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

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.

Automated summary

The study evaluated the performance and welfare of bullfrogs in two production systems, finding that frogs raised in flooded pens showed better weight gain, growth rate, protein efficiency, and feed conversion ratio than those raised in semi-flooded pens. Additionally, flooded pens had a higher percentage of medium-sized animals, while semi-flooded pens had a higher percentage of small animals. No differences were found in the performance variables between the types of pens and genders of the animals.