Trace minerals play specific roles in avian metabolism, all of which are relevant to the laying hen (Table 1). Their role becomes apparent when diets deficient in these micro nutrients are fed to high-performing laying hens.

The OTM that most improves the tissue supply of the key trace minerals zinc, copper and manganese has the greatest direct effect on connective tissue and bone development, in addition to improving immune response in poultry. Studies in broilers (Richards et al., 2007; Manangi et al., 2012a; Yuan et al., 2011) have shown improvements in intestinal breaking strength, foot pad quality and bone strength when HMTBa chelates are included in the diet. Recent research with layers provides further evidence that inclusion of HMTBa chelates of zinc, copper and manganese improves bird health and performance

Bone Strength

One study (Manangi et al., 2012b) was conducted a laying cycle using four treatments: (1) a control, (2 and 3) zinc, copper and manganese ITMs at 100% or 50% of commercial levels and (4) HMTBa chelates at 50% of commercial inclusion. In addition to production parameters, tibia bone strength was measured at 80 weeks. The results are shown in Figure 1. The ITMs provided little benefit over the control. The tibia breaking strength of HMTBa chelates was 9% greater than with the control and 6% greater at the 50% commercial inclusion rate.

Immune response

As a consequence of its role in the activation of key enzymes, zinc status has a direct effect on immune function in the bird, and the source of the mineral influences this process. In a challenge study (Richards et al., 2005), broilers showed an enhanced immune response following coccidial challenge when the dietary zinc source was zinc-HMTBa versus a control, zinc sulfate and zinc methionine treatments (Figure 2).

Oxidative stress

Oxidative damage to the tissues is regulated by a number of systems, including the activity of the enzyme superoxide dismutase, which is sensitive to tissue trace mineral supply. In an experiment in which broiler diets were supplemented with zinc, copper and manganese as either ITM, HMTBa chelate or other OTM, the plasma concentration of peroxide, a breakdown product of tissue lipid damage, was measured. Peroxide concentration, an indicator of oxidative stress, was significantly lower in the birds supplied with the HMTBa chelate (Figure 3).

Eggshell production

In terms of eggshell production, the role(s) of the three key trace minerals are summarized in Figure 4. Formation and calcification of the collagen matrix is dependent on enzymes that require trace minerals as essential co-factors. For example, manganese deficient layers have a lower shell mass and more shell defects due to low activity of glycosyl transferase, which is essential for proteoglycan synthesis. Similarly, the enzyme carbonic anhydrase is zinc dependent and essential for calcium deposition to form shell structure. Egg production decreases in zinc deficient birds.

Eggshell strength

The use of OTMs in layer diets is designed to improve the supply of key trace minerals to the tissues of the bird in order to enhance both productivity and health. In an early field study with layer breeders, eggshell strength was investigated during a 45-week period with two diets: one containing ITMs at 100 parts per million each of zinc, copper and manganese and a test diet with HMTBa chelates at 50 ppm of zinc, 10 ppm of copper and 65 ppm of manganese. The effect of the HMTBa chelate treatment on eggshell strength during the period of lay from 35 to 80 weeks is shown in Figure 5. Eggshell strength, measured in Newtons, was consistently higher (P < 0.05), with 3.6% stronger eggs in the HMTBa chelate group during the experimental period, which resulted in more salable eggs.

Egg production

In a second experiment (Manangi et al., 2012b), use of the HMTBa chelate sources of zinc, copper and manganese resulted in improved bird performance when compared to both an equivalent level of ITMs (40 ppm of zinc, 10 ppm of copper and 40 ppm of manganese) and the commercial level (80 ppm of zinc, 20 ppm of copper and 80 ppm manganese), demonstrating the value of using a highly available source of these key trace minerals in layer diets.Fig 6:

Eggshell thickness

Further analysis of eggshell structure showed a consistent increase in eggshell thickness in the birds fed the HMTBa chelated minerals. This effect on eggshell quality was confirmed in a field study where, during a nine-week period (weeks 72-81 of lay), substituting 50% of the ITMs in the diet with HMTBa chelated minerals resulted in a 3.2% reduction in cracked eggs and a 2% reduction in broken eggs (Figure 7).

Egg freshness

In the same study, eggs were sampled at 52 weeks of age. A total of 15 eggs per treatment were stored at room temperature for 10 days. Then, freshness was assessed by measuring albumen height and was expressed as Haugh units. Supplement at ion with HMTBa chelates significantly increased (P < 0.05) Haugh units after 10 days in storage (Figure 8).

Conclusion

HMTBa chelates improve the tissue supply of the trace minerals zinc, copper and manganese and have a direct effect on connective tissue and bone development, in addition to improving immune response in poultry. In laying hens, this affects bird health, eggshell strength and egg quality factors, which are critical to performance under current production conditions. Therefore, HMTBa chelates can provide additional support when the period of lay is extended. HMTBa chelated trace minerals allow nutritionists to reduce the inclusion rates of trace minerals while meeting the requirements of the bird.