ABSTRACT A feeding trial was performed to assess dietary protein:lipid ratios for the grow-out phase of the bullfrog (Lithobates catesbeianus). Nine balanced isoenergetic diets were formulated, combining three different protein levels (300, 400, and 500 g kg−1) with three different lipid levels (50, 100, and 200 g kg−1), designated as P300/50L, P300/100L, P300/200L, P400/50L, P400/100L, P400/200L, P500/50L, P500/100L, and P500/200L. Additionally, a commercial fish feed, commonly used in Mexico to feed bullfrogs, was also tested during the experiment. Growth performance, animal performance parameters, carcass composition, and fatty acid profiles in muscle and liver were evaluated. The feeding trial results showed that all the experimental diets enhanced growth, feed conversion ratio, and frog-leg weight compared with the commercial diet. Bullfrogs had higher growth with 400 and 500 g kg−1 of dietary protein regardless of dietary lipid content. It was also notable that with the P500/200L diet, frogs doubled the weight of those fed the commercial diet. DHA, EPA, and total omega-3 fatty acids were double in muscle and two to eight times higher in the liver compared with the commercial diet. In all cases, the final proximal composition of carcass reflected the diet composition. It is suggested that a diet containing 400 g kg−1 of protein and 50 g kg−1 lipids (protein/lipid ratio: 7.4; gross energy: 18.2 MJ kg−1) is adequate for bullfrog performance during the grow-out phase to achieve market size in a shorter period, thus, reducing farming risks and production costs.

ABSTRACT Epitheliocystis is an emergent infectious disease affecting fish gills and skin worldwide. Few studies document their distribution in wild and cultured fish in Latin America. This study reports the epitheliocystis distribution and prevalence, histopathological index (HI), and its possible relation with other observed pathologies in the gills of cultured tilapias Oreochromis niloticus in ponds and cages of three states of southwestern Mexico. In Guerrero, the number of affected fishes was less (29.2%) compared to Oaxaca (39.8%) and Chiapas (49.1%), with significant difference (Gadj = 13.39, df = 2, P = 0.01). The size of the cysts was between 5.37 to 52.96 μm, and most of the analyzed fish showed a low number of cysts per gill arch. The prevalence by regions was varied (0 to 75%) and no correlation (r = -0.002, P = 0.659, n = 474) between epitheliocystis prevalence and type culture. The fish had a low infestation of Trichodina sp. and monogeneans plus different pathologies such as inflammation, eosinophilic cells, rodlet cells, telangiectasia, edema, and thrombosis. The correlation analyses show a low inverse correlation (r = -0.281, P = 0.000, n = 474) between epitheliocystis prevalence and fish weight; and a low correlation (r = 0.372, P = 0.000, n = 474) between epitheliocystis prevalence vs. HI. The presence of the pathologies registered in this study seems to be possibly associated with other conditions like water quality or toxicants. This research is the first scientific study documenting the presence and distribution of epitheliocystis in Mexico.