Effects of processing on Duckweed (Lemna minor) as fish feedstuff

The nutritional value of duckweed (Lemna minor) has been investigated as a suitable substitute for soybean meal in aquafeed. However, information on its processed forms in the diets for better nutrients utilization are yet to be reported. Therefore, this research investigated the effects of treated duckweed meal (DWM) as soybean substitute. The proximate composition, anti-nutritional factors and amino acids concentration of raw (Ra), cooked (Co) and soaked in potash (So) DWM were evaluated using standard methods. Crude protein of the test ingredients varied from 22.70% (Ra) to 29.45% (Co). Anti-nutrient factors of saponin, tannins and cyanide were significantly (p<0.05) reduced from 0.72±0.01% to 0.41±0.01%, 64.00±0.29 (mg/100g) to 20.50±0.29 (mg/100g) and 4.88±0.01 (mg/100g) to 2.61±0.35 (mg/100g) in Ra and Co samples, while oxalate and phytate significantly (p<0.05) reduced from 219.00±0.58 to 65.00±0.58 (mg/100g) and 732.84±0.37 to 165.80±0.52 (mg/100g) in Ra and So, respectively. However, the value of alkaloid (%) was significantly (p<0.05) increased from 4.10±0.58 (Ra) to 4.70±0.01 (So). There were also increase in the total amino acids, total essential amino acids and total non-essential amino acids of the treated (Co and So) DWM over the Ra, as well as the essential amino acid score of So over Co and Ra DWM samples. The implication of the processing revealed that nutritional and amino acid content was enhanced with substantial reduction in phytochemicals except alkaloids.