Effect of dietary tea supplementation on growth performance, fat content, and muscle fatty acid profile of rainbow trout

Authors: Welker, Thomas; WAN, XIAO-CHUN - Anhui Agricultural University; ZHOU, YI-BIN - Anhui Agricultural University; YANG, YAN-OU - Anhui Agricultural University; Overturf, Kenneth - Ken; Barrows, Frederic; Liu, Keshun

Submitted to: Aquaculture International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2016
Publication Date: 6/1/2017
Citation: Welker, T.L., Wan, X., Zhou, Y., Yang, Y., Overturf, K.E., Barrows, F., Liu, K. 2017. Effect of dietary tea supplementation on growth performance, fat content, and muscle fatty acid profile of rainbow trout. Aquaculture International. 25(3):1073–1094.

Interpretive Summary: Green tea is gaining in global popularity due to a number of associated health benefits. Of these benefits, increased fat metabolism and weight loss have garnered the most attention in recent years, and green tea and its bioactive compounds have been marketed as a weight loss solution. Salmonid fish cultured commercially for human consumption often contain high levels of body fat, which are linked to reduced yield and added difficulties in trout processing. Lower body fat accumulation is a desirable commercial processing trait in salmonids, and research has shown that green tea can lower body fat content and alleviate obesity to some extent in terrestrial mammals. Use of green tea to reduce body fat in fish has not been studied, and green tea supplemented in rainbow trout diets may be beneficial in the reduction of body fat content. In this study, three varieties of green tea were supplemented into feed of rainbow trout at 0, 1, 2, and 4% of diet. Trout fed the highest level (4% of diet) of green tea had reduced body fat content and an improved muscle fatty acid (FA) profile (lower saturated and higher polyunsaturated FAs) compared to the other diets. However, these fish also grew slower. It is unclear why the body fat content and growth performance declined, but it may be related to reduced fat digestion in the gut or increased fat metabolism from green tea, which has been shown in terrestrial mammals.

Technical Abstract: Green tea is cultivated and consumed predominantly in Asia. Yet, recent reports of its health benefits have increased popularity outside of Asia, including in North America. Of these health benefits, improved fat metabolism and weight loss have garnered the most attention in recent years. Salmonid fish cultured commercially for human consumption often contain high levels of body and visceral fat due to a variety of reasons. High levels of visceral or intraperitoneal (IP) fat are linked to reduced yield and added difficulties in trout processing. In this study, three varieties of green tea were supplemented into feed of rainbow trout at 0, 1, 2, and 4% of diet. At the end of 60 days, fish were sampled to determine effects on growth performance, fat content (whole body and IP), and muscle fatty acid (FA) profile. Trout fed the highest level (4%) of green tea had reduced IP fat content and an improved muscle FA profile (lower saturated FA and higher polyunsaturated FA) compared to the other diets. However, these fish also had lower growth performance. These effects did not appear to be caused by reduced feed intake (% body weight/day), which actually increased as green tea in diet increased. It is unclear why the IP fat content and growth performance declined, but it may be related to lower fat digestibility in the gut or increased fat metabolism from dietary supplementation of green tea, which has been shown in terrestrial mammals.