In order to
study t
he effect
s of dietary emodin,
hig
h-do
se vitamin C (Vc) and t
heir combination on growt
h of Wuc
hang bream (
Megalobrama amblycephala Y.) and it
s re
si
stance to
hig
h temperature
stre
ss, 1200
healt
hy Wuc
hang bream wit
h initial body weig
ht of 133.44聽卤聽2.11聽g were randomly divided into four group
s: a control group fed wit
h ba
sal diet (containing 50.3聽mg/kg Vc) and t
hree treated group
s fed wit
h ba
sal diet
s supplemented wit
h 60聽mg/kg emodin, 700聽mg/kg Vc, and t
he combination of 60聽mg/kg emodin聽+聽700聽mg/kg Vc, re
spectively. After feeding for 60 day
s, t
he growt
h performance of Wuc
hang bream wa
s mea
sured. T
hen 25 fi
sh per tank were expo
sed to
heat
stre
ss of 34聽掳C. T
he bioc
hemical parameter
s of blood and liver, and expre
ssion level
s of liver two HSP70
s mRNA before and after
heat
stre
ss were determined and t
he cumulative mortality of eac
h group under
heat
stre
ss wa
s counted. T
he re
sult
s showed t
hat before
stre
ss, compared wit
h t
he control, t
he weig
ht gain (WG) and
specific growt
h rate (SGR),
serum total protein (TP), ly
sozyme (LSZ), and alkaline p
ho
sp
hata
se (ALP) level
s, liver
superoxide di
smuta
se (SOD) activity and expre
ssion level of HSP70 mRNA
significantly increa
sed in emodin and Vc group
s w
hile feed conver
sion rate (FCR),
serum corti
sol (COR), triglyceride (TG) and liver malondialde
hyde (MDA) content
s decrea
sed (
P聽<聽0.05); liver catala
se (CAT) activity al
so
significantly increa
sed in emodin group (
P聽<聽0.05). Alt
houg
h serum TP, LSZ, and liver HSP70 mRNA level
s significantly increa
sed and liver MDA level decrea
sed in combination group (
P聽<聽0.05), no
synergi
sm wa
s ob
served.
After heat stress, compared with the control, the serum TP, LSZ, ALP levels, liver SOD, CAT activities, and expression levels of HSC70 and HSP70 mRNAs increased in emodin and Vc groups in varying degrees and serum COR, glucose, glutamic-pyruvic transaminase (GPT), glutamic-oxaloacetic transaminase (GOT), TG and liver MDA levels decreased to some extent. Although these parameters had similar changing trend as above ones in combination group, it did not show any synergism either. Statistics showed that under heat stress, the cumulative mortalities of emodin and Vc groups, except at 6聽h in emodin group, were significantly lower than that of the control (P聽<聽0.05) while the difference between the combination and control groups was not significant (P聽>聽0.05). Thus, the basal diet supplemented with 60聽mg/kg emodin or 700聽mg/kg Vc could promote the growth of Wuchang bream, reduce FCR, increase non-specific immunity of fish, antioxidant capacity, and two HSP70s mRNA expression levels, and enhance resistance to heat stress in fish. However, the combination of emodin and high-dose Vc showed no better effect.