Early feed restriction of broilers: effects on abdominal fat pad, liver, and gizzard weights, fat deposition, and carcass composition.

A total of five experiments were conducted to investigate the effects of early feed restriction on organ weights, fat deposition, and carcass composition in broilers. In Experiments 1 and 2, broiler chicks were reared in litter pens for 49 days, whereas Experiments 3, 4, and 5 were conducted in battery cages for 28 days. Feed restriction in all experiments was accomplished by providing male broiler chicks 40 kcal per bird per day for 7 (Experiments 1 and 2) or 6 (Experiments 3, 4, and 5) days, starting at 4 days of age. Feed restriction of broiler pullets in Experiment 1 was imposed from 4 to 9 days of age. Furthermore, the starter and grower diets in Experiment 2 contained either 1 or 4% added fat and the starter diets in Experiments 3, 4, and 5 contained either 21 or 26% protein. No significant differences were observed for abdominal fat pad and gizzard weights, liver and carcass fat, or carcass protein between early restricted birds and ad libitum controls at 49 days of age in Experiments 1 and 2. Furthermore, with the exception of Experiment 4, no differences in abdominal fat pad weights were observed among the different feeding regimens. Significant increases in abdominal fat pad weights, percentage liver, and percentage carcass fat were noted for females at 49 days of age when compared with male broilers. Carcass fat was significantly higher and carcass protein was significantly lower in broilers fed commercial versus reduced fat diets. Broilers fed a 21% protein diet had significantly heavier abdominal fat pad weights at 28 days of age than birds fed a 26% protein diet.