Nutritional strategies can help fish manage stress, and functional feedstuffs are an interesting nutritional option. Therefore, this study evaluated the potential functional effect of spray-dried plasma (SDP) on Nile tilapia growth performance and the capacity of SDP to improve fish health under cold-induced stress (CIS). A total of 440 fish (12.64 ± 0.64 g) were randomly distributed into 40,250-L aquaria and fed five diets containing graded levels of SDP (0, 16.6, 33.2, 49.7 and 66.3 g kg − 1) for 60 days. The growth performance, villus height:crypt depth ratio, and hematological parameters were analyzed, and the same hematological parameters were then analyzed after 7 days of CIS. Based on the broken-line analysis of the FBW, SGR, RWG and FCR, the optimum dietary level supplementation of SDP was determined to be 49.70, 50.16, 51.83 and 41.83 g kg − 1 diet, respectively. The crypt depth and villus:crypt ratio were positively affected by SDP supplementation. After CIS, hematocrit of fish fed 16.6 g kg − 1 of dietary SDP was significantly lower than fish fed 66.3 g kg − 1 level (P < 0.05). The supplementation level of dietary SDP and the CIS affected the leukocyte, lymphocyte and neutrophil counts. The monocyte count was affected by the dietary SDP supplementation level both before and after CIS (P < 0.05). Total plasma protein concentration in the fish fed 49.7 and 66.3 g kg − 1 SDP were significantly higher than fed 16.6 g kg − 1 SDP after CIS (P < 0.05), and CIS led to a higher Albumin:Globulin ratio (P < 0.05). Dietary SDP supplementation improved the growth performance, intestinal health, hematological profile and CIS resistance of the studied fish. Based on our results, we recommend a dietary supplementation level of 51.83 g kg − 1 SDP for Nile tilapia.

The use of enzymes in animal feed is common practice nowadays and its utilization has shown good results for improving the efficiency of nutrient utilization. In this sense, the goal of this work was to add low cost fungal phytases and proteases, with promising biological characteristics, produced by Solid State Fermentation using agro-industrial co-products to improve nutritional availability of plant based diets for Nile tilapia. Considering the enzymes chosen for the digestibility trail, Aspergillus niger produced acid phytases, as A. oryzae, produced proteases withoptimum pH over 8. The enzymes were stable at high temperatures (90°C for phytase and 50°C for protease) and showed very distinct behavior when different substrates were tested. Subsequently, the upscale production of A. niger phytase and A. oryzae protease with 7000 U g − 1 and 2500 U g − 1 , respectively, were applied as additive in a plant protein based fish diet. They increased protein, mineral, energy and lipids availability (P ˂ 0.05), showing that these new enzymes can improve animal production and performance. Additionally, these low cost enzymes are an alternative as additives to improve soybean meal digestibility in fish plant based diets.

The aim of this study was determine the apparent digestibility coefficient (ADC) of dry matter (ADCdm), gross energy (ADCge), crude protein (ADCcp), amino acids (ADCaa), and phosphorus (ADCp) of the corn, rice bran and wheat bran subjected to extrusion process for Nile tilapia (Oreochromis niloticus) juveniles (101.6 ± 3.1 g). A reference diet (RD) was formulated based on soybean meal as protein source. Then, test diets were obtained by replacing 30% of the RD with the ingredients tested. Chromic oxide was used as inert marker (0.1%). Feces collection was performed by sedimentation tanks with conical bottom (300 L). The ADCcp and ADCaa were 66.71 and 69.9%, 59.71 and 66.08%, and 67.89 and 76.63% for corn, rice bran and wheat bran, respectively. Corn was considered the best energetic feed to Nile tilapia, for presenting the highest values of ADCdm (98.42%), ADCge (93.49%) and ADCp (67.16%).

The objective of this work was to evaluate the diet components -crude fiber, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, and lignin -as internal indicators in the determination of the apparent digestibility coefficients of dry matter, gross energy, and of the nutrients -crude protein, phosphorus, and amino acids -in Nile tilapia (Oreochromis niloticus). Groups of ten juveniles (80.3±1 g) were randomly distributed in six tanks of 250 L and fed two practical diets, either of a plant-origin diet or of a plant-and animal-origin diet. Both diets were supplemented with 0.1% chromium (III) oxide (Cr 2 O 3 ). Faeces were collected by the modified Guelph system. The apparent digestibility coefficients were determined by the content difference of the internal indicators, present in the diets and faeces, and compared by Dunnett's test to those obtained by the use of Cr 2 O 3 . Cellulose was effective in the determination of the apparent digestibility of dry matter, energy, and nutrients of both experimental diets; and the acid detergent fiber was effective only for the diet composed exclusively of plant-origin ingredients. The use of crude fiber, neutral detergent fiber, hemicellulose, and lignin as digestibility indicators was inefficient for the analyzed nutrients of both diets. Therefore, cellulose is the most suitable indicator for digestibility evaluation in Nile tilapia. Componentes da dieta como indicadores internos na determinação dos coeficientes de digestibilidade aparente em tilápia-do-niloResumo -O objetivo deste trabalho foi avaliar os componentes da dieta -fibra bruta, fibra em detergente neutro, fibra em detergente ácido, hemicelulose, celulose e lignina -como indicadores internos na determinação dos coeficientes de digestibilidade aparente da matéria seca, da energia bruta e dos nutrientes -proteína bruta, fósforo e aminoácidos -em tilápia-do-nilo (Oreochromis niloticus). Grupos de dez juvenis (80,3±1 g) foram aleatoriamente distribuídos em seis tanques de 250 L e alimentados com duas dietas práticas, ou com ingredientes de origem vegetal ou de origem vegetal e animal. Ambas as dietas foram suplementadas com 0,1% de óxido de cromo-III (Cr 2 O 3 ). As fezes foram coletadas pelo sistema Guelph modificado. Os coeficientes de digestibilidade aparente foram determinados pela diferença de teor dos indicadores internos, presentes nas dietas e nas fezes, e comparados, pelo teste de Dunnett, aos obtidos pelo uso de Cr 2 O 3 . A celulose foi efetiva na determinação dos coeficientes de digestibilidade aparente da matéria seca, da energia e dos nutrientes de ambas as dietas; e a fibra em detergente ácido foi efetiva apenas para a dieta que continha exclusivamente ingredientes de origem vegetal. A utilização de fibra bruta, fibra em detergente neutro, hemicelulose e lignina, como indicadores de digestibilidade, mostrou-se ineficiente quanto aos nutrientes analisados de ambas as dietas. Assim, a celulose é o indicador mais apropriado para a avaliação de digestibilidade em tilápia-do-nilo.Termo...