Performance of broilers fed limited quantities of feed or nutrients during seven to fourteen days of age.

Three experiments were conducted with male broilers to study the effects of early life undernutrition. In all studies, treatments were represented by three or four replicate floor pens, each containing 30 to 40 birds. In Experiment 1, broilers were fed at 0.75 kcal ME/gBW0.67 for 4 d, 1.5 kcal ME/gBW0.67 for 5 d or 2.25 kcal ME/gBW0.67 for 6 d, all imposed beginning at 6 d of age. Birds were smaller following feed restriction (P < 0.01) although growth compensation occurred, and at 49 d all restricted birds were heavier (P < 0.01) than full-fed control birds. Improved growth was associated with improved feed conversion (P < 0.01), although carcass composition was unchanged. In a second study, birds were fed at 0.75 kcal ME/gBW0.67 for 3, 4, or 5 d, starting at either 4, 7, or 10 d of age. When feed restriction was applied early, or for shorter periods of time, growth compensation occurred (P > 0.05). With other more severe feed restriction, birds were smaller (P < 0.05) at 49 d compared to controls. Feed conversion was improved following prior feed restriction (P < 0.01, 0 to 49 d). In a third trial, broilers were fed a starter diet diluted with 50% oat hulls. Birds failed to consume enough of this diluted feed, and so were initially smaller. However 49-d weight was not affected (P > 0.05). When periods of 24-h feed withdrawal were imposed in conjunction with the diluted diets, birds were underweight at 49 d. It is concluded that physical feed restriction at 0.75 to 1.5 kcal ME/gBW0.67 imposed for 3 to 4 d in the second week of life currently presents the best option as a means of controlling broiler growth so as to improve feed efficiency.