Effects of diet and breed on performance and electrocardiograms in broilers

Vita.Two "modern" commercial broilers breeds (Indian River: IR and Hubbard:HU) and one older broiler breed (Athens-Canadian Randombred:AC) were evaluated with respected to growth rate, feed conversion, carcass composition, and electrocardiograph (ECG) pattern analysis using two different feeding regimens (1963 and 1993). The 1963 diets were based on a diet published in the premier poultry nutrition book at that time (Handbook of Poultry Nutrition by W. Ray Ewing, 1963). Both starter and grower diets were fed. A total of 540 mix-sexed broilers were assigned to 18 floor pens. Body weight and feed conversion were measured at 2, 3, 4, 5, 6, and 7 weeks of age. The growth rate of the modern broiler breeds was markedly increased over the older AC line. The modern breeds (IR and HU) were at least four times heavier than the AC breed (AC) at the end of seven weeks (IR: 2526 g, HU: 2507 g vs. AC: 592 g). The difference between the two feeding regimens when fed to the same strain of broilers was much smaller and the improvement that could be attributed to the 1993 diets were approximately 5% of the total growth improvement. There were no significant treatment differences as a result of the 1963 or 1993 diets. All significant differences with respect to bird performance throughout the experiments were a result of breed; the modern IR and HU broilers exhibited much faster and more efficient rates of growth when compared to the AC broilers. There were five distinctive QRS-complex ECG patterns observed (RR, Rs, RS, rS, SS) on lead 11, III and aVF of modem broilers (IR and HU). Single Comb White Leghorn (SCWL) layers typically displayed three ECG patterns (RS: 2.8%; rS: 55.7% and SS: 41.4% respectively). The AC breed displayed four patterns (Rs: 2.8%; RS: 17.4%; rS: 8.7% and SS: 71% respectively). The right ventricular/body weight (RV/BW) ratio and the left ventricular/bodyweight (LV/BW) ratio of modern broiler breeds (IR and HU) were significantly smaller than those of the AC breed. There was a positive correlation between heart weight and R-wave; however, there was a negative correlation between heart weight and S-wave. The fact that different patterns of ECG were observed that it could be potentially useful as a tool aid broiler breeders in their selection process