Glycerol is an inexpensive source of dietary energy, although its inclusion in compound feeds has been barely investigated in fish. The effects of dietary refined glycerol inclusion on growth performance, nitrogen and energy balance, as well as its digestibility and intestinal digestive enzyme activities was studied in rainbow trout. Fish (initial BW 20.2 ± 0.1 g, mean ± SE) were divided into nine tanks (1.66 kg m⁻³), each one assigned to the experimental diets, in triplicates. Fish were fed twice a day to apparent satiation for 60 days three diets including 0, 25, or 50 g kg⁻¹ of refined glycerol (G0, G25, and G50, respectively) with similar digestible protein to energy ratios (22 mg kJ⁻¹). A digestibility trial was conducted in parallel to the growth trial by using a Choubert System to collect feces, in triplicates. Refined glycerol was well digested (ADC_glycerol > 99.7%) when included up to 50 g kg⁻¹. Specific growth rate (SGR) decreased as glycerol inclusion levels increased in the diet (P = 0.029). Feed intake was enhanced with increasing dietary inclusion levels of glycerol (P = 0.013). The feed efficiency decreased linearly as the glycerol inclusion levels increased in the diet, reflected in a higher FCR ratio, particularly in the G50 group compared to the G0 or G25 groups (1.04 ± 0.02, 0.90 ± 0.02 and 0.91 ± 0.02, respectively). Total ammonia nitrogen excretion rate (TAN_ER) was measured in trout at the end of the growth trial, displaying increased values with higher dietary glycerol inclusion levels (P < 0.001). As a result, trout fed G25 or G50 diets displayed an increased energy intake, which was not reflected in a reduction of the nitrogen excretion rate. Contrary to expected, glycerol had a negative effect on nitrogen efficiency, indicating that dietary inclusion of this compound does not spare the use of proteins as a metabolic fuel. In addition, amylase, but not proteases and lipase, was altered in the intestine of trout by refined glycerol inclusion, as this digestive enzyme activity increased 6 h post-feeding in trout fed G25 and G50 diets. In conclusion, dietary refined glycerol inclusion on rainbow trout was not reflected in beneficial effects on fish performance or in the quantity of nitrogen waste products excreted to the environment by this carnivorous species.

甘油是一种廉价的饮食能量来源，尽管在鱼类中几乎没有研究将其包含在复合饲料中。在虹鳟鱼中研究了日粮精制甘油含量对生长性能，氮和能量平衡及其消化率和肠内消化酶活性的影响。将鱼（初始体重20.2±0.1 g，平均值±SE）分成9个槽（1.66 kg m ^-3），每槽一式三份。喂食每天两次至表观饱食60天三种饮食包括0，25％，或50克千克^-1精制甘油（G0，G25，和G50分别）具有类似的可消化蛋白质能量比（22毫克千焦^{- 1个}）。通过使用Choubert系统一式三份收集粪便，与生长试验同时进行了消化率试验。 当包含至多50 g kg ^-1时，精制甘油被很好地消化（ADC_甘油> 99.7％）。随着饲料中甘油含量的增加，比生长速率（SGR）降低（P  = 0.029）。饮食中甘油的添加水平增加，饲料摄入量增加（P  = 0.013）。饲料效率随着日粮中甘油含量的增加而线性降低，这反映在较高的FCR比上，尤其是与G0或G25组相比，G50组（分别为1.04±0.02、0.90±0.02和0.91±0.02）。总氨氮排泄率（TAN _ER）是在生长试验结束时在鳟鱼中测得的，显示出较高的饮食甘油含量（P <0.001）。结果，用G25或G50饮食喂养的鳟鱼显示出增加的能量摄入，这并未反映在氮排泄率的降低上。与预期相反，甘油对氮效率有负面影响，表明在饮食中加入该化合物并不能避免使用蛋白质作为代谢燃料。此外，通过精制甘油的加入，在鳟鱼的肠道中淀粉酶（而不是蛋白酶和脂肪酶）发生了变化，因为在饲喂鳟鱼的G25和G50日粮中，这种消化酶活性在饲喂6小时后会增加。总之，在虹鳟鱼中添加精制甘油的饮食并未反映在对鱼类生产性能的有益影响或该食肉动物排泄到环境中的氮废物的数量上。