Characterization of digestive physiology in Pacific bluefin tuna Thunnus orientalis juveniles fed a raw fish feed and a commercial diet
Characterization of digestive physiology in Pacific bluefin tuna Thunnus orientalis juveniles fed a raw fish feed and a commercial diet
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DOI：
10.1016/j.aquaculture.2021.736562
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发表时间：
2021-02
期刊：
影响因子：
4.5
通讯作者：
K. Murashita;H. Hashimoto;Toshinori Takashi;Takeshi Eba;Kazunori Kumon;H. Matsunari;Satoshi Soma;H. Oku;H. Furuita;Hazuki Yoshinaga;Takeshi Yamamoto
中科院分区：
文献类型：
--
作者：
K. Murashita;H. Hashimoto;Toshinori Takashi;Takeshi Eba;Kazunori Kumon;H. Matsunari;Satoshi Soma;H. Oku;H. Furuita;Hazuki Yoshinaga;Takeshi Yamamoto
本研究检测了人工养殖太平洋蓝鳍金枪鱼幼鱼关键消化酶的生化特性，揭示了长期（225天）和短期（对饵料的反应）饲喂商业颗粒饲料和生鱼幼鱼的消化生理细节。研究了蓝鳍金枪鱼幼鱼胃蛋白酶、胰蛋白酶、糜凝胰蛋白酶、脂肪酶和淀粉酶等关键消化酶的pH值和热谱，发现其特征与先前报道的幼鱼和成年金枪鱼不同。长期饲喂（225 d）商品饲粮显著提高了胃和幽门盲肠的大小以及消化酶的储存/合成水平。在商业饲料喂养的幼鱼中也发现了胆囊收缩素（cck）及其受体（cck1r）的基因表达水平高度增加，这表明cck可能参与了本研究中看到的胃肠道肥大和消化增强。在短期试验（对饵料的反应）中，饲料喂养的幼鱼胃排空速度更快，肠道内容物pH值更高，消化酶的储存/合成增加，而酶的分泌与饲料喂养的幼鱼相似。这表明蓝鳍金枪鱼幼鱼的消化系统在形态和生理上适应了人工饲料，但这种适应不足以获得与金枪鱼喂食生鱼饲料相当的性能。消化酶生化特性及人工饲料对消化生理的影响可作为改善金枪鱼幼鱼饲料组成、摄食比例和频率等饲养策略的良好指标。
This study examined the biochemical characteristics of key digestive enzymes in artificially produced Pacific bluefin tuna juveniles and revealed details of the digestive physiology of juveniles fed a commercial pellet diet and raw fish over long-term (225 days) and short-term (response to feeding) periods. pH and thermal profiles of key digestive enzymes of pepsin, trypsin, chymotrypsin, lipase and amylase were examined in juvenile bluefin tuna and the characteristics differed from those previously reported for larval and adult tuna. Long-term feeding (225 days) of the commercial diet markedly increased stomach and pyloric caeca size as well as storage/synthesis levels of the digestive enzymes. Highly increased gene expression levels of cholecystokinin (cck) and its receptor (cck1r) were also found in juveniles fed the commercial diet, suggestingcckmight be involved in the gastrointestinal hypertrophy and digestion enhancement seen in the present study. In the short-term experiment (response to feeding), juveniles fed the commercial diet displayed faster gastric emptying, higher pH in the intestinal content and increased digestive enzymes storage/synthesis whereas the enzymes secretion was similar with those of juveniles fed raw fish. These indicate that juvenile bluefin tuna morphologically and physiologically adapted their digestive system to the artificial diet, however the adaptation was not sufficient to obtain a comparable performance as tuna fed raw fish feed. Biochemical characteristics of the digestive enzymes and the observed effects of artificial diet on digestive physiology could be good indicators to improve feeding strategies such as diet composition, feeding ration and frequency in juvenile tuna.