博士 / 國立海洋大學 / 食品科學系 / 90 / Comparison on growth and digestive protease activities of eel (Anguilla japonica) fed with float and paste feed
Abstract
Juvenile eel (Anguilla japonica) 20 ±1.5 g were cultured in cement ponds （2.5×1×1 m×m×m） for 14 months at a density of 10 eel/m3. The weight gain was measured, and the daily growth rate (D.G.R) was calculated at 5 stages according to the commercial practice. No significant difference (p ＞0.05) on weight gain was observed between eel fed paste feed and those fed float feed. By feeding float diet, the D.G.R. of eel decreased from 2.2 % to 0.82 %, as the eel grew from stage 1 to stage 5, and the feed conversion ratio (F.C.R) averaged 1.5 to 1.6. For eel fed paste feed, the D.G.R reduced from 2.5 % to 0.84 % with a F.C.R being 1.6 to 1.7. The standard deviation (s.d.) of weight for eel fed paste feed was 60 % higher than those fed float feed at stage 1 and 2. The s.d. increased with age and weight to being two times of the latter at stage 3 to 5. Size variability was more pronounced in eel fed on paste feed than in those fed float feed.
Two pepsins, designated P I and P II were isolated from the stomach of juvenile and adult eel. The optimal pH of P I was 1.5 for juvenile (50 ±5 g) and 2.0 for adult eel (150 ±10 g), while that of P II was 3.5 for both eel. P I in juvenile eel was 1.5~2.0 times active than that in adult eel. Salt at 0.14~0.21 mM activated P I activity to 2 times of that without the presence of salt. P II activity was not affected by salt.
Trypsin at opt pH 8.0 and chymotrypsin at opt pH 7.0 seemed to correlate with the quantity of digesta in the organ while pepsin activity bore no correlation with digesta. The profile of post-feeding digestive proteases was different between eel fed float feed and fed paste form as a result of its susceptibility for proteases to diffuse into the feed digesta. The observations were carried during a 14 month feeding trial. The only difference resulted between the float diet and the paste diet fed to eel was the 24 h-profile of the post-feeding digestive proteases activated in the tissues and in the digesta of the gastrointestinal tract. It seemed that the susceptibility of the ingested feed to be broken down into particles in smaller sizes, ie 0.1 mm dia, for proteases readily diffusive into the digesta was a determinant of the in-vivo digestion in eel.
In the intestine extract of eel, trypsin activity increased clearly after enteropeptidase being added to activate the zymogens sampled 24 h after fed , the activation increased with reaction time from 30 min to 75 min. Without the addition, trypsinogen was activated slowly. Enteropeptidase also activated chymotrypsinogen to chymotrypsin either 8 or 24 h after feeding. The activity of carboxypeptidase A was low (<0.07 uint /mg protein) , having two activity peaks at pH 4.0 and 7.0. At pH 7.0 , carboxypeptidase A activity was increased with time from 8 to 14 h after fed. At pH 4.0 maximal activity was observed at 8 h. Carboxpeptidase B, also having two activity peaks at pH 4.0 and 8.0, showed higher activities than carboxypeptidase A.
In-vitro digestion of feeds using stomach extract (pH 3.5) and intestine extract (pH 7.0) from eel weighed 150 ±10 g , was carried for 3 to 24 h consecutively simulating the in-vivo digestion in eel. After in vitro digestion, the basic and aromatic amino acids in paste feed digest were 2 times of those in the float feed digest. Digestion by intestine extract for 3 h , the aromatic amino acids in paste feed digest were 66% of those in the float feed digest. After digestion by stomach and intestine extract for 6 h ,the aromatic amino acids increased at a rate of 9.9 μmole/ g protein/ h in float feed digest and 2.1 μmole/ g protein / h in paste feed digest. Prolonged digestion by intestine extract for 3 to 11 h，the aromatic amino acids increased at a rate of 5.2 μmole/ g protein /h in float feed digest and 7.5 μmole/ g protein / h in paste feed digest, then the digestion rate slowed down. The basic amino acids after intestine extract continued to digest for 3 to 8 h increased at a rate of 21.3 μmole/ g protein/ h in float feed digest and 23.3 μmole/ g protein/ h in paste feed digest, then reached stable stage during 8 to 24 h after fed.
Blood plasma of eel sampled at 3 to 14 h after feeding with float or paste feed showed maximal values in total amino acids and total essential amino acids. The total and acidic amino acids were higher in float feed digest (p＜0.05), while the essential and basic amino acids were higher in paste feed digest (p＜0.05). No significant difference (p＞0.05) was found on the aromatic amino acid content of in-vitro digests of the two feeds. This observation coincided with the fact that no difference was found in weight gain. Blood plasma of eel sampled at 14 h after feeding with float feed showed significantly higher contents of total amino acids, essential amino acids and aromatic amino acids than those of eel fed paste feed, while lysine content in the former was significantly lower than that in the latter. No correlation was found between plasma amino acids 14 h after fed and weight gain. Therefore, the aromatic amino acid content in the in-vitro digest of feeds, indicating the availability of these aromatic amino acids can serve as an indicator of feed for predicting eel growth and FCR.
| Identifer | oai:union.ndltd.org:TW/090NTOU0253002 |
| Date | January 2002 |
| Creators | Shieh-Tsung Chiu, 邱謝聰 |
| Contributors | Bonnie Sun Pan, 孫寶年 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 95 |
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