Work

Impacts of alfalfa nutrient concentrate on pellet physical attributes, growth performance, metabolism and nutritional quality of rainbow trout, Oncorhynchus mykiss

Year: 2024

Type: article

Abstract: This study addresses the escalating demand for aquatic feed by exploring the potential of alfalfa nutrient concentrate (ANC) as feed ingredient for rainbow trout. Test diets contained varying ANC levels (0%, 5%, 10%, 15%, and 20%) to replace fishmeal (32% in the 0% ANC diet) to achieve equal digestible protein and were processed using a cooking extrusion method. Analysis of feed pellets showed that pellet density increased with ANC levels, leading to sinking pellets at 20% ANC, accompanied by improved water stability, durability, and reduced oil leakage. Two feeding trials were conducted to test the diets in flow-through water systems with three replicates per diet. The first 8-week trial evaluated their impact on feeding, fecal physical quality, and the apparent digestibility coefficient (ADC) of dietary nutrients in rainbow trout (initial body weight, 18.2 ± 0.2 g). ANC inclusion did not impact the palatability and satiation feed intake of the fish (p > 0.050). However, the ADC of dry matter and phosphorus decreased in fish fed the 20% ANC diet (p <0.010). The second 9-week trial investigated the growth performance, nutrition quality, and metabolism of rainbow trout (initial body weight, 19.3 ± 0.2 g). While all fish exhibited substantial growth, fish fed diets with 10% to 20% ANC displayed lower growth rates and higher feed conversion ratios compared to those fed with 0% or 5% ANC (P<0.001). The whole body protein content was higher in fish fed 5% ANC compared to all other treatments (p = 0.030). The biochemical parameters of plasma were similar across treatments except for decreased plasma phosphorus levels in the ANC-based diets (p <0.033). Significant changes were observer in liver metabolism including tricarboxylic acid cycle, amino acid and energy metabolism pathways in fish fed the 20% ANC diet versus the 0% ANC diet (p < 0.050). These results demonstrate that ANC inclusion improved pellet physical quality without impairing feeding behavior and nutritional quality of the fish but inclusion ≥ 10% in the diet reduced fish growth. This study offers the first comprehensive assessment of the potential of ANC used in fish feed involving feed management, feeding evaluation, and the biological response.

Source: Animal nutrition

DOI: 10.1016/j.aninu.2024.07.011