A 10‐week feeding experiment was conducted to determine the optimum dietary protein requirement of juvenile obscure puffer (Takifugu obscurus). Six isoenergetic (20 MJ kg?1 gross energy) diets were formulated to contain graded levels of 34%, 38%, 42%, 46%, 50% or 54% crude protein (as dry matter basis). The results showed final body weight, weight gain and specific growth rate (SGR) increased significantly with increasing protein levels up to 42% and then decreased thereafer. Second‐order polynomial regression analysis (y = ?0.0024x2 + 0.1788x ? 1.3196, R2 = 0.9032) indicated a maximum SGR at protein level of 37%. Feed conversion ratio (FCR) decreased with increasing levels of dietary protein up to 42% and increased thereafter. Second‐order polynomial regression analysis (y = 0.0054x2 ? 0.4351x + 10.391, R2 = 0.753) indicated a minimum FCR at protein level of 40%. Protein efficiency ratio (PER) of fish fed the 34%, 38% and 42% diets was significantly higher than that of fish fed the 46%, 50% and 54% diets, and broken‐line analysis indicated PER tended to decrease when dietary protein level was higher than 40%. Generally, whole body lipid content, total cholesterol, low‐density lipoprotein cholesterol and triacylglycerol decreased with increasing levels of dietary protein. Fish fed the 42% protein diet showed the highest essential amino acids (histidine, isoleucine, leucine, lysine and threonine) and non‐essential amino acids (aspartic acid and glutamic acid) in muscle. Based on the second‐degree polynomial regression analysis of SGR and FCR and broken‐line analysis of PER, the optimal dietary protein level of obscure puffer is estimated to be between 37% and 40% (% as dry matter basis). 相似文献
Waterless live fish transportation is an alternative and promising transport strategy, which may reduce shipping costs, increase stocking density and improve survival of some species. Spotted sea bass is one of the most economically important marine fish in China. However, waterless transportation has not yet been studied on spotted sea bass. To explore the possibility of waterless transportation of spotted sea bass and its sublethal stress responses, the survival rate and dynamics of blood biochemical parameters were evaluated in the present study by preserving it under no water, less water and water (control) conditions for 9 hr. The serum biochemical parameters including total protein, cortisol, glucose, lactate, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total carbon dioxide (TCO2), creatinine, blood urea nitrogen (BUN), ammonia, superoxide dismutase (SOD) activity and malonaldehyde (MDA) were investigated. Results showed that the survival rates of fish in all groups gradually declined with time increasing. At the end of transportation, the survival rates in the control group, less‐water group and no‐water group decreased to 49.11%, 15.60% and 23.96% respectively. Significant changes were observed in several selected serum biochemical parameters, including glucose, lactate, ALT, TCO2, BUN and ammonia during simulated waterless transportation, which might negatively affect the physiological homeostasis of fish, leading to the high mortality in present study. In general, waterless transportation of spotted sea bass was possible, but it might be rather suitable for short time than long time. 相似文献
Two independent field experiments (2017 and 2019) were conducted to evaluate the effects of plant growth promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF; AMF1: Rhizophagus irregularis strain and AMF2: AMF consortium) and compost (Comp) in comparison to chemical NPK fertilizers on growth and yield of lettuce plants and soil properties. The biofertilizers-biostimulants were applied alone or in combinations and increased significantly the lettuce dry weight (DW), number of leaves, and yield compared to the control. In the first experiment, the highest plant DW was obtained by NPK, PGPR?+?AMF2?+?Comp and PGPR treatments recording an increase of 109, 109, and 95%, respectively, compared to the control plants. In the second experiment the highest plant DW was obtained by the NPK (77%), followed by Comp and PGPR?+?AMF1?+?Comp treatments increasing the plant DW by 52 and 51%, respectively, compared to the control. Concerning to lettuce yield, in the first experiment, the highest yields were obtained by NPK, PGPR?+?AMF2, PGPR?+?AMF1?+?Comp, PGPR, AMF2?+?Comp, AMF1?+?Comp and AMF2 treatments recording an enhancement of 68, 64, 63, 58, 57, 57, and 55%, respectively. In the second experiment, the application of NPK based fertilizers resulted in the highest yield (77%), followed by PGPR?+?AMF1?+?Comp, PGPR?+?AMF2?+?Comp, AMF1?+?Comp, and AMF2?+?Comp treatments, increasing the yield by 61, 61, 54, and 55%, respectively, compared to the control. Concerning the soil organic matter (OM), the applied treatments had significantly increased the amount of the OM compared to the control. The highest amounts of OM were obtained by the PGPR?+?AMF2?+?Comp treatment in the first experiment and the PGPR?+?AMF1?+?Comp treatment in the second experiment. The available phosphorus (P) was significantly increased by the application of all treatments. The highest records were obtained by the application of Comp, PGPR?+?AMF1 and PGPR?+?AMF1?+?Comp treatment after the first experiment. In the second experiment, the highest amount of P was obtained by PGPR?+?AMF2?+?Comp treatment. Application of biofertilizers-biostimulants in combination proved to be beneficial for the improvement of the tested culture yield.
