Study on Dietary Factors Pertinent to the Pathogenesis of Heart Failure in Fast-growing Commercial Broilers

by Nain, Sukhbir

A series of seven experiments were conducted to evaluate the risk of acute (sudden death syndrome; SDS) or chronic (congestive heart failure; CHF) heart failure associated with dietary over-supplementation of vitamin A, vitamin D3, vitamin E, vitamin C or cardiotoxic factors present in meat meal. The risk of heart failure associated with the above mentioned dietary factors was tested followed by gross, microscopic, ultrastructural and biochemical investigation for mechanisms associated with mentioned risk factors. Simultaneously, the molecular mechanisms underlying the deterioration of heart function in fast-growing commercial broilers were studied. Each compound was tested separately at a concentration higher than the recommended levels. The basic experimental unit comprised groups of 40 to 50 day old male broiler chickens at the start of experiment. Lowered thermal brooding temperature protocol, an approach resulting in clinical manifestation of heart failure in practically all broilers predisposed to heart disease, was used.

Broilers fed the vitamin D3 enriched diet were 2.5 fold more likely to succumb to acute heart failure (p<0.05). Simulated stress challenge with epinephrine revealed that broilers fed excess of vitamin D3 were more susceptible to ventricular arrhythmia. The risk of CHF was higher (P<0.05) in broilers fed the vitamin D3, vitamin A and methanol soluble extract from meat meal enriched diets as compared to groups fed the control diet. The incidence of CHF in broilers fed the diet fortified with vitamin E was not significantly different as compared to the control group, whereas supplementation of vitamin C in the diet tended (p=0.10) to reduce the incidence of CHF. The level of malondialdehyde equivalents, an indicator of lipid peroxidation, was significantly higher (p<0.05) in myocardium of broilers developing CHF irrespective of dietary factors. Antioxidant vitamins (E and C) did not prevent lipid peroxidation in broilers developing CHF.

In conclusion, the present findings indicate that over-supplementation of vitamin A and D3 increases the risk of heart failure in broilers. Meat meal contains some unknown cardiotoxic factors, capable of precipitating heart conditions in susceptible broilers. Oxidative stress is involved in the pathogenesis of heart failure in broilers, but supplementation of antioxidant vitamins did not prevent oxidative damage in broilers that developed CHF. The oversupplementation of vitamins (A and D3) should not be encouraged in broilers diet as they may increase the economic losses to broilers industry subsequent to heart related mortalities/morbidities.