饲用溶菌酶对吉富罗非鱼消化道组织结构和营养物质消化吸收的影响

Effects of Dietary Lysozyme on the Digestive Tract Structure and Nutrient Digestibility of GIFT Tilapia (Oreochromis niloticus)

中文关键词: 吉富罗非鱼  溶菌酶  消化吸收率  消化酶  肝肠组织形态

英文关键词: GIFT tilapia  Lysozyme  Nutrient digestibility  Digestive enzyme  Digestive tract morphology

中文摘要:

      为了解饲用溶菌酶对吉富罗非鱼(Oreochromis niloticus)消化道组织结构发育和营养物质利用的影响，本研究设计5种饲料溶菌酶添加水平：18 mg/kg (L18)、36 mg/kg (L36)、54 mg/kg (L54)、72 mg/kg (L72)和90 mg/kg (L90)，以不添加溶菌酶的饲料(L0)为对照，进行为期60 d的饲养。结果显示，饲料中添加溶菌酶对吉富罗非鱼肝脏和胃肠道消化酶活性产生了不同程度的影响。L36、L54和L72组的胃、前肠和中肠蛋白酶活性显著高于对照组(P<0.05)，肝脏、前肠脂肪酶活性在L54和L72组均显著高于对照组(P<0.05)，淀粉酶活性在除前肠、中肠外的L72和L90组显著高于对照组(P<0.05)。L36、L54和L72组鱼的肠道不同部位肠绒毛密度、高度和宽度较对照组显著提高，在肌层厚度上，溶菌酶添加组在前肠和后肠部位有下降趋势，L18、L36和L90组显著低于对照组(P<0.05)，而在中肠部位，肌层厚度随添加水平升高而呈先升后降的变化趋势，L36、L54和L72组在数值上高于对照组，但无显著性差异(P>0.05)；杯状细胞数量在L54和L72组均显著高于对照组(P<0.05)。肝脏切片图显示，L36和L54组肝细胞排列整齐、形状饱满，相较于对照组更致密，但高剂量添加组的肝脏健康程度有下降趋势。消化吸收率方面，在饲养Ⅰ期和Ⅱ期，L36和L54组对粗蛋白的表观消化率显著高于对照组，到饲养Ⅲ期和Ⅳ期，L36~L90组对干物质、粗蛋白和粗脂肪的消化吸收率均有显著提高(P<0.05)。研究表明，在本实验条件下，36、54 mg/kg溶菌酶添加水平具有最稳定的作用效果，吉富罗非鱼通过肝肠发育和消化酶活性的提高来促进对饲料干物质、粗蛋白和粗脂肪的消化吸收。

英文摘要:

      To investigate the effects of lysozyme as a green feed additive on the development of the digestive tract and digestive utilization of nutrients in GIFT tilapia, a 60-day feeding trial was conducted with graded levels of dietary lysozyme (0, 18, 36, 54, 72, and 90 mg/kg, marked as L0, L18, L36, L54, L72, and L90 respectively). The results were as follows: The fish had a different feedback response on the digestive enzyme activity in the liver and the gastrointestinal tract among groups; the protease activity in the stomach, and the anterior and middle intestine of L36~L72 groups was significantly higher than that of the control group (P<0.05); the lipase activity in the liver and the anterior intestine of the L54 and L72 groups was significantly higher than that of the control group (P<0.05); and the amylase activity in the digestive tracts (anterior and middle intestine excluded) of the L72 and L90 groups was significantly higher than that of the control group (P<0.05). The intestinal morphology showed that the values of villus density, villus height, and villus width of different intestinal parts in L36~L72 groups were higher than those of the control group, while the muscular thickness of the anterior and distal intestine was reduced in dietary lysozyme groups. The thickness of the middle intestines of the L18, L36, and L90 groups was significantly lower than that of the control group (P<0.05), and there was a firstly increased and then decrease tendency. The thickness of the middle intestines of L36~L72 groups were all higher than the control group with no significant difference (P>0.05). The goblet cell numbers were more in the L54 and L72 groups than in the control group (P<0.05). The liver morphology showed that the liver cells were more voluptuous and denser in the L36 and L54 groups than in the control group, while worse health condition was found in the L90 group. With regards to apparent nutrient digestibility, the crude protein digestibility was significantly higher in the L36 and L540 groups than in the control group in periods I and Ⅱ (P<0.05), and in periods Ⅲ and Ⅳ. The digestibility of dry matter, crude protein, and crude lipid were significantly higher in L36~L90 groups than in the control group (P<0.05). The results above indicated that 36 and 54 mg/kg dietary lysozyme had the most stable efficacy, which could improve GIFT tilapia dry matter, crude protein, and crude lipid digestibility by promoting liver and intestine development and digestive enzyme activity.