Response Of Digestive Enzymes Research Articles

Mechanisms of Digestive Enzyme Response to Acute Salinity Stress in Juvenile Yellowfin Tuna (Thunnus albacares).

This study investigates the effect of a sudden change in salinity for 48 h on the digestive enzyme activity of juvenile yellowfin tuna. The treatment included a control salinity of 32‱ in natural seawater and an experimental salinity of 29‱. Acute stress experiments were carried out on 72 juvenile yellowfin tuna (646.52 ± 66.32 g) for 48 h to determine changes in digestive enzyme activity in different intestinal sections over time (0 h, 12 h, 24 h, 48 h). The activities of pepsin, trypsin, α-amylase, lipase, and chymotrypsin in the digestive organs (stomach, foregut, and pyloric ceca) of juvenile yellowfin tuna were measured. Pepsin and pancreatic protease in the experimental group were significantly lower than in the control group (p < 0.05). α-amylase showed a fluctuating trend of decreasing and then increasing, and its activity trend was pyloric ceca > foregut > stomach. The lipase activity of gastric tissues decreased at the beginning and then increased, reaching a minimum at 24 h (2.74 ± 1.99 U·g protein-1). The change of lipase in the pyloric ceca and foregut was increasing and then decreasing. The lipase activity trend was pyloric ceca > foregut > stomach. The chymotrypsin showed a decreasing and increasing trend and then stabilized at 48 h with a pattern of pyloric ceca > foregut > stomach. Similarly, the gut villi morphology was not significantly altered in the acutely salinity-stressed compared to the non-salinity-stressed. This study suggests that salinity may change the digestive function of juvenile yellowfin tuna, thereby affecting fish feeding, growth, and development. On the contrary, yellowfin tuna is highly adapted to 29‱ salinity. However, excessive stress may negatively affect digestive enzyme activity and reduce fish digestibility. This study may provide a scientific basis for a coastal aquaculture water environment for yellowfin tuna farming, which may guide the development and cultivation of aquaculture.

Differential modulation of digestive enzymes and energy reserves at different times after feeding in juveniles of the marine estuarine-dependent flatfish Paralichthys orbignyanus (Valenciennes, 1839).

Integrative studies are lacking on the responses of digestive enzymes and energy reserves in conjunction with morphological traits at distinct postprandial times in marine estuarine-dependent flatfishes of ecological and economic importance, such as Paralichthys orbignyanus. We determined total weight (TW), hepato-somatic index (IH), activities of digestive enzymes in the intestine, and the concentration of energy reserves in the liver and the muscle at 0, 24, 72, and 360 h after feeding in juveniles of P. orbignyanus. Amylase activity decreased at 72 h (about 30%). Maltase, sucrose, and lipase activities reached peak at 24 h (67%, 600%, and 35%, respectively). Trypsin and aminopeptidase-N activities at 24 and 72 h, respectively, were lower than those at t = 0 (53% and 30%). A peak increase in the concentration of glycogen and triglycerides in the liver (24 h) (86% and 89%, respectively) occurred. In muscle, glycogen and triglyceride concentrations were unchanged at 24 h and higher at 72 and 360 h (100% and 60%). No changes were found in TW, IH, free glucose in the liver and muscle, and protein in the liver. The protein concentration in the muscle sharply increased at 24 and 360 h after feeding (60%). The results indicate a distinct and specific response of central components of carbohydrate, lipid, and protein metabolism that could be adjustments at the biochemical level upon periods of irregular feeding and even of long-term food deprivation inside coastal lagoons or estuaries. The distinct responses of digestive enzymes in the intestine and energy reserves in the liver and muscle suggest the differential modulation of tissue-specific anabolic and catabolic pathways that would allow the maintenance of physical conditions.

Valorization of the insect waste as a source of dietary protein in replacing the fishmeal protein for the cage reared Pangasianodon hypophthalmus: An approach to search the alternate non-conventional feed resource of animal origin

A ninety days experiment was carried-out to evaluate the effect of dietary replacement of fishmeal (FM) (locally available dried non-defatted Coilia dussumieri V.) by graded inclusion levels of non-defatted non-mulberry Indian tropical tasar silkworm spent pupae (Antheraea mylitta D.) on growth performance, feed consumption, digestive enzyme response, body chemical composition, and intestinal cellular micro-morphological status of the reared striped catfish (Pangasianodon hypophthalmus S.). Five iso-nitrogenous (280 g protein kg-1) and iso-energic (19 MJ kg-1) extruded floating feeds were formulated by gradually replacing the FM with NDSWP (non-defatted silkworm pupae) at 0%, 25%, 50%, 75%, and 100% (on protein to protein basis) levels and the diets are designated as NDSWP0, NDSWP25, NDSWP50, NDSWP75, and NDSWP100, respectively. The contribution of calculated pupae crude protein was 0%, 4.75%, 9.50%, 14.25%, and 19% out of the total protein (28%) content in the respective diets. The experiment was executed in the floating net-cage located at the Maithon reservoir, India which is a field research station of ICAR-CIFRI, Barrackpore, Kolkata, India. The designated diets were randomly allocated to 10 numbers of experimental cages (each 5 ×5 ×3 m), in triplicates stocked with 2475 numbers (stocking density at 33 numbers per m3) of striped catfish in each replication and fed daily twice at 08.00 h and 16.00 h. The initial stocking size of the striped catfish fingerling was 16.56 ± 0.08 g. At the termination of the feeding experiment, the final body weight (g), individual weight gain (g), weight gained (%), feed conversion ratio (FCR), specific growth rate (SGR), and protein efficiency ratio (PER) found to be non-significantly different (p < 0.05) up to 50% protein replacement level (NDSWP50) in comparison to the control (NDSWP0). Among the biological indices, hepatosomatic index (HSI) exhibited a non-significant difference stretching to NDSWP50 treatment group with a distinct significant difference between NDSWP25 and NDSWP100 (p < 0.05), when, an inverse trend was recorded in relation to increasing pupae meal in the diets. Among the digestive enzymes, relatively higher protease enzyme activity was observed in the diet fed at NDSWP50 compared to the rest of the treatment groups, although, it was statistically non-significant (p > 0.05). Amylase and lipase enzyme activities recorded a significant difference among the treatment groups (p < 0.05). A higher amount of fish muscle crude protein was noticed in the NDSWP50 treated group than in the rest of the treatment groups. The lipid content of fish muscle indicated its higher content over the initial and exhibited an inverse relationship with moisture and ash content at the end of the experiment. Histo-morphology of gut tissue confirms the suitability of feeding pupae protein incorporated diet with the gradual replacement of fishmeal protein. The findings of the current feeding trial suggests that the inclusion of non-defatted non-mulberry silkworm pupae protein at 50% level of fishmeal protein substitution without compromising the growth performance, nutrient utilization, conversion of feed, and other biological indices, and economics of diet.

Effects on the Growth and Digestive Enzyme Activity in Nile Tilapia Fry (Oreochromis niloticus) by Lead Exposure

Lead is a metal capable of affecting physiology and metabolism in fish, including Nile tilapia (Oreochromis niloticus). However, few studies have evaluated the effects of lead on digestive enzyme activities in fry. At that stage, independent feeding begins, and there is increased demand and consumption of food, so chronic exposure to metal during this stage of development would cause null or minimal growth in organisms. In this study, fry from Nile tilapia was used to evaluate the effects of lead acetate by chronic exposure on the growth and the activities of the digestive enzymes after 30 and 60 days exposures. Four treatment groups 0.025, 0.050, 0.075 and 0.100 mg/L of lead acetate and a lead-free control were established. The activity of enzymes decreased, in the case of acidic proteases after 30 days and lipases after 60 days of exposure, from 0.025 and 0.050 mg/L of lead acetate, respectively. The amylase activity increased in metal-treated, while the chymotrypsin decreased partially at 60 days. Lipases decreasing activity might be causing an increase of triglycerides (lipids) and body mass observed during the first 30 days of exposure. Concentrations, equal to or above 0.075 mg Pb/L, cause significant effects on size and weight of fry, with nearly 54% lower than controls. At chronic exposure and early stage of development, the enzymatic activity is partially reduced along with body weight gain, which would affect subsequent growing and aquaculture production. The digestive enzyme response is discussed as a possible limited biomarker of exposure, to be used in biomonitoring.

Effect of feeding frequency on growth performance, blood metabolites, proximate composition and digestive enzymes of Lebranche mullet ( Mugil liza ) Juveniles

This study verified the effects of feeding frequency on growth, blood metabolites, digestive enzyme activities (alkaline protease, acid protease, amylase and lipase) and proximate composition of Lebranche mullet juveniles. Fish with initial weight of 13.6 ± 0.7 g were distributed in twelve tanks and fed one, three, five and seven times per day to apparent satiation for 60 days. While the final weight of fish fed only once a day attained just 15.4 ± 0.7 g, those fed five or seven times per day reached 54.0 ± 12.1 and 55.9 ± 6.1 g respectively. The feed consumption also increased at high frequencies, but feed efficiency was higher (76.7 ± 11.7%) when mullets were fed three times per day. In general, increasing feeding frequencies also increased blood content of metabolites (total protein, glucose, triglycerides and cholesterol), possibly due to increased intake and absorption of nutrients. The response of digestive enzymes correlated with feeding efficiency, with higher activity in fish fed three or five times per day. Concerning whole-body proximate composition, no significant difference was observed in protein, but lipid content increased significantly with feed frequency. Based on growth performance and biochemical responses, we recommend feeding Lebranche mullet juveniles three to five times per day.

Microplastics impair digestive performance but show little effects on antioxidant activity in mussels under low pH conditions

In the marine environment, microplastic contamination and acidification may occur simultaneously, this study evaluated the effects of ocean acidification and microplastics on oxidative stress responses and digestive enzymes in mussels. The thick shell mussels Mytilus coruscus were exposed to four concentrations of polystyrene microspheres (diameter 2 μm, 0, 10, 104 and 106 particles/L) under two pH levels (7.7 and 8.1) for 14 days followed by a 7-day recovery acclimation. Throughout the experiment, we found that microplastics and ocean acidification exerted little oxidative stress to the digestive gland. Only catalase (CAT) and glutathione (GSH) showed a significant increase along with increased microplastics during the experiment, but recovered to the control levels once these stressors were removed. No significant effects of pH and microplastics on glutathione peroxidase (GPx) and superoxide dismutase (SOD) were observed. The responses of digestive enzymes to both stressors were more pronounced than antioxidant enzymes. During the experiment, pepsin (PES), trypsin (TRS), alpha-amylase (AMS) and lipase (LPS) were significantly inhibited under microplastics exposure and this inhibition was aggravated by acidification conditions. Only PES and AMS tended to recover during the recovery period. Lysozyme (LZM) increased significantly under microplastic exposure conditions, but acidification did not exacerbate this effect. Therefore, combined stress of microplastics and ocean acidification slightly impacts oxidative responses but significantly inhibits digestive enzymes in mussels.

The responses of digestive enzymes in juvenile and adultRapana venosa(Valenciennes, 1846) to different temperatures

The veined rapa whelk, Rapana venosa (Valenciennes, 1846), is an important and valuable fishery species; however, it has not been routinely artificially cultured on a large scale. Here, we studied the effect of temperature (6, 16, 22 and 28°C) on the digestive enzymes in R. venosa of different sizes (Juvenile (small, S: 1.2–1.8 cm) and adult (medium, M: 4.1–5.2 cm; large, L: 7.6–8.9 cm)) by detected the enzyme activity in different digestive glands (the salivary gland, Leiblein's gland (oesophageal gland) and liver) using spectrophotometric method, to determine the optimal temperature for artificial cultivation and to explore the feeding habits of this whelk. The optimal temperature was determined to be approximately 22°C. The food intake was significantly higher at 22°C than at other temperatures, and the activity of the digestive enzyme, trypsin, was at the highest in the main digestive gland of R. venosa, the liver, at 22°C. In addition, the observed presence of cellulase and α-amylase may suggest that carbohydrates are necessary during R. venosa development. The results of this study will help in the formulation of technical procedures for R. venosa aquaculture and in preventing its overexploitation, and explained its invasion mechanism to some extent.

Proteolytic digestive enzyme response in Japanese flounder larvae Paralichthys olivaceus fed two types of rotifers Brachionus plicatilis species complex

Two common live feeds, the Brachionus plicatilis species complex SS-type and L-type were used to assess whether there were any differences in protein hydrolysis and digestive trypsin activity in first feeding Japanese flounder. There were no significant differences in hydrolysis activity at 2, 3 and 7 days after hatching (DAH). At 5 DAH, hydrolysis activity was significantly higher in larvae fed SS-type (p < 0.05) at 50 kDa in 1.5- and 3-h incubation whereas L-type treatment had not completely hydrolyzed the proteins after 3 h at the same molecular weight. Larvae fed SS-type had significantly higher (p < 0.05) trypsin activity at 3, 5, 6, 7 DAH. Contribution of live prey to trypsin fraction in larvae showed significantly higher (p < 0.05) fraction for SS-type at 5 DAH (2.18 ± 0.44%) and 6 DAH (2.04 ± 0.29%) and the effect of exogenous trypsin from live prey was relatively low when compared to the total trypsin activity in larvae. This study discusses the differences in ability to digest proteins in Japanese flounder when fed different rotifer morphotypes and highlights the adaptability of this species to alternative rotifer morphotypes during its early developmental stages.

Response of digestive enzymes and esterases of ecotoxicological concern in earthworms exposed to chlorpyrifos-treated soils.

Assessment of organophosphorus (OP) pesticide exposure in non-target organisms rarely involves non-neural molecular targets. Here we performed a 30-d microcosm experiment with Lumbricus terrestris to determine whether the activity of digestive enzymes (phosphatase, β-glucosidase, carboxylesterase and lipase) was sensitive to chlorpyrifos (5 mg kg-1 wet soil). Likewise, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in the wall muscle and gastrointestinal tissues as indicators of OP exposure. Chlorpyrifos inhibited the acid phosphatase (34% of controls), carboxylesterase (25.6%) and lipase activities (31%) in the gastrointestinal content. However, in the gastrointestinal tissue, only the carboxylesterase and lipase activities were significantly depressed (42-67% carboxylesterase inhibition in the foregut and crop/gizzard, and 15% lipase inhibition in the foregut). Chlorpyrifos inhibited the activity of both cholinesterases in the gastrointestinal tissues, whereas the AChE activity was affected in the wall muscle. These results suggested chlorpyrifos was widely distributed throughout the earthworm body after 30 d of incubation. Interestingly, we found muscle carboxylesterase activity strongly inhibited (92% of control) compared with that detected in the gastrointestinal tissues of the same OP-exposed individuals. This finding was explained by the occurrence of pesticide-resistant esterases in the gastrointestinal tissues, which were evidenced by zymography. Our results suggest that digestive processes of L. terrestris may be altered by chlorpyrifos, as a consequence of the inhibitory action of the insecticide on some digestive enzymes.

Host‐associated divergence in the activity of digestive enzymes in two populations of the gypsy moth Lymantria dispar (Lepidoptera: Erebidae)

AbstractThe gypsy moth is a generalist insect pest with an extremely wide host range. Adaptive responses of digestive enzymes are important for the successful utilization of plant hosts that differ in the contents and ratios of constituent nutrients and allelochemicals. In the present study, we examined the responses of α‐amylase, trypsin, and leucine aminopeptidase to two tree hosts (suitable oak, Quercus cerris, and unsuitable locust tree, Robinia pseudoacacia) in the fourth, fifth, and sixth instars of gypsy moth larvae originating from oak and locust tree forest populations (hereafter assigned as Quercus and Robinia populations, respectively). Gypsy moths from the Robinia forest had been adapting to this unsuitable host for more than 40 generations. To test for population‐level host plant specialization, we applied a two‐population × two‐host experimental design. We compared the levels, developmental patterns, and plasticities of the activities of enzymes. The locust tree diet increased enzyme activity in the fourth instar and reduced activity in advanced instars of the Quercus larvae in comparison to the oak diet. These larvae also exhibited opposite developmental trajectories on the two hosts, i.e. activity increased on the oak diet and decreased on the locust tree diet with the progress of instar. Larvae of the Robinia population were characterized by reduced plasticity of enzyme activity and its developmental trajectories. In addition, elevated trypsin activity in response to an unsuitable host was observed in all instar larvae of the Robinia population, which demonstrated that Robinia larvae had an improved digestive performance than did Quercus larvae.

Digestive flexibility in response to environmental salinity and temperature in the non-symbiotic sea anemone Bunodosoma zamponii

In spite of their ecological importance in tidal pools, studies on digestive flexibility in non-symbiotic anemones (i.e., without symbiosis throughout their life) upon changes in key environmental factors are lacking. This study constitutes the first work to investigate the response of digestive enzymes in relation to high environmental salinity and temperature in a non-symbiotic sea anemone. We determined the occurrence and biochemical characteristics of maltase activity and compared maltase and proteolytic activities in mesenterial filaments in Bunodosoma zamponii from the intertidal area of Punta Cantera, Mar del Plata, Argentina (38°05′S, 57°32′W) acclimated to 35 and 40 psu and after an acute enhancement (15 min) of temperature from 20° to 30°C. Maltase activity was higher in 40 psu and upon the increase in temperature (about 80 and 99%, respectively). Proteolytic activity was not affected in any case. The results suggest the occurrence of specific digestive adjustments in relation to high salinity and temperature. The fact that differential modulation of maltase activity could be associated with a higher digestive capacity for glycogenic substrates is discussed.

Testing the adaptive plasticity of gypsy moth digestive enzymes in response to tannic acid using phenotypic selection analysis

The adaptive significance of plasticity of digestive enzyme responses to allelochemical stress was tested on 32 full-sib gypsy moth families from an oak forest (the Quercus population) and 26 families from a locust-tree forest (the Robinia population), reared on control or tannic acid-supplemented diets. By using the relative growth rate as a fitness measure in phenotypic selection analyses, we revealed that higher specific activity of leucine aminopeptidase in Quercus larvae and lower specific activity of trypsin in Robinia larvae were adaptive in the control environment. In Quercus larvae, elevated specific activities of leucine aminopeptidase and lipase were adaptive in the stressful environment. There were no plasticity costs for the enzyme activities in either experimental group. The obtained results suggest that adaptive plasticity of digestive enzyme activity in gypsy moth larvae contributes to optimal growth rate under various environmental conditions.

Adaptive phenotypic plasticity of gypsy moth digestive enzymes

Abstract The adaptiveness of plasticity of digestive enzyme responses to allelochemical stress was tested on 32 full-sib families of gypsy moth larvae from an oak forest population (the Quercus population) and 26 families from a locust-tree forest (the Robinia population), reared either on control diet, or on tannin-supplemented diet. Using the duration of larval development as an indirect measure of fitness, phenotypic selection analyses revealed that lower specific activities of total proteases and trypsin, and higher specific activity of leucine aminopeptidase were adaptive for both populations in the control environment. Plasticity was only shown to be costly for total proteases and trypsin activity in Quercus larvae. In a stressful environment, the most apparent adaptive response was a significant increase in lipase activity. There was no plasticity cost for lipase activity. The two populations differed in the direction of selection acting on α-glucosidase activity, which favoured decreased activity in Quercus larvae and increased activity in Robinia larvae in the control environment. α-glucosidase activity in Quercus larvae is characterized by cost of homeostasis, while cost of plasticity was shown for Robinia larvae. The results obtained on the plasticity of digestive enzyme activity indicate how this generalist species copes with variation in plant allelochemicals.

Responses of digestive enzymes and body lipids to weaning times in yellowtail kingfishSeriola lalandi(Valenciennes, 1833) larvae

The optimal time to wean fish larvae from live feed to artificial feed was explored in yellowtail kingfish Seriola lalandi (YTK). The same weaning regime started at five different days post hatching (DPH), namely 10 DPH (W10), 13 DPH (W13), 16 DPH (W16), 19 DPH (W19) and 22 DPH (W22). The activities of trypsin, lipase and alkaline phosphatase were detected in fish from 8 DPH throughout the experiment, but pepsin activity was first detected in fish on 15 DPH in the W10 and W13 treatments. The increase in pepsin activity was concomitant with the decrease in trypsin activity. Total fish lipids after weaning reduced by 40% in the W10 and W13 treatments, and increased by 20% in the W19 and W22. Fish survival rate in the W22 treatment was significantly higher than that in the W10 and W13 treatments. The results suggest that 16 DPH is the earliest day to wean and the best weaning window for YTK larvae should be 19–22 DPH. This study provides enzymatic evidence to guide the weaning process for YTK larvae, and offers a useful approach to explore optimal weaning time for fish larvae.

One-year monitoring of core biomarker and digestive enzyme responses in transplanted zebra mussels (Dreissena polymorpha)

A 12-month active biomonitoring study was performed in 2008-2009 on the Vesle river basin (Champagne-Ardenne, France) using the freshwater mussel Dreissena polymorpha as a sentinel species; allochthonous mussels originating from a reference site (Commercy) were exposed at four sites (Bouy, Sept-Saulx, Fismes, Ardre) within the Vesle river basin. Selected core biomarkers (acetylcholinesterase (AChE) activity, glutathione-S transferase (GST) activity, metallothionein concentration), along with digestive enzyme activities (amylase, endocellulase) and energy reserve concentrations (glycogen, lipids), were monitored throughout the study in exposed mussels. At the Fismes and Ardre sites (downstream basin), metallic and organic contamination levels were low but still high enough to elicit AChE and GST activity induction in exposed mussels (chemical stress); besides, chemical pollutants had no apparent deleterious effects on mussel condition. At the Bouy and Sept-Saulx sites (upstream basin), mussels obviously suffered from adverse food conditions which seriously impaired individual physiological state and survival (nutritional stress); food scarcity had however no apparent effects on core biomarker responses. Digestive enzyme activities responded to both chemical and nutritional stresses, the increase in energy outputs (general adaptation syndrome-downstream sites) or the decrease in energy inputs (food scarcity-upstream sites) leading to mid- or long-term induction of digestive carbohydrase activities in exposed mussels (energy optimizing strategy). Complex regulation patterns of these activities require nevertheless the use of a multi-marker approach to allow data interpretation. Besides, their sensitivity to natural confounding environmental factors remains to be precised.

Induced and constitutive responses of digestive enzymes to plant toxins in an herbivorous mammal

Many plants produce plant secondary compounds (PSCs) that bind and inhibit the digestive enzymes of herbivores, thus limiting digestibility for the herbivore. Herbivorous insects employ several physiological responses to overcome the anti-nutritive effects of PSCs. However, studies in vertebrates have not shown such responses, perhaps stemming from the fact that previously studied vertebrates were not herbivorous. The responses of the digestive system to dietary PSCs in populations of Bryant's woodrat (Neotoma bryanti) that vary in their ecological and evolutionary experience with the PSCs in creosote bush (Larrea tridentata) were compared. Individuals from naïve and experienced populations were fed diets with and without added creosote resin. Animals fed diets with creosote resin had higher activities of pancreatic amylase, as well as luminal amylase and chymotrypsin, regardless of prior experience with creosote. The experienced population showed constitutively higher activities of intestinal maltase and sucrase. Additionally, the naïve population produced an aminopeptidase-N enzyme that was less inhibited by creosote resin when feeding on the creosote resin diet, whereas the experienced population constitutively expressed this form of aminopeptidase-N. Thus, the digestive system of an herbivorous vertebrate responds significantly to dietary PSCs, which may be important for allowing herbivorous vertebrates to feed on PSC-rich diets.

Digestive enzyme response to natural and formulated diets in cultured juvenile spiny lobster, Jasus edwardsii

A better understanding of the nutritional requirements and digestive processes are essential for improving the consumption and growth of spiny lobsters on formulated diets used in commercial culture. Differences in the enzymatic digestive response (i.e., post-prandial changes in digestive enzyme activity, digestive fluid pH and digestive gland structure) of juvenile Jasus edwardsii fed either a natural (mussel flesh) or a formulated diet were investigated. Digestive enzyme activities (total protease, trypsin, α-amylase and α-glucosidase) and soluble protein concentration in the foregut after a single feeding event for the two dietary treatments displayed a common peak at 4 h, and a second peak at 18 h post-prandial for the mussel fed lobsters only. In lobsters fed the formulated diet, the lumen size of the digestive gland tubules was 88% larger, the number of B-cells per tubule at 18 h post-feeding was 269% higher, and the pH of the digestive gland was lower (6.20 versus 6.34) than in lobsters fed mussel flesh. These results indicated an intensified intracellular digestion in the digestive gland on the formulated diet that could have played a role in the poor appetite revival (>18 h) exhibited on this diet. Rearing of juvenile lobsters on the formulated diet for 6 months resulted in a marked decrease in the digestive capacity (i.e., total and specific enzyme activity of the foregut and digestive gland) and nutritional condition of lobsters. Overall, these results suggest that difficulty in the digestive processing of formulated feeds may help to explain the bottlenecks encountered in developing more effective formulated diets for juvenile spiny lobster culture. Improvements in the dissolution of dietary ingredients upon entering the foregut, and in the digestibility of dietary carbohydrate sources, may assist in further improving the performance of formulated diets for lobsters.

Responses of digestive enzymes of tambaqui (Colossoma macropomum) to dietary cornstarch changes and metabolic inferences

Digestive enzyme responses plus metabolic implications were studied in tambaqui (Colossoma macropomum) fed isoproteic diets containing 28% crude protein, 3300 kcal of gross energy/kg and different amounts of cornstarch (30, 40 and 50%). Amylase, maltase, acid protease, trypsin and chymotrypsin from the alimentary tract were assayed. Plasma, liver and white muscle metabolites were gauged to profile metabolism of the fish. The alimentary tract of tambaqui is compartmentalized morphologically and enzymatically. Amylase was present through the gut; acid protease was detected in stomach; maltase, trypsin and chymotrypsin were found in pyloric caeca and proximal and distal intestine sections. Increase of cornstarch levels from 40 to 50% in the diet resulted in an increase in amylase and maltase. Trypsin and chymotrypsin were unresponsive to starch levels. Acid protease follows the protein/carbohydrate ratio decrease. The increase of dietary cornstarch resulted in liver glycogenesis and the increase in plasma triglycerides is suggestive of lipogenesis. Digestive biochemical responses of tambaqui correlated with changes of feeding plus the analyses of metabolic profile are assumed as a tool for optimizing diet formulation and are a clue to other feeding optimizations for freshwater tropical species.

Digestive enzyme responses of tambaqui (Colossoma macropomum) fed on different levels of protein and lipid

The adaptation of digestive proteases, amylase and lipase was studied in tambaqui fed with 350, 253, 301 and 205 g kg−1 of crude protein, and 49, 81, 113 and 145 g kg−1 of lipid, in isocaloric diets. Digestive protease increased when dietary protein increased in stomach, where the highest specific activity was observed. Unspecific protease activity in intestine was very low. Lipase was observed throughout the gastrointestinal tract, and higher activities were observed in the stomach. However, pyloric caecum and the anterior and posterior intestines were the responsive sections to the dietary lipid. Amylase was detected throughout the gastrointestinal tract, but pyloric caecum was the most relevant amylase producer. Positive correlations were observed between anterior intestine lipase versus dietary lipid and pyloric caecum amylase versus dietary protein. Tambaqui is responsive to the food composition adapting the main digestive enzymes to the best profile.

Digestive enzymes and metabolic profile of Labeo rohita fingerlings fed diets with different crude protein levels

Labeo rohita, commonly called rohu is one of the most important fish species for aquaculture in India. Digestive enzyme response and metabolic profile of fingerling L. rohita to different dietary crude protein (CP) levels (viz. 25, 30, 35 and 40%) were studied in an attempt to optimize a practical diet formulation for this species. After 45 days of feeding, activity of digestive enzymes and metabolite concentrations were assayed. Amylase, lipase and alkaline phosphatase (ALP) activities were not influenced by the dietary protein, but proteolytic and acid phosphatase (ACP) activities varied ( P < 0.05) between the treatments. Proteolytic activity showed a second order polynomial relationship with dietary crude protein (CP) as Y = 0.0734 X 2 + 4.937 X − 68.37, r 2 = 0.97. A positive correlation was observed between dietary CP and amylase ( r 2 = 0.78). All the metabolites except muscle glucose showed significant change corresponding to the dietary protein levels. Glucose and glycogen levels corresponded to the dietary carbohydrate levels. Muscle and plasma pyruvic acid increased as the crude protein in the diet increased, whereas liver pyruvic acid showed the opposite trend. Muscle protein content was not affected by dietary CP. Protein fractions in plasma (total protein, albumin and globulin) showed maximum values in 30% CP fed group. It is concluded that proteolytic activity and ACP are the major digestive enzymes responsive to dietary CP in L. rohita fingerlings. Considering the cost effectiveness of the diet, and based on liver and plasma free amino acid levels and plasma protein fractions, 30% crude protein is recommended as the optimal dietary protein for L. rohita fingerlings.