Effect of melatonin implants on carcass characteristics and meat quality of slow-growing chickens

This study evaluated the effect of melatonin implants on carcass characteristics and meat quality of slow-growing broilers slaughtered at 43 and 97 days (d) of age. A total of 128 one day-old male broilers (Coloryeld) were randomly divided into two groups, which in turn were divided into 8 groups (replicates) of 8 broilers each one. One group (64 animals) was the control group (C) and the other received a melatonin implant (18 mg melatonin per animal) at 8 d of age (M). The animals were reared for 97 d. For the first 42 d they were kept in an enclosed facility and then allowed access to the outside. Two culls were performed: one at 43 d and one at 97 d, randomly selecting 8 chicks from each group at each time (N = 8 × 2 × 2= 32). Carcass traits and meat quality were evaluated on these samples. Chickens slaughtered at older ages had higher dead-plucked, leg and carcass weights (P < 0.05). In terms of meat quality, chickens slaughtered at 97 days had higher L* (P < 0.001), lower a*, b* and chroma values (P < 0.01), as well as lower pH (P = 0.006), higher shear strength (P < 0.001), water holding capacity (P < 0.001) and water activity (P = 0.036). The melatonin implants did not influence carcass characteristics (P>0.05). Luminosity, tone and water activity decreased with melatonin implants at 43 d of age (P < 0.001), whereas pH increased (P = 0.004). At 97 d after slaughter, meat yellowness was lower (P = 0.028) and firmness increased (P = 0.029). At both time points, melatonin caused reddening of the meat (P < 0.001). Lipid oxidisability tended to be reduced, extending the shelf life of the meat (P = 0.068). The fatty acid profile was little affected by the placement of the implants. Age and melatonin have different effects on the meat quality of slow-growing chickens. While age affects several factors such as texture and fatty acid profile, melatonin improves colour, water activity and lipid oxidation. Its use could improve preservation and extend the shelf life of meat.