Spike-topped apple snail (Pomacea diffusa) meal in guppy (Poecilia reticulata) diets: Effects on physical pellet quality, growth performance, colour intensity, stress tolerance, and economic efficiency

This study evaluated the effects of dietary inclusion of Spike-topped apple snail (Pomacea diffusa) meal on feed pellet quality, growth performance, colour intensity, stress tolerance, and economic efficiency in guppy (Poecilia reticulata). Four isonitrogenous and isoenergetic diets were formulated: a fishmeal-based control diet (CD) and three diets replacing fishmeal with snail meal (SM) at 25% (25 SM), 50% (50 SM), and 75% (75 SM). Snail meal inclusion increased feed pellet expansion (CD: -1.02%±5.15, 25 SM: 7.0%±5.34, 50 SM: 2.06%±6.53, 75 SM: 2.36%±6.89). A total of 360, 28-day-old male golden chest guppy fry (mean initial weight: 0.09 g) were randomly assigned to 12 outdoor tanks (n = 3) and fed with one of the experimental diets for 35 days under natural photoperiod. Growth performance and colour intensity of fish were assessed. At the end of the experiment, fish were exposed to 30 ppt salinity in a 500 mL pre-aerated water bath for stress response testing. Mean feed intake, specific growth rate, and feed conversion ratio were not significantly affected across diets. Guppies fed 25 SM and 50 SM showed significantly lower (p < 0.05) mean grey values, indicating enhanced caudal fin colour, as lower grey values correspond to more intense coloration. The 75 SM diet yielded the highest profit index and the lowest incidence cost. Survival during the stress test was similar across all treatments. These findings suggest that fishmeal can be replaced with snail meal up to 75% without negative impacts on feed pellet quality, and growth and stress tolerance of guppy, while 25%-50% replacement also enhances colour intensity, offering additional benefits.