Effects of feeding rate on growth,body composition and blood index of Acipenser gueldenstaedtii reared in net pens

Russian sturgeon( Acipenser gueldenstaedtii) has a high nutritional value and economic value.Feeding rate,water temperature and fish size are three important factors affecting the growth of fish. Feed ration has a direct impact on farming costs. High feed ration will waste feed,increase production costs and pollute aquaculture water. Low feed ration can hinder fish growth, reduce immune function, increase morbidity and even cause death,and thus determining the optimal feeding rate is important. This study described the effects of five feeding levels on growth,body composition and main blood index of Russian sturgeon,in order to find the best feeding rates with economic and ecological requirements. Mean body mass( 3381. 27 ± 132. 17) g of 2-year-old Russian sturgeon juveniles artificially propagated by Hangzhou Qiandaohu Xunlong SCI-TECH Co.,LTD were selected. The fish were cultured in 6 m × 6 m × 6 m cages,each cage with 300 ind. Water temperature was 15- 20 ℃,with daily feeding rate 1. 0% as a benchmark,set 0. 7%( F1 group),0. 8%( F2 group),0. 9%( F3 group),1. 0%( F4 group) and 1. 1%( F5 group)five kinds of feeding levels,and each group with three parallels,fed twice a day. Experiments started from November 2013 and lasted for seven weeks. Stop feeding for 72 h at the end,and 30 ind in each group were randomly selected to measure total length,body length and body mass,and six ind were randomly selected to collect vein blood. The blood was divided into two,one stored in a centrifuge tube and allowed to stand overnight at 3 000 r·min- 1centrifugation for 10 min,and the serum sample to be tested was prepared; The other was stored in a vacuum blood collection tube containing heparin and complete blood cell count within 24 h. The experimental fish were dissected after the blood,liver,spleen and gonad were accurately weighed and muscle taken by- 25 ℃ cryopreservation for body composition analysis. Results showed that different feeding rates affected the growth of Russian sturgeon. With the increasing feeding rates,Russian sturgeon weight gain rate( WGR) and specific growth rate( SGR) increased. WGR and SGR were significantly( P 0. 05) higher in F5 than F1 group. And there were no significant differences between other groups( P 0. 05),it showed that feeding rate at 0. 8% did not significantly affect the growth performance. There was no change in survival rate( SR) and condition factor( CF) between any treatments( P 0. 05). Hepatosomatie index( HSI) were significantly( P 0. 05) higher in F5 than F1 group,Splenosomatie index( SSI) was not significantly different between any treatment( P 0. 05). Gonadosomatic index( GSI) were significantly( P 0. 05)higher in F5 group than F1 group. F2,F3,F5 group and F4 group were not significantly different( P 0. 05). It showed that increasing feeding rate helped gonadal development. Moisture in Russian sturgeon muscle was significantly( P 0. 05) higher at F1 group than F5 group,and other groups showed no significant difference. Crude protein and crude lipid were not significantly( P 0. 05) different at all feeding rates. Crude ash in F5 and F3 group was significantly( P 0. 05) lower that than in F2 and F1 group,and significantly higher in F4 group. With the increase of feeding rate,Russian sturgeon muscle moisture levels gradually decreased,and protein levels gradually increased. This phenomenon may be due to the fact that Russian sturgeon mainly used lipids as an energy source material when hungery,which was different from material to carbohydrates as an energy source during starvation. There was no change in red blood cell( RBC)amount,white blood cell( WBC) amount,total cholesterol( TC) between any treatments( P 0. 05). With the increasing feeding rate,although there is no significant difference in the number of RBC,an upward trend,which indicated higher feeding rates,may have a certain role in promoting the health of Russian sturgeon. Triglyceride( TG) was significantly( P 0. 05) higher in F4 and F5 group than F1 Group,and showed no significant difference from F3 and F2 group. Results showed that,F5 group of Russian sturgeon grew best,F1 group grew worst. It showed that 0. 7% feeding rate is inappropriate. There was no significant difference between F2,F3,F5 group and F4 group. From economic and ecological aspects,feeding rate can be reduced to 0. 8% from 1. 0% as a daily feeding rate to reduce farming costs,improve the economic and ecological benefits.