Saturated fat and cholesterol in Atlantic salmon (Salmo Salar L.) feeds are important for fish performance, fillet quality and colour

Summary

Reduced marine ingredients in feeds for farmed Atlantic salmon has resulted in reduced saturated fatty acids (SFA) and cholesterol (CHOL) in the feed. The consequences of this were investigated in a feeding trial with five different levels of SFA, ranging from 10 to 28 % of total fatty acids (TFA) in the feed. With a low fish meal and fish oil content, all these diets had a low basal level of CHOL (<500 mg/kg). Furthermore, the 10 % SFA and the 25 % SFA diets were also made with added CHOL (>2100 mg/kg), giving a factorial design with high/low SFA and high/low CHOL, in addition to the regression design with SFA. The results showed the biggest impact by low SFA levels, such as reduced growth coupled with increased feed intake and feed conversion ratio (FCR), possibly related to energy spent on endogenous production of SFA. A similar tendency on growth and FCR was also seen for CHOL, but less pronounced. Low SFA (10 % of TFA) also had a negative impact on fillet quality, resulting in increased liquid loss after freezing and thawing. Low SFA (10 % of TFA) and low CHOL (<500 mg/kg) in combination reduced muscle firmness, while both also had a negative impact on fillet colour and astaxanthin content. While neither SFA nor cholesterol are essential nutrients for salmon, as these can be produced endogenously, the current results show that levels should not be as low as 10 % SFA of TFA or < 500 mg/kg CHOL, which would compromise fish performance and fillet quality.