Excessive dietary vitamin D supplementation as a risk factor for sudden death syndrome in fast growing commercial broilers

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2007-12, Vol.148 (4), p.828-833
• Main Authors: Nain, S., Laarveld, B., Wojnarowicz, C., Olkowski, A.A.
• Format: Article
• Language: English
• Subjects: Acute heart failure; Animal Feed; Animal Nutritional Physiological Phenomena; Animals; Arrhythmias, Cardiac - etiology; Arrhythmias, Cardiac - mortality; Broiler; Cardiac arrhythmia; Chickens; Dietary Supplements; Electrocardiography; Exercise Test; Heart Rate; Male; Mortality; Myocardium - pathology; Poultry Diseases - mortality; Risk Factors; Time Factors; Vitamin D; Vitamin D - adverse effects
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2007.08.023

Broiler diets are frequently fortified with vitamin D (D 3) above the recommended levels in an attempt to prevent commonly occurring leg problems. Since the basal levels of dietary D 3 are rarely known, there is a risk of over-supplementation. Over-supplementation of D 3 has been shown to have detrimental effects on the heart. Sudden death syndrome (SDS) is a condition commonly observed in broiler flocks and is associated with acute heart failure. The present study examines the effects of excessive levels of vitamin D 3 on cardiac health in fast growing broiler chickens. Commercial male broilers ( Gallus gallus) were exposed to either a commercial diet or a commercial diet supplemented with D 3. Throughout the trial all birds were monitored several times daily for overt signs of heart disease, and periodically electrocardiographic measurements were obtained. Morbidity and mortality data were collected daily. On day 32 a simulated stress challenge consisting of a single injection of epinephrine (100 μg/kg BW) was administered under continuous ECG monitoring. Broilers fed the high D 3 diet were 2.5 fold more likely to succumb to acute heart failure and die of SDS ( p < 0.05). Electrocardiographic examination showed a higher rate of cardiac arrhythmia in birds fed the high D 3 diet (22.6%), in comparison to those fed the control diet (11.8%). The stress challenge test revealed that broilers exposed to high dietary D 3 were more susceptible to ventricular arrhythmia. Our findings indicate that over-supplementation of vitamin D increases the risk of SDS in broilers, and that the most likely mechanism is associated with increased susceptibility of the ventricular myocardium to arrhythmia.