| Two experiments were conducted to study the effect of EFA n-6/n-3 rate and lipid level on the growth of hybrid tilapia(T.autea ?* T.nilotica ? ).Experiment one: The effect of different dietary lipids on growth, body quality was studied . Hybrid tilapia , about 82.9g per fish , was divided into 6 groups in feeding trial for 35d, to study the ability of utilizing different dietary lipids . The experiment feeds were contained respectively with 3% of cotton oil i linseed oil, soybean oil, rapeseedoil, lard, beef tallow. Accordingly, the groups of tilapia were named group 1, 2, 3, 4, 5, 6.The results were followed:1 The growth result of hybrid tilapia:(l)The difference of daily growth rate was observed: group 2 was the highest, group 3 was the second, group 4 the third, group 1 the fourth, then group 6 , group 5.(2)Different feed efficiency was observed: group 2 was the highest, group 4 the second , group 3 the third, group 1 the fourth, then group 6 , group 5.2 Body quality:l)The biochemisty composition of the body was tested. (1) The body crude protein content (%) was "groups > group 4 > group 2 > group 6 > group 5 > group 1". (2) The body ether extract content (%) was "group 3 > group 4 > group 2 > group 5 > group I > group 6". (3 ) The moisture (67.76-70.48%). ash(2.80~3.56%), calcium (0.68-1.16%). phosphorus(0.36~0.43%) of the body were not significantly affected by dietary lipids. 2)Body fat property was significantly affected by dietary lipid. The body fat iodine value (mg/100g) tended to resemble that of dietary lipid.Experiment two: Using two-factor, three level orthogonal design, 270 hybrid tilapia with an average initial weight of 32.5g, were randomly divided into 9 groups in feeding trial for 64d to study the optimal EFA n-6/n-3 rate pattern and dietary lipid level , discussing a new way to evaluate and modulate dietary lipid nutrition. One factor is n-6/n-3EFA rate pattern : 22.25(patternA) , 15.45(Pattem B) , 9.04(PatternC). The other is dietary lipid level: 5% level, 3% level, 1% level. The growth, metabolism and body quality of hybrid tilapia were studied.The results were following:1 The growth of hybrid tilapia: (1) daily growth rate ( % ): Pattern A > Pattern B( P >0.05 ), and Pattern B > Pattern C ( P <0.05 ) ; 5% level >3% level > 1% level ( P >0.05 ) . (2) feed protein efficiency : Pattern A > Pattern B ( P >0.05) , and Pattern B > Pattern C ( P O.05 ) ; 5% level >3% level > 1% level ( P >0.05) .2 body quality determination: There is no significant difference in body moisture, ash, calcium and phosphorus content except of crude protein, ether extract and body index: (1) body crude protein content: Pattern A > Pattern B ( P<0.05) and Pattern B> Pattern C ( P>0.05 ); 5%level >3% level ( P >0.05)and 3% level > 1% level ( P<0.01 ). (2 )body ether extract content: Pattern A > Pattern B ( P <0.05 ) and Pattern B > Pattern C ( P >0.05 ); 3% level >5% level > 1 % level ( P >0.05 ) . ( 3 ) plumpness: Pattern A > Pattern B ( P >0.05 ) and Pattern B > Pattern C (P<0.05); 3%level>5%level .( P>0.05) and3%level> 1%level (PO.05). (4) internal organ index: Pattern C > Pattern A > Pattern B ( P >0.05) ; 3% level >5% level ( P >0.05) and 5% level > 1 % level ( P O.05 ) .3 Determination of metabolism: 1 ) The determination of transaminase correlating with amino acid metabolism: (1)the glutamic oxalacetic transaminase (GOT) of muscle was "Pattern B>Pattern OPattern A (P>0.05 ) ; 1% level>5% level (P<0.01),5% level>3% level". (2) the GOT of hepatopancreas was "Pattern OPattern A (P>0.05 ), Pattern A>Pattern B (P>0.05 ) and Pattern C>Pattern B( P<0.05); 1% level>5% leveK P<0.01), 5% level>3% leveK P>0.05)". 2) The determination of metabolite of fatty acid : ketone body was "Pattern OPattern B>PatternA (P<0.05) ; 5% level>l% level (P<0.05) , 1 % level>3% level (P>0.05) ".The results indicated that :1 Six kinds of dietary lipid affected the growth, feed efficiency and body quality of the hybrid tilapia. It is determined not only by n-6, n-3 fatty acids... |
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