Abstract
OBJECTIVE: An experiment was conducted to evaluate the effect of different levels of crude protein (CP) and two rearing systems (cage and floor), on blood parameters and digestive and reproductive organ development of brown laying hens. METHODS: A total of 400 Hisex Brown laying hens between 30 and 45 weeks of age were distributed in a completely randomized design and a 2×4 factorial arrangement, with main effects including two rearing systems (cage and floor) and levels of CP (140, 150, 160, and 180 g/kg), in a total of eight treatments and five replicates of 10 birds each with initial body weight of 1,877 g (laying hen in cage) and 1,866 g (laying hens in floor). The parameters evaluated were plasma total protein, albumin, uric acid, total cholesterol, relative weights of oviduct, abdominal fat, liver, gizzard, crest and dewlap, length of small intestine and oviduct. RESULTS: The blood parameters were similar in birds reared in cage and floor systems. The birds reared on the floor showed greater small intestine and oviduct weight (%) and lower liver and pancreas weight (%). A significant interaction was observed between factors for the relative gizzard, crest and dewlap weight, serum protein, uric acid, and total cholesterol (p<0.05). The diets with 140 g/kg CP resulted in lower serum protein and lower cholesterol in birds reared in floor system, while birds reared in cage system showed no effect of CP on both parameters. Birds reared in cage and fed with 140 and 150 g/kg CP presented lower uric acid. The group of birds reared in floor system fed 180 g/kg had greater uric acid. CONCLUSION: The dietary protein level can be reduced up to 140 g/kg for Hisex Brown hens (30 to 45 weeks of age) without an important effect on metabolic profile and organ development in both rearing systems.