To evaluate the effects of duck hepatitis virus-1(DHV-1) on the body weight gain in duck and the effects of silymarin on it in vivo,100 10-d-old ducks,both male and female,were collected to be subjected to the test.The experiments were conducted in 8 groups:in group 1-3,the animals were inoculated with 1:105 diluted duck hepatitis virus(DHV-1) infected allantoic fluid and given 0,30,and 50 mg kg-1 BW d-1 silymarin orally,respectively.In group 4-6,the animals were inoculated with 1:5 × 105 diluted DHV-1 infected allantoic fluid and given 0,10,and 30 mg kg-1 BW d-1 silymarin orally,respectively.In group 7,the animals were given 10 mg kg-1 BW d-1 silymarin only.Group 8 was the control one treated by injecting sterillized saline into the leg muscles.All the silymarin was given from 0 to 4 d after inoculation of the virus.By the 5th d after inoculation,the vein blood was drawn from the dorsal foot vein and the plasma samples were collected and stored at-20°C.The body weight gain(BWG) was measured from 0 to 10 d after inoculation.The plasma IGF-I,T3,and T4 concentrations were measured by radioimmunoassay(RIA).At the virus dose of 1:5 × 105 diluted virus infected allantoic fluid,the inoculation of the virus enhanced the BWG significantly compared with that of the control(P < 0.01),while 10-50 mg kg-1 BW d-1 silymarin could counteract the effects of the virus on the BWG dose-dependently.The plasma IGF-I levels showed no correlation with the BWG,but the T3 levels showed a same tropism with the body weight gain.The present results indicated that sublethal DHV-1 enhanced the body weight gain of ducklings significantly,and the silymarin could counteract this effect in vivo.
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