Potential effects of a phytogenic feed additive on carcass and meat traits in broilers compared to an antibiotic growth promoter

Plant origin (phytogenic) feed additives (PFA), comprising herbs, spices, essential oils, plant extracts and derived products have gained considerable interest in view of the worldwide ban on use of antibiotic growth promoters (AGPs) in food animals. These products have the ability to improve performance by maintaining a healthy gut environment (Windisch et al., 2008). They have also been reported to influence carcass and meat quality characteristics in agricultural livestock (Isabel and Santos, 2009; Hong et al., 2012). The present study was aimed at comparing the effects of a PFA and an AGP on carcass and meat traits in broiler chickens.

A 39 day trial was conducted with an as-hatched flock of 432 day-old Cobb 400 broilers. Chicks were randomly assigned to three dietary treatments with 12 replications per treatment and 12 birds per replicate. The three dietary treatments consisted of a control (basal diet only), AGP (basal diet + 225 mg/kg bacitracin methylene disalicylate), and PFA (basal diet + PFA Digestarom® Poultry 150 mg/kg). Birds received maize-soybean meal based diets from one to seven days (starter), eight to 21 days (grower) and 22 to 39 days (finisher). On day 39, 12 birds having body weight closest to the mean weight of the group were selected from each dietary treatment, weighed and killed by cervical dislocation, followed by exsanguination. Carcass yield and yields of breast, thighs and drumsticks relative to live weight (g/kg) were measured. Breast fillets were stored at 4o C for 24 hours for determination of pH, drip loss, moisture and crude protein contents. Moisture in meat was determined in triplicate by drying ground breast meat sample at 98o C for 24 hours. Meat protein (Nitrogen x 6.25) was determined in duplicate by the Kjeldahl method (AOAC, 2005). Drip loss and pH were determined according to Qiao et al. (2007). Pieces of breast fillet were stored at 4o C for 48 hours and the loss of weight as the percentage of the original sample weight was determined. Meat pH was measured at six different locations across the sample surface with a pH meter (AB15, Thermo Fisher scientific, Waltham, MA). The average represented the ultimate pH of the sample.

Except for the yield of drumsticks, which was higher in the AGP and PFA groups as compared to the control (P = 0.002), the carcass traits generally remained unaffected by the diets (P > 0.05). Relative organ weights were also not affected due to supplementation of AGP and PFA to the diet (P > 0.05); however, weight of the viscera decreased (P = 0.004) in the dietary groups receiving AGP and PFA supplementation. The reduction in viscera weight by dietary supplementation of AGP and PFA implied a reduction in the energy required to maintain the gut, thereby leaving more energy available for productive processes such as body weight gain (BWG) and better feed conversion ratio (FCR) as reflected in the trial with significantly higher BWG and reduced FCR in PFA and AGP groups (P = 0.001). No significant effect of the diets was observed on drip loss and pH of meat although the PFA group tended to have a lower meat pH compared to the other two groups (P > 0.05).

The PFA evaluated in this study was equally effective to the AGP used, as far as the carcass and meat traits of the birds are concerned when added to a maize-soybean meal-based coccidiostat-free broiler diet and thus can serve as an alternative to the AGPs in broiler production.