Over supplementation of inorganic trace minerals is common practice in the poultry industry which often results in poor bioavailability and low body retention. This can lead to more than 90% of the dietary trace minerals being excreted. The trace minerals Cu, Mn and Zn have been shown to contribute to a healthy skin through their roles in the structural proteins of collagen, keratin and elastin. In this study the effects of replacing industry levels of inorganic Cu, Mn and Zn with lower levels of 2-hydroxy- 4-(methylthio) butanoic acid (HMTBA)2metal chelates of Cu, Mn and Zn was investigated on broiler performance, carcass characteristics, skin and intestinal integrity and the prevalence of foot pad dermatitis.
Two 35-day grow out trials were conducted in an environmentally controlled broiler facility. The purpose of the first trial was to find a litter moisture level to be applied in a subsequent trial in order to simulate most commercial conditions where the prevalence of foot pad dermatitis is relatively high. In Trial 2 a total of 1920 Ross first grade day-old male broiler chicks were randomly distributed into 32 identical concrete floor pens. The dietary treatments in Trial 2 consisted of:
Inorganic treatment (standard commercial trace mineral levels) containing 10, 100 and 100 mg/kg Cu, Mn and Zn, respectively (from inorganic sulphates)
Negative control containing reduced inclusion levels of inorganic Cu, Mn and Zn at 8, 32 and 32 mg/kg, respectively (from inorganic sulphates)
(HMTBA)2 chelated Cu, Mn and Zn at inclusion levels of 8, 32 and 32 mg/kg (from only Mintrex® Zn, Mintrex® Cu and Mintrex® Mn, respectively)
(HMTBA)2 chelated Cu,Mn and Zn at inclusion levels of 30, 32 and 32 mg/kg (from only Mintrex® Zn, Mintrex® Cu and Mintrex® Mn, respectively).
Broiler performance results of body weight (BW), body weight gain (BWG), feed intake, mortality, and feed conversion ratio (FCR) adjusted for mortality were not significantly affected when broilers were fed lower levels of Cu, Mn and Zn (organic and inorganic) compared with broilers fed the commercial inorganic levels of these trace minerals over the entire trial period. Feeding Cu, Mn and Zn (HMTBA)2 chelates at levels of 8, 32 and 32 mg/kg, respectively, resulted in the largest final mean body weight and body weight gain at 35 days of age, while maintaining a similar FCR. Carcass traits were mostly not affected by the different trace mineral treatments; whilst feeding 30, 32, and 32 mg/kg Cu, Mn and Zn (HMTBA)2 chelates resulted in a significant increase in percentage of carcass yield in comparison to all other treatment diets. At 21 days of age the negative control treatment resulted in a significantly higher presence of foot pad dermatitis in comparison to all other treatments. At 35 days of age the feeding of Cu, Mn and Zn- (HMTBA)2 resulted in a significant reduction of foot pad dermatitis and thus more saleable paws in comparison to the inorganic sulphate treatments. A lower average carcass scratch length and higher ileum strength were both observed from the supplementation of (HMTBA)2 chelates. The analysed Cu and Zn liver concentrations were significantly similar between the positive control, and the (HMTBA)2 treatments (P >0.05). The Mn liver concentrations were significantly higher for the positive control treatment in comparison to the (HMTBA)2 treatments(P < 0.05).
The dermis length and dermis area were significantly lower for the negative control treatment in comparison to all other treatments when comparing all grade 1 samples at 21 days of age. The epidermis length of foot pad skin samples were largest for the (HMTBA)2 8:32:32 treatment when comparing all foot pad dermatitis grade 1 samples taken at 35 days of age . The stratus corneum area and epidermis area increased from a foot pad dermatitis grade of 1 to grade 3 for samples taken at 21 and 35 days of age. At 35 days of age the grade 5 samples had the largest measurement for the stratus corneum area and epidermis area in comparison to all other grades.
From this study it may be concluded that organic trace minerals of (HMTBA)2 metal chelates may be supplied in broiler rations at much lower levels than the currently utilised commercial levels of inorganic trace minerals without having any adverse effects on the performance and carcass characteristics of birds. The results suggest that organic trace minerals may provide a viable tool for improving broiler production and overall profitability through improved flock uniformity, improved foot pad health and increased intestinal strength.