Feeding Lower Levels of Chelated Minerals vs. Industry Levels of Inorganic Trace Minerals on Broiler Performance

Trace minerals are required to ensure the health and productivity of livestock species. However, requirements are poorly defined in most species and our understanding of the relationship between mineral source and its ability to meet specific requirements lacks precision. As a consequence inorganic trace minerals (ITM) are included in poultry diets at levels several times NRC [3] recommendations. Low absorption coupled with high inclusion results in high levels of trace minerals in the litter. When this litter is used as fertilizer these minerals contribute to soil excess and offer potential for environmental insult [2].

Research has documented that mineral bioavailability varies considerably between sources. Wedekind and Baker [4] showed Zn from the oxide was only 0.44 as available as that from the sulphate. More recently interest has been directed from ITM sources to minerals which are bound, often a chelate structure, to an organic ligand resulting in trace minerals with greater bioavailability. A number of studies in which accumulation of trace minerals in key tissues as tibial bone have shown the availability of these chelated trace minerals (CTM) to be between 110% and 180% when compared to the most available inorganic salt [1]. Use of these chelated sources allows nutritionists to reduce the trace mineral content of the feed while still meeting the animal requirements. In the current trial trace mineral inclusion were significantly reduced via Zn, Cu and Mn chelated to the hydroxy analogue of methionine (MINTREX®). Broiler performance was compared vs diets containing current USA levels as inorganic salts under commercial production conditions. 

Two 54d grow-out trials were conducted in a commercial broiler facility to determine the impact on performance, yield, foot pad lesions, and litter trace minerals concentration by feeding broiler chicks diets containing lower levels of supplemental Zn as MINTREX® Zn [Zn(HMTBa)₂] (Trial 1) or MINTREX® Zn, MINTREX® Mn [Mn(HMTBa)₂] and MINTREX® Cu [Cu(HMTBa)₂](Trial 2) in comparison to industry levels of inclusion of respective inorganic trace minerals (ITM). A total of 122,400 Ross-708 straight-run chicks were distributed into 8 identical production houses with about 15,300 chicks/house for Trials 1 and 2. Both trials had 2 treatments (T1 and T2) each with 4 replicate houses per treatment.

Trial 1. The treatments were: 30ppm Zn as MINTREX® (T1) and 100ppm Zn as ZnSO4 (T2). Trial 1 was carried out on a year old piled up litter.

Trial 2. The treatments were: 32/8/32 Zn/Cu/Mn (ppm) as MINTREX® (T1) and 100/125/90 Zn/Cu/Mn (ppm) as sulphates (T2). Trial 2 was on fresh litter.

Corn/soybean diets were formulated to meet requirements at all stages of growth and fed in four phases (Starter Day 0 to Day 14; Grower Day 15 to Day 35; Finisher 1 Day 36 to Day 45; Finisher 2 Day 46 to Day 54). The diets were balanced for methionine content to take account of the methionine activity in the CTM source. Management of the birds was carried out under standard procedures for the commercial facility. Two hundred birds per house were weighed on Days 7, 14, 35 and 45 and overall performance was determined on Day 54 when foot pads were scored on a 5 point scale. On Day 53, 16 birds per house (8 males and 8 females) were sacrificed for analysis of tibia bone strength and Zn content. On days 55 and 56 two composite litter samples were taken from each house and analysed for trace mineral content.

Data subjected to pair wise (t test) comparison. Foot pad data were subjected to chi-square test. 

Both Trials 1 and 2 results indicate no differences (P>0.05) in performance, carcass yield, and tibia Zn over 54d period between treatments.

Trial 1. On d 54, the chicks fed diets supplemented with MINTREX® had 27.3% more grade 1 and 2 paws together compared to that of T2 (P<0.01). Feeding 30ppm supplemental Zn (Mintrex Zn) compared to 100ppm of Zn as ZnSO4 resulted in:

• Similar (P>0.05) performance and carcass yield,
• Numerically improved body weight by 18g,
• Significant (P<0.001) improvement in paw scores, and
• Similar tibia breaking strength and tibia Zn.

Trial 2. Broiler performance over 54 days is summarized below:

There were no significant differences between the performance parameters measured. Tibia zinc was also the same in both groups (ITM: 80.08 mg/kg; MINTREX® 80.74 mg/kg; P=0.52).

Evaluation of foot pad health using a 5 point scale showed a significant improvement in birds fed the chelated mineral diet. The combined percentage of feet in the top categories 1 and 2 for the chelate group was 40.0% whereas for the ITM group this was 24.5% (P=0.0001).

Use of chelated minerals at lower rates of inclusion in the diet had a significant effect on litter trace mineral content (P<0.001). These data are shown in Fig. 1.

Fig. 1. Impact of use of chelated mineral source on litter mineral content (mg/kgDM)

 

The development of chelated mineral sources with a higher bioavailability in the animal provides the opportunity to lower inclusion rates in the diet while maintaining animal performance. In this experiment the inclusion rates of Zn, Cu and Mn as chelates were reduced to below NRC [3] recommendations without having an effect on broiler growth rate or feed conversion ratio when compared to US industry standards. An interesting effect of chelate use was the improvement in foot pad health reflecting the importance of all three trace minerals in the maintenance of skin and connective tissue structure. In view of the link between foot pad health and animal welfare this observation has particular relevance in modern broiler production systems.

The reduction in trace mineral inclusion rate also had a significant effect on litter mineral content providing an opportunity to reduce the environmental impact of commercial poultry operations. 

The supplemental ITMs were effectively replaced with reduced levels of MINTREX® without compromising bird performance, yield, tibia breaking strength, and bone and tissue mineral concentration. Feeding reduced levels of MINTREX® resulted in a significant improvement in foot pad health and reduction in litter trace minerals concentration. 

1. Ao T, Pierce JL, Power R, Dawson KA, Pescatore AJ, Cantor AH, Ford MJ. Evaluation of Bioplex Zn® as an organic zinc source for chicks. International Journal of Poultry Science. 2006; 5: 808-811.

2. Nicholson FA, Chambers BJ. Livestock manure management and treatment: implications for heavy metal inputs to agricultural soils. In: Trace elements in animal production systems. 2008; pp 55- 62. Wageningen Academic Publishers, eds P. Schlegel, S. Durosoy and A.W. Jongbloed.

3. NRC. Nutrient Requirements of Poultry, 9th revised edition. 1994; NAS-NRC, Washington, D.C.

4. Wedekind KJ, Baker DH. Zinc bioavailability in feed-grade sources of zinc. Journal of Animal Nutrition. 1990; 68: 684-689.