[Effect of the gas composition of the air on the growth of broilers]

Comparative investigations were carried out with the gas composition of air and the productivity of broilers raised in cells and on deep litter in the region of Northeast Bulgaria. The buildings were sized 75 X 15 X 3.8 m. The air exchange in them was effected through mechanical ventilation at lowered pressure, after the pattern 'from above--sideways'. As many as 17.3 birds/m2, when deep litter was used, and 28.6 birds/m2, when cells were used, were housed in the buildings for raising up to the age of 56 days. The content of harmful gases, such as ammonia, hydrogen sulfide, and carbon dioxide was determined at 14-day intervals at 3 sites in the buildings. The body mass of broilers, raised after the two methods, was followed up on the 14th, 28th, 42nd, and 56th day of age. The number of birds and the live mass produced per square meter of floor area in the various seasons of the year were calculated at the end of the fattening periods. It was found that by the end of fattening on deep litter the concentration of ammonia varied around the upper admissible threshold, while with fattening in cells it was within the standard range. With cell raising of broilers the live mass produced per 1 m2 of flooring was 50.5 to 83.6 per cent more as compared with the live mass produced on deep litter. The total broiler produce with cell raising over the 4 seasons was 63.3 per cent, on an average, more than that with the use of deep litter.