The effect of temperature on feed consumption and nutrient absorption in Procambarus clarkii and Procambarus zonangulus

Feeding characteristics of acclimated red swamp crayfish Procambarus clarkii and white river crayfish Procambarus zonangulus were determined at 8, 14, 20, 26, and 32 C. Food consumption rates of crayfish were directly related to temperature. Feeding was minimal at 8 C. At 14 C P zonangulus consumed significantly more feed (5.5% body weight (BW/d) than P clarkii (1.8% BW/d). At 32 C R clarkii consumed significantly more feed (23% BW/d) than P zonangulus (10% BW/d), reflecting species-specific thermal optimums for feeding. Differences in food consumption rates correspond to differences in the geographical distributions of these two species. Dry matter absorption rates ranged from 55% to 75% for both species without significant temperature effect. Patterns of protein and carbohydrate absorption were similar in R clarkii and R zonangulus. Protein absorption efficiency decreased from 45% to 10% as temperature increased from 8 C to 32 C. The total amount of protein absorbed increased seven- to ten-fold as temperature increased. Soluble carbohydrate absorption efficiency was reduced at low temperatures. However, absorption efficiency increased approximately five-fold as temperature increased from 14 C to 20 C, but did not change substantially as temperature was increased to 32 C. The total amount of carbohydrate absorbed increased approximately 15- to 26-fold as temperature increased. The protein to carbohydrate utilization ratio was similar between species, but varied dramatically with temperature. Both species absorbed between 2.5 and four-times more protein than carbohydrate at low temperatures (8 C and 14 C). At 32 C both species utilized approximately three times more carbohydrate than protein. In spite of reduced consumption at lower temperatures, crayfish absorbed a greater protein portion. At these low temperatures it appears that crayfish maximize the efficiency of protein absorption, presumably for maintenance and growth requirements. At high temperatures it appears that crayfish maximize energy intake, presumably to sustain higher metabolic rates due to increased activity levels. These apparent temperature-dependent nutrient requirements may influence natural foraging strategies or, for species in aquaculture, the effectiveness of commercial feed preparations. At high temperatures R clarkii was more effective in consuming nutrients than P zonangulus and may be more successful than R zonangulus at these temperatures.