DIETARY AND ENVIRONMENTAL-FACTORS AFFECTING SKIN STRENGTH IN BROILER-CHICKENS

Two experiments were conducted to evaluate dietary and environmental f actors involved in skin tensile strength of commercial broilers. In Ex periment 1 the effect of added dietary fat (4 or 7%), environmental te mperature (25 or 20.5 C after 21 d), and anticoccidial drug (halofugin one or salinomycin fed continuously) were examined factorially using m ale and female chicks. Skin tensile strength was measured at 21, 35, a nd 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 anticoc cidial drug (halofuginone or salinomycin) were examined factorially us ing 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 s trength in either experiment. Continuous feeding of halofuginone signi ficantly (P < .0001) decreased skin strength compared with that of bir ds fed salinomycin in both experiments. Halofuginone reduced skin stre ngth in females more than males (25 and 9%, respectively). Dermis thic kness was correspondingly reduced in the birds consuming halofuginone. In Experiment 2, soluble collagen contents were reduced at all ages i n birds consuming halofuginone; insoluble collagen was significantly d ecreased at 21 d of age. Birds with weakened skin exhibited increased incidence of skin tears during slaughter in a commercial processing pl ant (P less than or equal to .0043).These results suggest that halofug inone interferes with collagen synthesis, causing decreased collagen f ormation and reduced skin strength. Neither added dietary fat nor ambi ent temperature were involved.