Summary

The objective of this study was to investigate the impact of long-term inclusion of the trace elements zinc, copper, and manganese chelated with the hydroxy analogue of methionine on layer performance, eggshell quality, tibia breaking strength, and immune response.

A total of 216 Hy-Line W-36 laying hens were allocated to 6 treatments with 36 pens/treatment and 1 hen/cage using a randomised complete block design.

There were 6 treatments with supplemental Zn-Cu-Mn, as follows:

• T1 0-0-0 ppm,
• T2 20-5-20 ppm as sulfates,
• T3 20-5-20 ppm as chelates,
• T4 40-10-40 ppm as sulfates,
• T5 40-10-40 ppm as chelates,
• and T6 80-10-80 as sulfates.

The feeding of dietary treatments started at week 24 pullet age and measurements of the key parameters were made from week 44 to 80.

Overall results (one-way ANOVA) indicated a significant treatment effect (P < 0.05) for shell thickness (at week 74).

Hens fed either no supplemental trace minerals (T1) or lower levels of supplemental inorganic trace minerals (ITM) (T2) had lower (P < 0.05) shell thickness when compared to high levels of sulfates (T6).

Supplemental minerals as chelates at lower levels (T3) resulted in comparable (P > 0.05) response to T1 and T6 but different (P < 0.05) from T2.

Factorial analysis of the data showed an improvement in shell breaking strength (P < 0.05 at week 68), shell thickness (P = 0.08 at week 68; P = 0.03 at week 74), tibia breaking strength (P = 0.07) and antibody (Ab) titres to SRBCs (P < 0.05 at week 63; 1 week after secondary antigen challenge) in hens fed chelated trace mineral when compared to inorganic trace minerals.

In summary, feeding laying hens’ diets containing supplemental chelated trace minerals showed improvements in eggshell thickness and immune response when compared to inorganic salts at specific time points measured during the latter part of the laying cycle.

Key words: Zn, Cu, Mn, layers, chelates.

Description of Problem

Eggshell quality is a key aspect of successful egg production, broken and cracked eggs representing a significant loss to the industry and to the individual producer. These effects become even more significant as hens age.

In addition, in highly productive birds demineralisation of the structural bone can result in increased osteoporosis and bone fractures. Again these effects are particularly prevalent towards the end of lay.

In addition to the requirements for the macro minerals, calcium and phosphorus, and Vitamin D3 it is well-recognised that there are key trace elements which are essential for shell and bone formation.

In particular zinc (Zn), copper (Cu), and manganese (Mn) have specific roles in the pathways of shell formation. The impact of deficiencies in these trace minerals has been documented by a number of authors.

For Zn these include decreased egg production and eggshell quality linked to its role as a cofactor in the enzyme carbonic anhydrase, which is essential for shell deposition.

Manganese-deficient hens are reported to produce eggs with thinner shells with an alteration in the structure of the organic matrix reflecting the role of the mineral in the synthesis of chondroitin sulfate. Addition of Mn to the diet of hens in the second cycle of production improved eggshell thickness.

Copper is a cofactor in the enzyme lysyl oxidase which catalyses the crosslinking of collagen and elastin, and a deficiency results in eggshell deformities.

The provision of trace elements in the diet has been traditionally achieved through the use of inorganic salts of the minerals, i.e., inorganic trace minerals (ITM).

These are the sulfate or oxide salts of the mineral and, commercially, are often included in the diets in excess of the levels recommended by national bodies such as the NRC. This reflects the uncertainty in the availability of mineral elements from ITM sources and the desire to ensure an adequate supply to the tissues of the bird.

By their very nature, however, these minerals are only required in trace amounts by the tissues of the body and dietary minerals in excess of these requirements are excreted in the litter contributing to environmental pollution.

Concerns over this process are resulting in pressure to reduce the dietary content of specific trace minerals (for example, Zn) focusing attention on the use of more bioavailable sources of these key nutrients.

Mineral ions from ITM are known to interact with dietary components forming insoluble complexes which reduce mineral availability.

By contrast minerals chelated to organic ligands, i.e., chelated trace minerals (CTM), have been shown to have a greater bioavailability. For example, Richards et al. showed that the bioavailability of chelated Zn is between 160 and 250 per cent that of inorganic Zn as sulfate.

These data suggest that there is a potential to meet the requirements of the bird at lower inclusion rates in the diet.

Results from trials with both breeders and layers in which organic trace minerals (OTM) have been used have shown a range of responses. Inclusion of Zn and Mn improved performance and eggshell quality in some whereas there was no positive impact of OTM use in others.

The objective of the current study was to investigate the long-term effects of the use of a CTM source of Zn, Mn, and Cu compared to ITM sources in layers on performance, eggshell quality, tibia breaking strength, and immune response.

Reference: M. K. Manangi, M. Vazques-Anon, J. D. Richards, S. Carter, and C. D. Knight (2015) 'The impact of feeding supplemental chelated trace minerals on shell quality, tibia breaking strength, and immune response in laying hens'. J. Appl. Poult. Res. 24:316–326.