Abstract: [Objective] The aim of the present study was to assess the effects of dietary supplementation of pumpkin seed shells on growth performance, serum biochemical parameters, immune indexes, and hormone levels of Simmental crossbred cattle at different growth stages. [Method] A total of 40 male Simmental crossbred cattle in good body condition were selected and divided into the following 5 groups based on body weights: experimental group 1 （n=8, around 300 kg）, experimental group 2 （n=8, around 400 kg）, experimental group 3 （n=8, around 500 kg）, experimental group 4 （n=8, around 600 kg） and experimental group 5 （n=8, around 700 kg）. All of the experimental cattle were raised in separate pens. For each group, pumpkin seed shells were supplemented to the basal diet at a ratio of 10%. The experimental period was 90 days comprising a 20-day pre-trial and a 70-day formal trial. The body weight and feed intake of the experimental cattle in each group during the experiment were recorded, and the average daily weight gain, average daily feed intake and average feed to weight gain ratio were calculated. At the end of the experiment, blood samples were collected to prepare serum. Serum biochemical parameters, immune indexes and hormone levels were measured. [Result]As the body weights elevated, the daily feed intake of the experimental cattle gradually increased. The average daily feed intake of experimental groups 4 and 5 was significantly （P<0.05） higher than the other groups. The average feed to weight gain ratio in experimental group 1 was the lowest and significantly （P<0.05） lower than the other groups. Compared to experimental groups 1 and 3, the serum contents of total protein （TP） and blood urea nitrogen （BUN） in experimental group 4 were significantly （P<0.05） higher. Experimental group 2 had significantly （P<0.05） higher serum immunoglobulin M （IgM） content than the other groups. In comparison to experimental groups 3, 4 and 5, experimental group 1 had significantly （P<0.05） higher serum cortisol （COR） level. Experimental group 5 had significantly （P<0.05） higher serum calcitonin （CT） level than the other groups. The C-reactive protein level in experimental groups 4 and 5 was significantly （P<0.05） higher than experimental group 1.[Conclusion]Supplementation of pumpkin seed shells in the basal diet of Simmental crossbred cattle could increase the feed intake and improve protein utilization efficiency, and also had certain effects on enhancing immunity. It can be developed and utilized as a roughage resource.

Key words: pumpkin seed shell, Simmental crossbred cattle, growth performance, serum biochemical parameter, serum immune index, serum hormone level