Rearing and fattening of bullfrogs (Lithobates catesbeianus) in semi-flooded and flooded systems: productive performance and plasmatic biochemical and blood count responses

Abstract

The present study aimed to evaluate productive performance and welfare of bullfrog (Lithobates catesbeianus) in two production systems, semi-flooded and flooded, during the rearing and fattening phases. Experiment I lasted 30 days and 600 bullfrog froglets (5.48 ± 0.57 g) were used, randomly distributed in six pens of 1.22 m2, three pens in a flooded system and three pens in a semi-flooded system (100 froglets/pen). Experiment II lasted 120 days and 204 bullfrogs (37.85 ± 1.55 g) were used, randomly distributed in six pens of 1.22 m2, three in a flooded system and three in a semi-flooded system (34 frogs/pen). In experiment I, productive performance and animals proportion per size range were statistically equal (P > 0.05) between the two systems. In experiment II, frogs reared in a flooded system had greater weight gain, specific growth rate, protein efficiency ratio, and better feed conversion ratio (P < 0.05). The animals raised in flooded pens had a higher (P < 0.05) percentage of medium animals (150–250 g), while the semi-flooded system had a higher (P < 0.05) percentage of small animals (<150 g). There was no difference (P > 0.05) between the types of pens on the large animals percentage (>250 g). There was no interaction (P > 0.05) between the types of pens and animals' sex on any of the performance variables evaluated. Regardless of sex, animals raised in flooded pens had a higher (P < 0.05) liposomatic index. On the other hand, only females reared in flooded pens had a higher (P < 0.05) gonadosomatic index. Regardless of the system, females had higher (P < 0.05) viscerosomatic index, males had higher (P < 0.05) carcass and legs yield. There was no influence (P > 0.05) of types of pens on erythrogram and white blood cells count of the frogs. Frogs reared in flooded pens showed higher levels of triglycerides and total cholesterol (P < 0.05). Differently, the types of pens did not influence (P > 0.05) the levels of glucose, lactate, plasmatic proteins, albumin, globulins, and the albumin/globulins ratio of bullfrogs. The types of pens did not influence the froglets growth during the rearing phase. Although, it is recommended that bullfrogs be fattened in a flooded pen, as the animals raised in this type of system presented better productive performance and did not altered their homeostasis.