Eggs, a fundamental product in human diets worldwide, provide a convenient and essential source of nutrients for people everywhere. They are one of the most affordable sources of animal protein and are often hailed as nature’s complete food. Remarkably rich in high-quality amino acids, eggs boast a wealth of near-pure protein content.
Egg consumption is on the rise globally due to greater recognition of its nutritional benefits. Per capita egg consumption in the European Union is projected to grow by 0.7% from 2019-2030. The EU accounted for 11.2% of world egg production in 2021, while Asia held the leading position as the world’s largest producer with 61.1% of world production.
With its unique structural properties, the eggshell offers a natural and convenient packaging for the transport of an egg’s contents. However, from a biological standpoint, the avian eggshell design primarily serves to safeguard the chick embryo during its development. This protective function commences with the cuticle, a protective layer that envelops the outer surface of the shell.
Similarly, the egg-white antimicrobial peptides are specifically designed to ensure the safety and well-being of the developing embryo. These properties extend their protective benefits to those who consume the eggs. The nutrition, age of the flock, health and microbiological status of the hens, along with egg collection, handling, washing and packaging, directly impact both the external (eggshell) and internal egg properties influencing the risk of egg contamination and potential foodborne outbreaks for consumers.
Trace mineral nutrition represents an opportunity to enhance eggshell quality during the entire production cycle, particularly as the hen ages. Achieving this goal necessitates understanding how trace minerals influence the long-term health of the hen and the organs involved in egg production, as well as recognising the significance of minerals at various stages of the egg formation process.
Like a well-constructed building meant to withstand the test of time, the eggshell comprises ‘bricks’ (calcium carbonate) and ‘cement’ (organic matrix). Zinc (Zn) plays a crucial role as a key supplier of carbonate (bricks), while the organic matrix is created through the finely regulated interaction of zinc (Zn), copper (Cu) and manganese (Mn). This process results in the formation of glycosaminoglycans, collagen fibres and the cross-linking (cement) found in eggshell membranes, as well as the proteins in the calcified eggshell matrix. Therefore, Zn, Cu and Mn are the 3 most crucial trace minerals in developing a resilient egg structure.
Zinc from ZPM boosts eggshell quality by enhancing carbonic anhydrase activity in the plasma and eggshell gland of aged layers, resulting in +14.5% and +7.7% carbonic anhydrase activity in the plasma and eggshell gland tissue, respectively, of 67-week-old hens. This Zn-dependent enzyme is important for eggshell calcification as it catalyses the hydration of CO2 to HCO3(carbonate) which is then pumped into the lumen of the shell gland along with calcium ions.
Furthermore, manganese from ZPM improved the antioxidant response of hens at both younger and older stages of egg production, showing +58% superoxide dismutase activity in the plasma of hens at 46 weeks of age and +21% superoxide dismutase activity in the shell gland of hens at 92 weeks.
Zinpro Mn supported the expression of genes encoded for proteoglycan, glycoproteins and calcium binding proteins in the shell gland of 66-week-old hens. Increasing the expression of such genes leads to greater mammillary knob density during the initial stages of eggshell formation, thus improving eggshell quality.
In a notable study, 45-week-old Hy-Line Brown layers that were fed Zinpro Mn (40 mg Mn/kg feed) for 25 weeks demonstrated the highest egg production with an increase of +2.1%, compared to hens fed 40 mg Mn/kg of feed in the form of Mn sulphate. These eggs displayed an enhanced organic matrix content in both the membrane and calcified eggshell, resulting in an improved eggshell ultrastructure and greater breaking strength (as depicted in the table below).
Egg breakage has long been an economic burden for the egg industry, accounting for approximately 8% of total egg production that requires downgrading. As hens age, this percentage can escalate significantly. However, investing in zinc and manganese can lead to a substantial reduction in cracked eggs, thereby increasing the number of saleable eggs.
Feeding ZPM trace minerals to commercial Hisex White layers proved to be highly beneficial. This resulted in an improvement in egg resistance to breakage, with increases of +6.2%, +3.1% and +4.1% as hens aged from 76 to 80 and 88 weeks, respectively. Additionally, the incidence of broken eggs declined, showing a remarkable 73% reduction.
Under research conditions providing ZPM to White Leghorn hens from 73 to 85 weeks yielded improvements in eggshell quality. The study showed a reduction of 6.1% in the incidence of cracked eggs when hens were supplemented with 40 ppm Zn and 40 ppm Mn ZPM instead of 60 ppm Zn and 70 ppm Mn from oxide forms. Furthermore, when hens were fed 40 ppm Zn and 40 ppm Mn from ZPM, along with 20 ppm Zn and 30 ppm Mn from oxide forms, there was a significant 9% drop in cracked eggs.
With the increasing demand for egg consumption and the layer industry moving towards higher welfare standards, maintaining high performance becomes critical to a successful operation. The goal to deliver stronger hens and higher quality eggs can be achieved through the use of Zinpro Performance Minerals, as they have been proven to address the major factors that can impact layer health and productivity. By integrating these advanced mineral supplements into their nutrition programme, poultry producers can enhance overall performance and meet the evolving demands of the market and consumers.
References available on request.