an egg’s phosphorous is not found in the shell ultrastructure, phosphorus intake has a major influence on calcium metabolism. High levels of bloodborne phosphorus inhibit calcium mobilization from bone. A meta-analysis found that dietary non-phytate phosphorous (NPP) could be decreased to meet laying hens’ requirements and maintain health and productivity at lower than recommended levels of supplementation. The typical recommendation to feed 350 to 450 mg NPP per hen per day is nearly twice the required level informed by research. Bioavailability is another factor to consider. The inclusion of a nutrient in a premix does not guarantee that it will be absorbed into the hen’s system. For example, phytase – an enzyme used in 90% of poultry feed – can degrade phytate. Phytic acid levels will define the possible phosphorous re- lease and the potential for interaction with other ingredients in the feed. Trace minerals are a good example of ingredients that can interact with phytate. Trace mineral sources with lower solubility, such as hydroxy copper, zinc and manganese, remain intact in feed and prevent soluble trace mineral ions from releasing and inhibiting the efficacy of phytase.
Absorption and availability Although small fractions of the hen’s overall diet, zinc, man- ganese and copper must be supplemented because raw ma- terials in feed don’t supply adequate levels of these essential nutrients required for eggshell formation. Zinc is required to activate carbonic anhydrase, essential for the deposition of calcium carbonate and the basis for a strong eggshell. Research has shown that supplementing hens’ diets with zinc reduces defects, such as soft, broken or deformed shells. Manganese helps increase the degree of effective thickness and total thickness of eggshells. Copper synthesizes collagen for egg production. Mineral source stability and solubility explain the wide var- iation between how trace minerals interact with other feed ingredients and influence oxidation reactions in the bird. The availability of the mineral following intake and the bird’s abil- ity to metabolize the mineral are both affected by the mineral
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