Dietary and environmental factors affecting skin strength in broiler chickens

Two experiments were conducted to evaluate dietary and environmental factors involved in skin tensile strength of commercial broilers. In Experiment 1 the effect of added dietary fat (4 or 7%), environmental temperature (25 or 20.5 C after 21 d), and anticoccidial drug (halofuginone or salinomycin fed continuously) were examined factorially using male and female chicks. Skin tensile strength was measured at 21, 35, and 40 d of age. Thickness of the dermal layers was measured from skin taken at Day 35. In Experiment 2, the effect of added dietary fat (0 or 7%), environmental temperature (25 or 18.5 C after 21 d), and anticoccidial drug (halofuginone or salinomycin) were examined factorially using female chicks. Skin strength and collagen content of the skin were measured at 21, 38, and 42 d of age. Skin tensile strength increased with age in both experiments, but female skin strength was subject to periodic decline. Males had significantly stronger skin than females. Levels of added fat or environmental temperature did not affect skin strength in either experiment. Continuous feeding of halofuginone significantly (P < .0001) decreased skin strength compared with that of birds fed salinomycin in both experiments. Halofuginone reduced skin strength in females more than males (25 and 9%, respectively). Dermis thickness was correspondingly reduced in the birds consuming halofuginone. In Experiment 2, soluble collagen contents were reduced at all ages in birds consuming halofuginone; insoluble collagen was significantly decreased at 21 d of age. Birds with weakened skin exhibited increased incidence of skin tears during slaughter in a commercial processing plant (P less than or equal to .0043). These results suggest that halofuginone interferes with collagen synthesis, causing decreased collagen formation and reduced skin strength. Neither added dietary fat nor ambient temperature were involved.