Effect of dietary fat and lighting programme on broiler skin strength and elasticity related to skin tearing

Abstract

Three trials were conducted to evaluate the influence of dietary fat and light programmes during rearing on skin quality of a total of 7800 broilers to resist plucking stress. Experimental treatments were two light programmes of light:dark hours in trials 1 (24:0 and 16:8) and 2 (21:3 and 16:8), and two dietary fat sources of animal fat (AF) and soy bean oil (SBO) in trial 3. Within each trial the broilers were reared in separate pens of each replicate (n = 4) in two similar houses. The total frequency of skin tears and downgraded skin tears caused by the plucking process were registered by visual examination of 325 broilers from each replicate after plucking, and all carcasses were weighed individually. Broilers with intact skin and with skin tears were removed from the slaughter line and after air chilling, breast skin samples with dermis and hypodermis were cut and used for skin tensile strength and elasticity measurement.

Light programmes with long dark periods during raising of broilers reduced skin tearing at the processing plant. The use of soy bean oil as dietary fat source in comparison with animal fat increased the skin tearing frequency (P = 0.066) and showed slightly reduced skin elasticity. Skin tears were more frequent among female broilers, and they had a lower skin tensile strength (P < 0.001) and elasticity (P < 0.01). An overall positive correlation between broiler weight and skin tears was found and a negative correlation between frequency of skin tears and breast skin elasticity was found for female broilers, whereas skin strength showed less connection to skin tear occurrence.

Key words:

• chickens
• carcass
• downgrades
• fatty acids
• processing
• slaughter