飼料中添加不同來源及比例之脂質在不同溫度下對紅色吳郭魚成長及魚體脂肪酸組成之影響

Abstract

吳郭魚為世界主要的養殖魚種之一，2007年世界養殖產量約為兩百五十多萬噸，故其對於飼料之需求相當大，一般而言吳郭魚對於植物性蛋白質利用性及碳水化合物利用性不差，但對於脂質種類及其利用效率的研究方面並不是很多。本實驗主要利用烏賊油、牛油以及大豆油以不同比例之組合(0%、2%、3%或5%)配置成額外添加5%脂質於紅色吳郭魚的飼料原料中來探討不同脂質來源、比例及不同溫度下對其成長、魚體脂肪酸組成及必需脂肪酸需求的影響。 實驗一為原料中額外添加5%之脂質且利用烏賊油、牛油以及大豆油各別以0%、2%、3%或5%單一添加或混合添加配製成九組飼料，並加上一組完全不額外添加油脂之組別，在平均溫度為22±2℃環境下對體形大小為1.21±0.04g之紅色吳郭魚進行十週的飼養。結果發現，成長方面以添加5%烏賊油組較大豆油:烏賊油=2:3及不添加油脂組好，且出現顯著性差異(p＜0.05)，其他各組間則無顯著差異存在(p＞0.05)；全魚體脂肪酸組成及肝臟非極性脂肪之脂肪酸組成則約反映出飼料中之脂肪酸組成；肝臟中極性脂質之脂肪酸組成方面，經由20:3n-9/ 20:4n-6與20:3n-9 /22:6n-3之比值中則發現添加烏賊油5%、牛油5%、牛油:大豆油=2:3及大豆油:烏賊油=3:2四組中可滿足紅色吳郭魚之n-6及n-3脂肪酸需求。 實驗二則分別利用烏賊油、牛油、大豆油5%以及大豆油:烏賊油=3:2四組飼料在21±1℃的低溫條件及26±1℃的高溫條件對體形大小為0.74±0.03g之紅色吳郭魚進行八週的飼養。結果以高溫組別成長效果較低溫組別佳，且高溫組別中牛油5%之成長較烏賊油5%好，出現顯著性差異(p＜0.05)而其他各組間則無顯著差異(p＞0.05)，低溫組別中則以5%大豆油組較5%牛油及大豆油:烏賊油=3:2組好，有顯著性差異(p＜0.05)而其餘各組則無顯著差異(p＞0.05)；全魚體之脂肪酸組成及肝臟非極性脂肪之脂肪酸組成在各組之間約反映出飼料之脂肪酸組成；肝臟中極性脂質之脂肪酸組成方面則發現在高溫及低溫環境下大豆油:烏賊油=3:2組別沒有滿足其n-6脂肪酸需求。

Tilapia is one of the main cultured fish in the world and the aquacultured production in 2007 was about 2,500,000 tons. Therefore, the demand of feed in tilapia aquaculture is enormous. In General, tilapia could use plant protein sources and carbohydrate efficiently. So the lipid sources and its efficiency may cause important effect for cost of feed. In present study, red tilapia diets were supplemented with additional 5% lipid from different proportion (0%, 2%, 3% or 5%) of either squid oil, beef tallow or soybean oil to investigate the influence of growth performance, body fatty acid composition and essential fatty acid demand under different temperarure. In experiment one, nine diets were supplemented with additional 5% lipid from different proportion (0%, 2%, 3% or 5%) of either squid oil, beef tallow, soybean oil and one diet was not supplemented with any additional lipid (Ctrl). Red tilapia fingerlings (1.21±0.04g) were fed in average 22±2℃ condition for ten weeks. After feeding trial, growth performance was significantly higher (p＜0.05) in red tilapia fed with S5 (squid oil 5%) than in fish fed SB2S3 (soybean oil: squid oil=2:3) and Ctrl. Other groups were not significantly different (p＞0.05) compared with each other. Fatty acid composition in whole body and non-polar lipid fraction from liver reflected the composition of diet. And red tilapia fed with S5, T5 (beef tallow 5%), T2SB3 (beef tallow: soybean oil=2:3) and SB3S2 (soybean oil: squid oil=3:2) were satisfied n-6 series and n-3 series fatty acid requirement by calculating the ratio of 20:3n-9/20:4n-6 and 20:3n-9/22:6n-3 in polar fraction from liver. In experiment two, three diets were supplemented with additional 5% lipid from either squid oil, beef tallow and soybean oil and one diet was supplemented with 3% soybean oil and 2% squid oil. Red tilapia fingerlings (0.74±0.03g) were fed in 20℃ (low temperature, LT) and 27℃ ( high temperature, HT) condition for eight weeks. After feeding trial, growth performance was significantly higher (p＜0.05) in HT groups than in LT groups. In HT groups, growth was significantly higher (p＜0.05) in T5 than in S5 and other treatments were not significantly different (p＞0.05) compared with each other. In LT groups, growth was significantly higher (p＜0.05) in SB5 (soybean oil 5%) than in S5 and SB3S2 but other treatments were not significantly different (p＞0.05) compared with each other. Fatty acid composition in whole body and non-polar lipid fraction from liver reflected the composition of diet. Moreover, red tilapia fed with SB3S2 was not satisfied n-6 series fatty acid requirement both in LT and HT conditions.