Abstract
BackgroundThe protein source from fish meal is very important in trout feeding, but it is expensive and very scarce. Alternative nutrient sources are required to achieve sustainability as trout production rapidly grows in Peru. The objective of this research was to determine the proximate chemical composition and the apparent digestibility coefficient (ADC) of dry matter, organic matter, crude protein, crude fat, and digestible energy of hydrolyzed sheep (HSS) and alpaca (HSA) skins in juvenile rainbow trout.MethodsA total of 450 fishes were randomly distributed in nine digestibility tanks, with 60.0 ± 1.32 g of initial weight and 6.4 kg/m3 of stocking density. The water quality parameters were as follows: pH 8.4, temperature 11.5 °C, and dissolved oxygen 6.2 mg/l. The skin hydrolysates were treated at 130 °C with 15 psi pressure for 120 min. Fish were fed a reference diet and an experimental diet containing 70% reference diet and 30% skin hydrolysate. The ingredients of the diets were mixed and then extruded at 95 °C with 4-mm diameter (Extruder Khal® EE800). The ADC was determined by the indirect method using insoluble ash as a non-digestible marker.ResultsThe ADC in HSS and HSA was similar for dry matter (67.7 vs 69.1%), organic matter (66.9 vs 68.2%), crude protein (70.4 vs 70.1%), and digestible energy (3.35 vs 3.24 Mcal/kg DM), but crude fat values were different (12.3 vs 48.0%; p < 0.001, respectively).ConclusionThe hydrolyzed sheep and alpaca skins had a high content of macronutrients with an acceptable apparent digestibility of nutrients, making them a viable alternative to improve the nutritive value of more economical feeds for rainbow trout feed.
Highlights
The protein source from fish meal is very important in trout feeding, but it is expensive and very scarce
The chemical composition and gross energy (GE) between hydrolyzed skins of sheep (HSS) and HSA were significantly different before digestion (Table 2): organic matter (OM) (92.6 vs 95.2%, p < 0.001), crude protein (CP) (69.2 vs 76.7%, p < 0.01), crude fat (CF) (12.0 vs 7.0%, p < 0.001), ash (7.4 vs 4.8%, p < 0.001), and GE (5.79 vs 5.41 kcal/g, p < 0.001), respectively
The apparent digestibility of CF was statistically significant between HSS and HSA diets (12.3 vs 48.0%; p < 0.001)
Summary
The protein source from fish meal is very important in trout feeding, but it is expensive and very scarce. Alternative nutrient sources are required to achieve sustainability as trout production rapidly grows in Peru. The production of rainbow trout (Oncorhynchus mykiss) has been increased significantly lately, and in the Puno region alone, has reached ~ 43,290 t per year ([PRODUCE] Ministerio de la Producción 2017). Studies in rainbow trout have shown that it is possible to substitute raw materials, such as vegetables (Adelizi et al 1998; Zhang et al 2012; Daniel 2018; Ortiz-Chura et al 2018) or other animal protein sources (Pfeffer et al 1994; Steffens 1994; Pares-Sierra et al 2014; Javaherdoust et al 2019), in replace for fish meal without significantly affecting the nutrition composition and biological performance of the fish
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