The effect of feed form and herbage available on performance of broiler in free range system

This study was designed to investigate the effect of feed form (ground or pellet) and vegetation cover (available or unavailable) on the growth performance, some organ weights and carcass characteristics of slow growing broiler chickens grown in the free pasture system in a 2x2 factorial design. A total of 800, day-old slow-growing broiler chickens (Hubbard Isa Red-JA 87) were randomly alloted into 4 dietary treatments, each with 4 replicates of 50 birds. Each cage had a 4.5 m2 closed shelter area (2.2 m height, 1.5 m width and 3.0 m length) and 100 m2 open cage area. During the experiment, the duration of the natural day length was approximately 14 hours.Feeds (22%, 19% and 17% CP and all having 3000 Kcal/kg ME) were provided based on age (starting 1- 24 days, growing 25-48 days and finishing 49-72 days) of broiler chickens, respectively. The distribution of particle sizes was determined by the use of a shaking screen (Retsch shaker-AS 200; Retsch, Stuttgart, Germany). Feed and water were given as ad libitum to chicks. On days 24, 48 and 72 of the experiment, all animals were individually weighed and feed consumption and feed utilization rate were determined based on cage feed consumption. At the end of the experiment, 12 broiler chickens were slaughtered from each group. The carcass weights, carcass yield, visceral weights (stomach, cunt, liver, spleen and pancreas), intestinal length (small intestine, large intestine and blind intestine) and abdominal fat weight were determined for slaughtered chickens. Data obtained from the experiment were analysed with 2x2 factorial designs using of SPSS statistical package program. The effect of feed form was much more pronounced than forage intake in terms of body weight gain and feed conversion ratio with significant improvements in favour of pellet feeding. Throughout the experimental periods of 25 to 48 and 49 to 72, chicks fed on pelleted diet gained more body weight (P <0.01) which accompanied to lower feed conversion ratio (P <0.01) compared to those receiving ground feed . Pelleted diet decreased (P <0.05) feed consumption in birds between 25 to 48 days as compared to birds on ground feed. However, this tendency disappeared thereafter and no significant difference was found between treatments all through the experimental periods (P> 0.05). Carcass yield of broiler chicks slaughtered at 72 days of age was not significantly affected by either feed form or herbage intake during the outdoor access (P> 0.05). Administration feed in ground form significantly increased (P <0.01) the percentage weight of drumstick and breast meat, and length of the small intestines whereas decreased (P <0.01) neck, back and abdominal fat weight in relation to those fed on pellets. Herbage intake increased (P <0.01) relative neck weight in birds as compared to those unavailable herbage group. Overall results of this study suggest that pelleting the feed have substantial potential to improve live weight gain and feed conversion efficiency in slow growing broiler strain independent of the herbage intake as compared to ground feed. However, the effect of herbage intake on production variables and meat yield is almost negligible in broiler chicken. The negative implications of pelleting on carcass parts with economic importance are conclusive and warrants further studies in this field.