1. Male chickens, 1 week old, were fed alternately for 6 or 12 h periods with diets complementary in their amino acid composition. The isonitrogenous, isoenergetic diets were based on fish meal or sunflower meal as the sole source of protein, or fish meal–sunflower meal (40:60, w/w); each diet contained 120 g crude protein/kg. Other groups of chickens were given these diets ad lib.
Net protein utilization (NPU) values obtained after a 1-week experimental period indicated that sequential feeding for both 6 and 12 h resulted in significantly improved responses compared with chickens given the same diets ad lib. These results suggested that the two protein sources, although provided at separate times, could complement each other.
2. In certain treatments there was a 6 or 12 h fasting period between feeding periods to reduce the effect of nutrients from the previous period.
3. For alternate feeding and fasting periods of 6 h with the combined diet, food intake and gain in body-weight were both significantly reduced compared with the corresponding values for the combined diet fed ad lib. The NPU value was virtually the same for both treatments. For 12 h periods of alternate feeding and fasting the gain in body-weight was only just significantly lower than that for the control group (combined diet fed ad lib.), but the NPU value was highly significantly better than that for the control group.
4. For the treatments which included 6 and 12 h fasting periods between the two singleprotein diets, the food intake and gain in body-weight were significantly lower compared with the treatment groups given alternate feeding and fasting periods of either 6 or 12 h with the combined diet. The NPU values for the two groups given 12 h alternate feeding and fasting periods differed significantly, whereas the NPU values for the two groups given 6 h feeding and fasting periods were the same.