Effect of bromine and iodine in drinking water on the physiological parameters of broilers

Abstract

Assessment of a significant number of water samples across South Africa by Casey and Meyer over a number of years, revealed that high concentrations (30- 32 mg/L) of bromine (Br) occur naturally within groundwater in South Africa, hence a potentially hazardous chemical constituent (PHCC). Br, the only liquid non-metallic element, is ubiquitous and an abundant trace element, but it has not been conclusively shown to perform essential functions in plants, micro organisms or animals (NRC, 2005). The recommended limit (maximum limit for no risk) for Br in drinking water was set at 1 mg/L by Kempster et al. (1980); Casey and Meyer (2001) recommend the relevant safety guideline for Br to be 0.01 mg/L. The aim of this project was to establish the effect of Br and iodine (I) in drinking water on the physiological parameters of broilers. This will contribute to verifying and refining water quality guidelines. The effect of six treatments administered as sodium bromide (NaBr) and potassium iodide (KI): 0 mg Br/L and 0 mg I/L; 1 mg Br/L; 1mg Br/L and 0.7 mg I/L; 0.7 mg I/L; 3 mg Br/L; 3 mg Br/L and 0.7 mg I/L, in the drinking water of 540 mixed Ross broiler chickens was investigated. The trial ran over a 42-day growth period from Day 1 post-hatching where mortalities, water and feed intakes were recorded daily. Chickens were weighed weekly and slaughtered at 4 and 6 weeks of age. Blood samples were taken before slaughter and free T3 and T4 hormone levels were quantified. Thyroid gland, liver and kidney samples were analysed for Br and I quantity. The different treatments of Br, irrespective of I, significantly decreased water intake (P=0.0232) and feed intake (P=0.0035) over the 42 days. The overall interaction of Br and I had no significant effect on water (P=0.0928) and feed (P=0.9593) intakes thus I did have an effective ameliorating effect on Br. FCR, weight gain and mortalities were not significantly affected by Br intake. This was also found for free T3 and T4 hormone levels. Br had an overall effect on the thyroid gland (P=0.0457), liver (P=0.0025) and kidney (P=0.0032) with accumulation of the PHCC within these three organs. It was apparent that 1 and 3 mg Br/L water administered to broilers or ingestion rates of 1.59 and 4.44 mg Br/L per bird per day, over a production period of 42 days did affect the production parameters of the birds sub-clinically. Another derivation to refine the water quality guidelines was that the administration of 0.7 mg I/L water or ingestion rates of 1.1 mg I/L per bird per day did alleviate the severe detrimental effect of the high PHCC. The 3 mg Br/L guideline is thus not too restrictive. Further research exposing the animals for a longer time period (exceeding 42 days) and exposing mature animals (producing nutritional products for human consumption) to these treatments would assist in quantifying these results.