[Differentiation of fattening and slaughtering performance and carcass quality of broiler genotypes with and without the dwarf factor and fast or slow feathering under heat stress].

Abstract

In a comparative study the influences were tested of the origins NWR (normal-growth White Rocks) and ZWR (dwarf-growth White Rocks) with a speed for slow (K) and fast (k) feathering as well as the effect of a high environmental temperature (UT, 32 +/- 2.5 degrees C) on the fattening and slaughtering performance of male broilers and their meat quality. Also investigated were effects of these factors on the fatty acid pattern of the two valuable parts--breast and leg. Dwarf broilers kept under high UT had a lower liveweight (LM8) in their 8th week as compared with NWR and animals kept under the usual UT. No influence was found of the feathering on the fattening and slaughtering performance. The effect of heat stress (high UT) and of the dwarfing gene on the breast and leg parts was statistically highly significant (P < 0.001). Dwarfed broilers and animals under normal UT exhibited a smaller slaughtering proportion as compared with normal animals and animals under a higher UT. The abdominal fat content was significantly higher under heat stress. Meat quality showed no dependence on the origin or the climatic conditions. In the fatty acid analysis no dependence could be detected of the FS pattern on the origins (genotypes), whereas an effect was found of the UT on some unsaturated and saturated fatty acids. Palmitic acid and stearic acid formed the largest part of all saturated FS investigated. Among the unsaturated FS the oil, linoleic, and palmitic acids reached the highest share. The effect of higher UT was not uniform in the FS pattern. The sum of saturated FT was increased under heat stress, thus suggesting a more favourable fat quality of the meat.