大口黑鲈配合饲料中3种动物蛋白源的不同添加比例对其生长性能、肠道健康及蛋白质代谢的影响

Effects of dietary animal protein source composition on the growth performance, intestinal health, and protein metabolism of largemouth bass (Micropterus salmoides)

中文关键词: 大口黑鲈  动物蛋白源  生长性能  蛋白质合成  肠道健康

英文关键词: Micropterus salmoides  Animal protein source  Growth performance  Protein synthesis  Intestinal health

中文摘要:

      目前，大口黑鲈(Micropterus salmoides)配合饲料对鱼粉的依赖性大，而鱼粉价格不断上涨，导致其饲料成本居高不下，严重制约了其养殖业的健康发展。为降低饲料成本，本研究以鱼粉、鸡肉粉和猪肉粉为饲料动物蛋白源，制作7种配合饲料(D1~D7)，其鱼粉/鸡肉粉/猪肉粉的添加百分比分别为45.0/22.6/0、37.1/22.6/8.0、28.8/22.6/16.0、45.0/14.5/8.0、45.0/5.3/16.0、41.6/18.0/8.0和37.0/13.8/16.0。采用上述饲料投喂大口黑鲈幼鱼(初始体重约为55 g) 60 d，评估饲料动物蛋白源组合对鱼生长性能、组织生化指标、肌肉质构特性以及肝脏蛋白质代谢和肠道炎性因子相关基因表达的影响。结果显示，相比于其他饲料投喂组，D3组鱼的终末体重、增重率、特定生长率显著提高，饲料系数显著降低(P<0.05)；D3组全鱼粗蛋白质显著高于D5组，其粗脂肪水平显著低于D4和D6组(P<0.05)。在组织生理生化指标方面，D3组鱼血清总氨基酸含量显著高于D1和D4组(P<0.05)，而其谷草转氨酶活性显著低于D5组(P<0.05)；D3组鱼肝脏总蛋白含量显著高于D7组(P<0.05)。在肌肉品质方面，D3组肌肉硬度和胶着性以及咀嚼性分别显著低于D4组和D6组(P<0.05)。此外，D3组肠抗炎基因il-10，肝脏蛋白质合成基因tor、s6k1、akt、pi3k mRNA表达水平上调，显著高于D7组(P<0.05)；而肠促炎因子il-1β、il-6和肝脏翻译抑制因子4ebp-1 mRNA表达水平下调，显著低于D1组(P<0.05)。上述结果表明，饲料中添加28.8%鱼粉、16.0%猪肉粉和22.6%鸡肉粉对大口黑鲈的促生长效果最优，且有利于提高肝脏蛋白质合成，维护肠道健康。研究结果可为降低大口黑鲈配合饲料对鱼粉的依赖提供技术支撑。

英文摘要:

      Terrestrial animal protein sources contain less antinutritional factors, high protein content, and functional factors, which are beneficial to fish health. Among them, poultry byproduct meal (containing 65%–73% protein rich in vitamins) and porcine meat meal (containing 45%–60% protein and high contents of proline and glycine) are the most widely used meals in aquatic compound feeds, and are important fish meal replacement sources. As a carnivorous fish species, largemouth bass (Micropterus salmoides) is highly dependent on dietary fish meal, and the level of fish meal added in its commercial feeds is up to 50%. However, the rising price of fish meal increases the farming cost of M. salmoides. Therefore, it is necessary to identify a suitable alternative protein source to reduce the amount of dietary fish meal and the feed cost. Therefore, seven compound feeds (D1–D7) were prepared in this study. The added ratios of fish meal/poultry byproduct meal/porcine meat meal were as follows: 45.0/22.6/0, 37.1/22.6/8.0, 28.8/22.6/16.0, 45.0/14.5/8.0, 45.0/5.3/16.0, 41.6/18.0/8.0, and 37.0/13.8/16.0. Juvenile M. salmoides (initial body weight ~55 g) were fed the above diets for 60 days with five replicates in each group. The effects of the animal protein source combination on the growth performance, tissue biochemical indices, muscle texture characteristics, liver protein metabolism, and intestinal inflammatory factor-related gene expression were evaluated. The water temperature during the feeding trial was 27.4–32.3 ℃ and the ammonia nitrogen concentration was 0.1–0.2 mg/L. After the feeding experiment, three fish were randomly selected from each cage to collect the serum, liver, intestinal tract, muscle, and other samples, which were then stored at –80 ℃. In addition, three fish were randomly selected from each cage to determine their morphological indices. At the same time, two fish were selected from each cage to determine the muscle texture characteristics and the whole fish proximate composition. Physiological and biochemical indices of serum and liver tissues, albumin, urea nitrogen (BUN), total amino acid (T-AA), alanine aminotransferase (ALT), aspartate aminotransferase, total protein (TP), and blood ammonia (SA) levels), were determined using commercial kits, and the texture characteristics of muscle were determined by using a texture analyzer. The moisture, crude fat, crude protein, and ash contents of whole fish and muscle were determined by atmospheric drying, Soxhlet extraction, Kjeldahl nitrogen determination, and Muffle furnace incineration, respectively. Real-time quantitative PCR was used to determine the expression levels of genes related to liver protein metabolism and the intestinal inflammatory response. All test data were expressed as the mean±standard error, and multiple comparisons were made by the Tukey test, with P<0.05 indicating a significant difference. The results showed that, compared with other groups, the final body weight, weight gain rate, and specific growth rate of fish in the D3 group were significantly higher, and the feed conversion ratio was significantly lower (P<0.05). There were no significant differences in the condition factor, hepatosomatic index, viscerosomatic index, and survival rate among all groups (P>0.05). The whole-body crude protein content in the D3 group was significantly higher than that in the D1 group, and the crude lipid level in the D3 group was significantly lower than that in the D6 group (P<0.05). In terms of tissue physiological and biochemical indices, there were no significant differences in the activities of BUN and ALT in serum, SA content, and ALT activity in the liver among all groups (P>0.05). The serum T-AA content of fish in the D3 group was significantly higher than that in the D1 and D4 groups (P < 0.05), but the AST activity in the D3 group was significantly lower than that in the D5 group (P<0.05). The liver TP content in the D3 group was significantly higher than that in the D7 group (P<0.05). There were no significant differences in the serum TP and liver ALT contents in the D3 group compared with those of the other groups (P>0.05). In terms of muscle quality, the muscle hardness, adhesion, and mastication in the D3 group were significantly lower than those in the D4 and D6 groups, respectively (P<0.05). There were no significant differences in the muscle adhesiveness, elasticity, cohesiveness, moisture, crude protein content, crude lipid content, and ash content among all groups (P>0.05). In addition, the mRNA expression levels of intestinal il-10 and liver tor, s6k1, akt, and pi3k in the D3 group were upregulated, and were significantly higher than those in the D7 group (P<0.05). The mRNA expression levels of il-1β and il-6 in the intestines and 4ebp-1 in the liver of the D3 group were significantly lower than those of the D1 group (P<0.05). These results indicated that combined use of 28.8% fish meal, 16.0% porcine meat meal, and 22.6% poultry byproduct meal had the best growth promotion effect on M. salmoides, and was able to improve liver protein synthesis and maintain intestinal health. The results of this study provided technical support for reducing the dependence of M. salmoides compound feed on fish meal.