Abstract: The aim of this experiment was to study the effects of different crude protein levels of artificial pigeon milk on growth performance, serum antioxidant and intestinal development of the suckling pigeons in order to determine a reasonable crude protein level of artificial pigeon milk. One hundred and ninety-two 7-day-old suckling pigeons were randomly divided into 4 groups with 8 replicates and 6 suckling pigeons in each group. They were fed artificial pigeon milk with crude protein levels of 16.5%, 18%, 19.5% and 21% (CP16.5%, CP18%, CP19.5% and CP21% groups), respectively, for 18 days. The results were showed as follows:1) There were no significant differences in initial body weight, final body weight, average daily gain (ADG), average daily feed intake (ADFI) and feed/gain ratio (F/G) among the groups of suckling pigeons(P>0.05). 2) The carcass rate of suckling pigeons in CP21% group was the highest and significantly higher than those of CP18% and CP19.5% groups (P<0.05); The half-evisceration rate in CP16.5% group was the highest and significantly higher than that in CP19.5% group (P<0.05); There was no significant difference in the evisceration rate among all groups (P>0.05); The breast muscle rate in CP21% group was the highest and significantly higher than that of CP18% group (P<0.05). 3) The apparent metabolic rates of crude protein, crude fat and dry matter in the CP16.5% group were the highest, but only the apparent metabolic rates of crude protein and dry matter in the CP16.5% group were significantly higher than those of the other groups (P<0.05), and there was no significant difference in the apparent metabolic rates of crude fat among all groups (P>0.05). 4) The spleen index was significantly higher in the CP18% group than other groups (P<0.05); The kidney index in the CP16.5% group was significantly lower than other groups (P<0.05); The gizzard index in the CP16.5% group was the highest and significantly higher than other groups (P<0.05); The bursal index in the CP16.5% group was the highest and significantly higher than the CP21% group (P<0.05); The heart, liver and glandular stomach indices of the suckling pigeons had no significant difference among all groups (P>0.05). 5) The height of the duodenal villi in the CP21% group was significantly lower than those of the other groups (P<0.05), the depth of the duodenal crypt had no significant difference among all groups (P>0.05), and the ratio of the duodenal villi height to crypt depth (V/C) ratio in the CP21% group was significantly lower than those of the CP18% and CP19.5% groups (P<0.05). The jejunum and ileum morphology index had no significant difference among groups (P>0.05). 6) Serum malondialdehyde in the CP16.5% group was significantly lower than the CP21% group (P<0.05), while serum total antioxidant capacity, catalase and superoxide dismutase levels among all groups had no significant difference (P>0.05). In conclusion, the crude protein level of artificial pigeon milk at 16.5% to 21% could maintain the normal growth performance of pigeons, and with the increase of crude protein level of artificial pigeon milk, the carcass rate and breast muscle rate of pigeons increased, but the serum antioxidant capacity decreased. The highest crude protein apparent metabolic rate was found at 16.5% crude protein level of artificial pigeon milk, and it could meet the nutritional needs of growing pigeons. Therefore, the crude protein level of artificial pigeon milk is recommended to be 16.5% under the conditions of this experiment.

Key words: squab pigeon, artificial crop milk, crude protein level, growth performance, intestinal development