Animal performance and welfare of giant freshwater prawn (Macrobrachium rosenbergii) subjected to feed restriction

Behavior activities of giant freshwater prawn Macrobrachium rosenbergii juvenile, their performance, and acquired lesions when under temporary feed restrictions were analyzed. Five animals/experimental units (10 prawns/m2 ) were employed for treatments DFL ­ daily feed supply in the light phase; DFD ­ daily feed supply in the dark phase; AFL ­ alternating feed supply in the light phase; and AFD ­ alternating feed supply in the dark phase, for a 24-hour period, with four replications each. Prawns were fed a pellet diet, twice a day, with 10% of their biomass/day. Specimens were monitored during 60 consecutive days, with behavior recording daily and weighed every 10 days, with assessment of lesions and/or amputated limbs at the end of the experimental period. Types of behavior comprised exploring, grooming, inactivity, crawling, swimming, excavation, burrowing, agonism, and feed ingestion by scan sampling, with instantaneous registration every 60 s, in 15-min windows, before and after feed, in light and dark phases. Feed restricted in alternate days during light and dark phases did not interfere in growth or survival of the specimens, with increase in apparent feed intake and less feed conversion ratio and specific growth rate. Agonistic behavior was higher in specimens with feed restrictions, with an increase in the number of lesions and amputations. The above demonstrates welfare decrease in farmed M. rosenbergii and depreciation in the quality of the final product.(AU)

Behavior activities of Macrobrachium rosenbergii (De Man, 1879) in monosex and mixed populations, in the laboratory

Monosex all-male populations for the commercial breeding of the freshwater prawn Macrobrachium rosenbergii have been used to lessen the specimens´ aggressiveness and size heterogeneousness. The species´s behavioral variation in mixed, monosex all-male and monosex all-female populations, during the 24-h light-dark period, is assessed. The focal method, with instantaneous report, was employed, featuring a 15-m window for each aquarium, distributed in 12 time shifts throughout the light-dark phase. Eight aquariums contained four prawns each (10 prawns/m2), totaling 96 prawns, monitored for 160 h, during 30 days. Exploring, burrowing, covering with earth, feeding, cleaning, inactivity, crawling, swimming, change and agonistic activity were analyzed. The animals showed a high rate of autogrooming and exploitation during the light and dark phases in three culture modalities, whereas burrowing occurred more frequently during the light period. Agonism was more frequent during the dark phase in all populations, although rates of monosex all-female culture were higher during the light and dark phases when compared to mixed and monosex all-male cultures. The authors recommend shelters and substrates for protection and improvement of the animals´ welfare, especially during the dark shift. Since agonism was more frequent for monosex all-female culture when compared to that in mixed or monosex all-male culture, such population composition is not recommended.

Behavior activities of Macrobrachium rosenbergii (De Man, 1879) in monosex and mixed populations, in the laboratory

Monosex all-male populations for the commercial breeding of the freshwater prawn Macrobrachium rosenbergii have been used to lessen the specimens´ aggressiveness and size heterogeneousness. The species´s behavioral variation in mixed, monosex all-male and monosex all-female populations, during the 24-h light-dark period, is assessed. The focal method, with instantaneous report, was employed, featuring a 15-m window for each aquarium, distributed in 12 time shifts throughout the light-dark phase. Eight aquariums contained four prawns each (10 prawns/m2), totaling 96 prawns, monitored for 160 h, during 30 days. Exploring, burrowing, covering with earth, feeding, cleaning, inactivity, crawling, swimming, change and agonistic activity were analyzed. The animals showed a high rate of autogrooming and exploitation during the light and dark phases in three culture modalities, whereas burrowing occurred more frequently during the light period. Agonism was more frequent during the dark phase in all populations, although rates of monosex all-female culture were higher during the light and dark phases when compared to mixed and monosex all-male cultures. The authors recommend shelters and substrates for protection and improvement of the animals´ welfare, especially during the dark shift. Since agonism was more frequent for monosex all-female culture when compared to that in mixed or monosex all-male culture, such population composition is not recommended.(AU)