饲料中添加外源酶对大黄鱼和鲈氮磷排泄的影响

EFFECTS OF EXOGENOUS ENZYMES ON AMMONIA NITROGEN AND SOLUBLE PHOSPHORUS EXCRETION IN LARGE YELLOW CROAKER( PSEUDOSCIAENA CROCEA) AND JAPANESE SEABASS(LATEOLABRAX JAPONICUS)

本研究以大黄鱼和鲈为实验对象,探讨饲料中添加植酸酶(PY)和非淀粉性多糖酶(WX和VP)对其氨氮和可溶性磷(PO43--P)排泄的影响。以含植物蛋白的饲料为基础饲料,分别向每千克饲料中添加200mg植酸酶(酶的活性为2500IU/g)、800mg WX(主要包括葡聚糖酶、戊聚糖酶和纤维素酶,各种酶的活性皆为50IU/g)、400mg VP(主要为木聚糖酶,酶的活性为1000IU/g)以及800mg WX+400mg VP配制出5种实验饲料。实验鱼在海水网箱中经过8周的摄食驯养后,转入室内水族箱中进行氮磷排泄测定实验。在水族箱中经2天的适应后,测定饥饿状态下氨氮及可溶性磷的排泄率。然后饱食投喂,并连续测定摄食后48h内鱼体氨氮和可溶性磷的排泄率。实验期间水温为26.5—32.5℃,盐度为32.5‰—36‰,溶氧在7 mg/L以上。实验结果表明,饥饿状态下实验鱼的氨氮和可溶性磷排泄不受实验饲料影响(p>0.05)。而在饱食条件下,实验饲料中添加非淀粉性多糖酶(WX、VP及WX+VP)显著降低了实验鱼的氨氮排泄率(p<0.05),而添加植酸酶组实验鱼的氨氮排泄率与对照组差异不显著。饲料处理对实验鱼可溶性磷的排泄率的影响不显著(p>0.05),但添加植酸酶组实验鱼的可溶性磷排泄率有增加的趋势。

An experiment was conducted to evaluate the effects of dietary phytase （PY） and non-starch polysaccharide enzyme （WX and VP） on ammonia nitrogen and soluble phosphorus excretion in large yellow croaker （Pseudosciaena crocea ） and Japanese seabass （ Lateolabrax japonicus）, respectively. Using soybean meal, rapeseed meal, peanut meal, fish meal and meat and bone meal as protein sources, fish oil and soybean oil as lipid sources, lysine, methionine and valine as supplements simulated the essential amino acid pattern of fish meal, five isonitrogenous and isoenergetic experimental diets were formulated to contain 0, 200mg/kg phytase （2500 IU per gram）, 800mg/kg WX （mainly including glucanase, pentosanase and cellulosase, each with 50 IU per gram）, 400mg/kg VP （mainly including xylanase, 1000 IU per gram）, and the combination of 800 mg/kg WX and 400mg/kg VP, respectively. Each diet was randomly assigned to triplicate groups of fish, and each group was stocked with 180 large yellow croaker （ initial body weight, （ 1.88 ± 0.02） g） or 60 Japanese seabass [ initial body weight, （6.28 ± 0.1 ） g ] . Fish were fed twice daily （06：30 and 16：30） to satiation for 8 weeks. During the experimental period, the water temperature fluctuated from 26.5 ℃ to 32.5 ℃, salinity from 32‰ to 36‰ and dissolved oxygen was approximately 7mg/L. After feeding for 8 weeks in sea cages with experimental diets, fish from each cage （3 fishes per cage） were transferred into indoor tank （20L） to determine ammonia nitrogen and soluble phosphorus excretion rates in starvation and satiation condition. Each tank stocked with 1 large yellow croaker （12.48 ± 1.02） g or 1 Japanese seabass （54.87 ± 2.34） g. The ammonia nitrogen was determined by the sodium hypobromite oxidation method. The soluble phosphorus was determined by phosphorus molybdenum blue method. The resuits showed that ammonia nitrogen and soluble phosphorus excretion rates of fish in starvation condition were not affected by the experimental diets （p 〉 0.05 ）. However, the ammonia nitrogen excretion rates in satiation condition were significantly lower in fish fed with diets supplemented with the combination of WX and VP, WX or VP than that fed with basal diet and phytase supplemented diet （p 〈 0.05）, and ammonia nitrogen excretion rates in fish fed with basal diet and phytase supplemented diet were not significantly different. Soluble phosphorus excretion rates of fish fed with different experimental diets were not significantly different （p 〉 0.05）, but there was an upward trend of soluble phosphorus excretion rate in fish fed with phytase supplemented diet. These findings in the present study suggested that supplementation of 200 mg phytase per kilogram diet might degrade the dietary phytate and increase availabile phosphorus absorbability, but not significant effects on ammonia nitrogen excretion rates of large yellow croaker and Japanese seabass. The non-starch polysaccharide enzymes （400 mg VP, 800 mg WX, or the combination of 800 mg WX and 400 mg VP per kilogram diet） were effective to degrade the anti-nutritional effect of non-starch polysaccharide and decrease ammonia nitrogen excretion rates of large yellow croaker and Japanese seabass, but not significant effects on soluble phosphorus excretion rates of experimental fish.