Performance of pacu juveniles fed diets supplemented with L-carnitine

Abstract: The objective of this work was to determine the effect of L-carnitine supplementation on the productive performance and physiology of juvenile pacu (Piaractus mesopotamicus). A total of 288 pacu, with an initial average weight of 9.62±0.74 g, were fed experimental diets supplemented with 400, 800, 1,200, 1,600, and 2,000 mg kg-1 L-carnitine and a control diet (without supplementation), for 128 days. The following were evaluated: growth performance; carcass centesimal composition; intestinal, muscle, and hepatic histomorphologies; and oxidative stress. The fish hepatosomatic and viscerosomatic fat indexes increased with the inclusion of L-carnitine in the diets. The evaluation of carcass centesimal composition showed that the diets supplemented with 2,000 mg kg-1 L-carnitine caused a reduction in protein content and an increase in that of ethereal extract. Intestinal histomorphology indicated changes in the villi with L-carnitine supplementation. Moreover, hepatic lipid peroxidation occurred with the inclusion of 2,000 mg kg-1 L-carnitine. The supplementation with L-carnitine in the diets of pacu juveniles does not influence the development of the fish until the rate of 1,600 mg kg-1. However, high carcass lipid levels, as well as an increase in the hepatosomatic and viscerosomatic fat indexes, are observed in fish fed diets containing 2,000 mg kg-1.摘要：本研究旨在探究左旋肉碱（L-carnitine）添加对幼短盖巨脂鲤（Piaractus mesopotamicus）生产性能与生理状态的影响。试验共选取288尾初始平均体重为9.62±0.74 g的该鱼种幼鱼，分别投喂添加了400、800、1200、1600、2000 mg·kg⁻¹左旋肉碱的实验日粮，以及1组无添加的对照日粮，试验周期为128天。本试验评估指标包括生长性能、鱼体百分组成、肠道、肌肉与肝脏组织形态学以及氧化应激水平。随着日粮中左旋肉碱添加量的提升，试验鱼的肝体脂肪指数与脏体脂肪指数均显著升高。对鱼体百分组成的分析结果显示，添加2000 mg·kg⁻¹左旋肉碱的日粮可显著降低鱼体粗蛋白含量，同时提升乙醚浸出物（粗脂肪）含量。肠道组织形态学观察表明，添加左旋肉碱会导致肠绒毛结构发生改变。此外，当日粮左旋肉碱添加量达到2000 mg·kg⁻¹时，试验鱼肝脏出现脂质过氧化现象。研究表明，在幼短盖巨脂鲤日粮中添加不超过1600 mg·kg⁻¹的左旋肉碱，不会对鱼体生长发育产生显著影响；但当日粮添加量达到2000 mg·kg⁻¹时，试验鱼会出现较高的体脂水平，同时肝体脂肪指数与脏体脂肪指数也会升高。