Specific Activities Of Chymotrypsin Research Articles

Ontogenetic development of digestive enzymes and in vitro digestibility of spotted Babylon (Babylonia areolata) veligers

The ontogenetic development of the main digestive enzymes and in vitro digestibility were investigated in spotted Babylon (Babylonia areolata) veligers. The collected specimens included fertilized eggs, trochophores, veligers, and settlement stage larvae. The activity of each studied enzyme showed strongly positive pairwise correlations with the activity of every other enzyme studied (r = 0.498–0.847, n = 60, p < 0.01). Pepsin showed the highest specific activity during the development of the veligers (p < 0.05). Pepsin and chymotrypsin specific activity followed broadly similar trends, except in late trochophore and early veliger stages. Trypsin specific activity was highest in early-stage veligers. Amylase specific activity progressively increased in middle-stage veligers, and decreased in older veligers. Cellulase activity started to increase before hatching, exhibiting its highest activity during the first seven days of veliger development. Lipase specific activity increased progressively in early-stage veligers and then decreased and remained constant until the end of observation. The in vitro digestibility assay showed that three mixed rations (75:25, 25:75, and 0:100 w/w) of Chaetoceros sp. and Isochrysis sp., and single components of Spirulina meal, and clam feed were suitable for early-stage veligers, while all mixed rations of Chaetoceros sp. and Tetraselmis sp., and single components of Spirulina meal and herbivorous fish feed were suitable for late-stage veligers. Our findings can be used as a feed management reference for spotted Babylon veligers.

Mixed feeding schedule switching between high and low protein diets for Asian seabass (Lates calcarifer)

Mixed feeding schedule (MFS) switching between high (HP) and low (LP) protein diets has been used to improve growth and feed utilization in various fish species. In the current study, the optimal MFS was investigated in Asian seabass (Lates calcarifer) over the duration of an 8-week feeding trial. The fish (18.7 ± 0.1 g initial weight) were fed alternating between one day of HP and one day of LP diet (1 H/1 L), two days of HP and one day of LP (2 H/1 L), three days of HP and one day of LP (3 H/1 L), two days of HP and two days of LP (2 H/2 L), or three days of HP and two days of LP (3 H/2 L), and these treatments were compared to continuous feeding with HP (positive control, 403 g/kg protein and 86.1 g/kg lipid of feed basis) or with LP only (negative control, 333 g/kg protein and 55.7 g/kg lipid of feed basis). Twenty-one experimental units comprising fifteen fish each were set under a completely randomized design. At the end of experiment, growth performance and feed utilization parameters were similar between fish fed HP, 2 H/1 L and 3 H/1 L, followed by 3 H/2 L treatment, and all the fish in the alternating feed groups ingested a higher amount of HP than LP (P < 0.05). Economic analysis suggests that the most profitable schedule was 2 H/1 L among the tested feeding regimens. Specific activities of chymotrypsin, amylase, cellulase, lipase; and the amylase to trypsin ratio, indicated significant improvement in nutrient utilization and protein-sparing effect in the alternating treatments. There were no negative effects on muscle quality or carcass composition by the preferred alternating treatments (2 H/1 L and 3 H/1 L). Findings from the current study can be used to decide a practical feeding schedule for the commercial production of Asian seabass.

Ontogenic Development of Digestive Enzymes in Mealworm Larvae (Tenebrio molitor) and Their Suitable Harvesting Time for Use as Fish Feed

Mealworm larvae (Tenebrio molitor) are edible insects consumed in feed and food. In the current study, the optimal harvesting time of mealworm larvae for use as aquafeed was investigated during the ages of 30–90 days after hatching (DAH). Development of digestive enzymes, proximate composition, and in vitro protein digestibility using digestive enzymes from African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus), were used as criteria. The specific activities of pepsin and trypsin significantly decreased with age (p < 0.05) from the first harvesting time until 50 and 45 DAH, respectively, while steadiness in these enzyme activities was observed onwards. Chymotrypsin specific activity appeared constant across all harvesting times. The specific activity of amylase significantly decreased in the later stages of development, while cellulase exhibited a different pattern suggesting it has a major role in dietary fiber utilization relative to starch. Regarding proximate compositions of the mealworm larvae, the moisture and ash contents decreased significantly with age, while the protein content exhibited the opposite trend with the highest contents from 60 to 90 DAH. Crude lipid was generally fairly constant, but its lowest value was observed in the earliest stage. In vitro protein digestibility was not significantly different across all harvesting times for both fish species, except for the significantly decreased digestibility value at 65 DAH relative to 30 and 35 DAH for Nile tilapia. However, based on the economic benefits of time for growth increment and proximate chemical composition, approximately 60 DAH is proposed as suitable for harvesting mealworm larvae to be used in fish feed.

Protein nutrition on sub-adult triploid rainbow trout (1): Dietary requirement and effect on anti-oxidative capacity, protein digestion and absorption

An 80-day feeding trial was conducted to assess the dietary protein requirement of sub-adult triploid rainbow trout (initial average weight: 233 g). Six isolipidic and isoenergetic diets were formulated to contain increasing levels of protein (31.6, 35.4, 40.7, 43.3, 45.8 and 52.4%). Each diet was fed to quadruplicate groups of fish (100 fish per group) in freshwater cages. Results showed that weight gain rate (WGR), protein gain, whole-body protein content, trypsin and chymotrypsin specific activities in intestine significantly (P < 0.05) increased with increasing dietary protein level and then plateaued (P > 0.05). Protein retention, protein efficiency ratio (PER), lipase in pyloric caeca and amylase specific activities significantly (P < 0.05) decreased with increasing dietary protein level. Fish fed the diet with 45.8% protein had higher feed efficiency (FE) and higher enteric peptide transporter 1 (Pep T1) gene expression level. Generally, fish fed diets with low dietary protein levels had lower feed intake (FI), higher hepatosomatic index (HSI), higher plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, higher hepatic glutamate dehydrogenase (GDH) activity, as well as higher malondialdehyde (MDA) contents in plasma, liver and intestine and lower total anti-oxidative capacity (T-AOC) contents in plasma and intestine (P < 0.05). Based on WGR, the optimum dietary protein requirement of sub-adult triploid rainbow trout was 45.8% dry matter with a diet containing 20% lipid and 22 kJ gross energy/g. This optimal dietary protein level improved the digestive and absorptive abilities of rainbow trout. Diets with lower protein levels (31.6–35.4%) led to increase lipid peroxidation level in whole fish body, while the diet with excess protein (52.4%) appeared to limit enteric Pep T1gene expression level.

A study of the digestive enzyme activities in scaleless carp (Gymnocypris przewalskii) on the Qinghai-Tibetan Plateau

Two experiments were conducted to study the digestive enzyme activities in scaleless carp (Gymnocypris przewalskii) on the Qinghai-Tibetan Plateau. In experiment 1, the distribution of digestive enzymes in various digestive organs of G. przewalskii (body weight: 118.24 ± 9.48 g) was studied. Results showed that digestive enzyme specific activities in intestine were significantly higher than those in hepatopancreas (P < 0.05). In intestine, the highest levels of trypsin and chymotrypsin specific activities were found in foregut and hindgut, the highest levels of lipase and amylase specific activities were observed in foregut (P < 0.05). In experiment 2, temporal changes of the digestive enzyme specific activities after feeding were investigated in G. przewalskii (body weight: 305.32 ± 28.78 g). Results showed that lipase and amylase specific activities in foregut approached maximum levels at 2 h after feeding and then decreased to the basic level at 6 h after feeding. The trypsin specific activities in foregut and hindgut reached the maximum levels at 2 h after feeding and then to the basic level at 8 h after feeding. In conclusion, as stomach-less fish, foregut of G. przewalskii contributed more to the nutrients digestion. The fish could digest nutrients (protein, fat and carbohydrate) efficiently. Thus, increasing in the amount of G. przewalskii resources could be achieved by improving nutritional state in artificial culture systems.

PH Characterization of Digestive Enzyme and In vitro Digestibility of Red Bee Shrimp Caridina cantonensis (Decapoda: Atyidae)

The characteristics of digestive enzyme from red bee shrimp (Caridina Cantonensis), a tiny ornamental shrimp, were investigated under various pH ranging from 2 to 12. The aim of this study was to find out the specific activities of protease, amylase, lipase, cellulose, trypsin and chymotrypsin and in vitro raw materials by shrimp enzyme digestibility. Fifteen and sixty-day old shrimp were obtained from private farms in Bangkok, Thailand. Protease, lipase, amylase, cellulase, trypsin and chymotrypsin specific activity were determined. The results showed that protease activity had its optimal activity at pH ranging from 8 to 10 and showed the highest activity at pH 10 in both age groups. The alkaline amylase activities were found to be significantly higher than acidic amylase in both age groups. Both acidic and alkaline amylase activity of the 15-day old shrimp was significantly lower than the larger shrimp. The Lipase activity in the 60-day old shrimp showed the highest activity at pH 12, pH 10 and 11, respectively. In the 15-day old shrimp, the lipase activity was stable over a broad pH ranging from 2-12. In the 60-day old shrimp, the cellulase activity showed the highest activity at assay condition pH 7 and decreased when pH levels increased. In the 15-day old shrimp, cellulase activity showed optimal pH at pH 8 and 11. The trypsin and chymotrypsin activity at neutral to weak alkaline condition was greater under acidic condition in both age groups. The activity of 15-day old shrimp was significantly lower than the older shrimp. Regarding in vitro digestibility, the study on protein digestion showed that fish meal was suitable to be a protein source for red bee shrimp. The carbohydrate digestibility showed that wheat flour and maltodextrin were more appropriate as a carbohydrate source for red bee shrimp than cassava, rice bran and Na-alginate. Therefore, it can be concluded that red bee shrimp had diet digestibility in neutral to mid alkaline condition. The animal protein materials are appropriate to be red bee shrimp feed ingredients with low fiber and carbohydrate source.

Effects of feeding frequency on growth performance and digestive enzyme activity of sex-reversed Nile tilapia, Oreochromis niloticus (Linnaeus, 1758)

The effects were investigated of different feeding frequencies—one meal at 0600 h, two meals (at either 0600 h and 1200 h or 0600 h and 1800 h) and three meals daily (at 0600 h, 1200 h and 1800 h)—on the growth performance, digestive enzyme activity, muscle quality and carcass composition of sex-reversed fingerlings of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), in a recirculating aquaculture system over a 3 mth period. The experiment involved four replicates following a completely randomized design with 30 fish per replication. The growth performance of the fish fed twice daily at 0600 h and 1800 h and three times daily were similar (p > 0.05) and were higher than for the other treatments. There were no significant differences among the feed conversion ratios of all treatment groups over the 3 mth period. The specific activities of digestive enzyme, amylase, lipase, total proteases, trypsin and the ratios of trypsin to chymotrypsin and amylase to trypsin were similar among feeding frequencies. There was a significant decrease in the chymotrypsin specific activity in fish fed less often compared to the three-meals-daily group. The muscle quality and carcass composition were not affected by feeding frequencies, except for the muscle RNA. These results suggested a superior growth capacity of tilapias fed twice daily (0600 h and 1800 h) which may be of practical use in feeding management for tilapia farming.

Adaptive regulation of digestive serine proteases in the larval midgut of Helicoverpa armigera in response to a plant protease inhibitor

Protease inhibitors (PIs) are direct defenses induced by plants in response to herbivory. PIs reduce herbivore digestive efficiency by inhibiting insects' digestive proteases; in turn insects can adapt to PIs by generally increasing protease levels and/or by inducing the expression of PI-insensitive proteases. Helicoverpa armigera, a highly polyphagous lepidopteran insect pest, is known for its ability to adapt to PIs. To advance our molecular and functional understanding of the regulation of digestive proteases, we performed a comprehensive gene expression experiment of H. armigera exposed to soybean Kunitz trypsin inhibitor (SKTI) using a custom-designed microarray. We observed poor larval growth on the SKTI diet until 24 h, however after 48 h larvae attained comparable weight to that of control diet. Although initially the expression of several trypsins and chymotrypsins increased, eventually the expression of some trypsins decreased, while the number of chymotrypsins and their expression increased in response to SKTI. Some of the diverged serine proteases were also differentially expressed. The expression of serine proteases observed using microarrays were further validated by qRT-PCR at different time points (12, 24, 48, 72 and 96 h) after the start of SKTI ingestion. There were also large changes in transcriptional patterns over time in the control diet. Carbohydrate metabolism and immune defense genes were affected in response to SKTI ingestion. Enzyme assays revealed reduced trypsin-specific activity and increased chymotrypsin-specific activity in response to SKTI. The differential regulation of trypsins and chymotrypsins at the transcript and protein levels accompanying a rebound in growth rate indicates that induction of SKTI-insensitive proteases is an effective strategy of H. armigera in coping with this protease inhibitor in its diet.

Stage-Specific Ontogeny of Digestive Enzymes in the Cultured Common Dentex (Dentex dentex) Larvae

Stage-specific ontogeny of main digestive enzymes in common dentex, Dentex dentex, were assayed during early life development according to notochord flexion studied from hatching to 45 days after hatching (DAH). The notochord was straight in yolk-sac larvae of D. dentex and preflexion stage was observed between 0 and 18 DAH as 2.75 and 6.27 mm at total length (TL). Then, flexion of the notochord was estimated between 19 and 30 DAH as 6.27 and 10.9 mm at TL. Important alterations in specific activities of all digestive enzymes measured during period of this study were mostly related with metamorphosis and co-feeding. Trypsin and chymotrypsin specific activities were firstly detected on day 3 and were related with mouth opening, whereas they slightly increased until 25 DAH respectively. Pepsin was firstly detected on day 28 and related with stomach formation and a sharp increase was observed until 30 DAH. Both amylase and lipase were measured on day 2 and 4, respectively and they also sharply increased during the first week of life. Additionally, except pepsin, most of the digestive enzyme activities were firstly secreted in the preflexion stage and also gastric secretion started and functional development digestive system were occurred in in flexion and postflexion stages, respectively.

Development of Enzymes andIn VitroDigestibility during Metamorphosis and Molting of Blue Swimming Crab (Portunus pelagicus)

The work focuses on development of digestive enzymes (amylase, total protease, trypsin, and chymotrypsin) and activity ratio of trypsin to chymotrypsin (T/C ratio) for digestive efficiency and growth, in blue swimming crab (Portunus pelagicus) during metamorphosis and molting. Specific activities of all enzyme parameters studied were associated with growth during metamorphosis, while only those of trypsin and T/C ratio were associated during molting cycle where trypsin and chymotrypsin specific activities associated with consumption rate with especially high levels during late intermolt and early premolt stages. About 50% increased weight gain was observed with at least double increased T/C ratio at the end of molting period, compared to the stages prior to molting. Growth of carapace would be more significant after finishing molting. Carapace width gain and T/C ratio were highest at the first crab stage. Studies ofin vitroprotein digestibility of different feed raw materials indicated thatArtemia, Rotifer, andMoinaare the best for larval stages. Otherwise, the use of shrimp feed andArtemiaflake could be the alternatives. Incorporating of cassava meal into the feed formula for early adult stage (juvenile) could be an advantage. The proteins from animals are more beneficial for adult crab culture than the proteins from plants and bacteria. The digestible quality of dietary protein is very important during larval stages, while the protein level of diet is more important during adult stages with fully developed digestive enzymes.

Adaptive differences in digestive enzyme activity in the crab Neohelice granulata in relation to sex and habitat

Neohelice granulata (Dana, 1851) is a semi-terrestrial burrowing crab that inhabits estuaries and saltmarshes feeding on grasses or sediment depending on the microhabitat they occupy (vegetated saltmarsh or bare mudflat). Specific cellulolytic, amylolytic, and proteolytic enzyme activities were analyzed in midgut gland homogenates of males and females from each microhabitat fed in the laboratory with Spartina densiflora leaves and sediment, respectively, in order to detect sex, food and microhabitat related differences. The presence of β-1,4-glucosidase, endo-β-1,4-glucanase, α amylase, trypsin and chymotrypsin were confirmed. Specific cellulolytic activity was higher in crabs fed on leaves than in those fed on sediment or in no fed controls and variable differences between sexes were observed. Specific amylase activity of crabs fed on leaves was the lowest recorded. Trypsin and chymotrypsin specific activities were higher in saltmarsh crabs fed on leaves than in mudflat crabs fed on sediment. Different mechanisms of enzyme regulation to explain the observed differences among groups were suggested. Additionally, differences between sexes suggest different metabolic needs related to gonad maturation. It is concluded that N. granulata has the ability to adapt digestive enzyme production to support its physiological and metabolic needs based on the different food sources available at each microhabitat.

Effect of starvation and refeeding on digestive enzyme activities in juvenile roach, Rutilus rutilus caspicus

We evaluated the effects of starvation and refeeding on digestive enzyme activities in juvenile roach, Rutilus rutilus caspicus. Fish were divided into four feeding groups (mean mass 1.68 ± 0.12 g). The control group was fed to satiation twice a day throughout the experiment with formulated diet (SFK). The other three groups were deprived of feed for 1(S1), 2(S2), and 3(S3) weeks, respectively, and then fed to satiation during the refeeding period. The results showed that trypsin specific activity was not affected significantly either by starvation or refeeding, in all experimental groups. Chymotrypsin specific activity did not change significantly in S1 fish during the experimental period. In S2 and S3 fish no significant changes were observed during the starvation period. Upon refeeding, the activity increased in S2 fish, while it decreased in S3 fish. Amylase specific activity decreased significantly during the starvation period in all experimental groups. Upon refeeding, the activity increased. Alkaline phosphatase specific activity did not change significantly during the experiment period in S3 fish, while it showed significant changes during the starvation and refeeding period in the S1 and S2 fish. Starvation also had a significant effect on the structure of the intestine.

Ontogeny of the digestive tract and enzymatic activity in white seabass, Atractoscion nobilis, larvae

The development of the digestive system and digestive enzyme activity in white seabass larvae, Atractoscion nobilis, were analyzed from hatching until 40 days post hatch (dph) using histological and biochemical approaches. The development of the digestive system in A. nobilis larvae was similar to that reported for other marine fish species. Larvae at 3 dph (0.55 ± 0.001 mg wet weight and 3.6 ± 0.02 mm total length), cultured at 18 °C in seawater, presented all the structures (i.e. differentiation of the alimentary canal into the buccopharynx, esophagus, anterior and posterior intestines, pancreas with zymogen granules, liver, gall bladder and open mouth) necessary for the digestion and absorption of nutrients such as proteins and lipids (primarily). At this time, the larvae had fully-developed digestive systems that allowed them to digest inert feed and to absorb nutrients throughout the intestine walls. On the other hand, most digestive enzyme activities were detected at the moment of hatching. Trypsin activity was 0.80 ± 0.16 mU/mg protein at 1 dph (0.51 ± 0.001 mg wet weight larvae), and increased gradually during the following days, but most notably after the initial exogenous feeding at 4 dph. The specific activity of chymotrypsin was 7.21 ± 1.29 mU × 10 − 4 /mg protein at 1 dph and reached peak level (15.9 ± 1.02 mU × 10 − 4 /mg protein) at 18 dph (6.6 ± 0.003 mg wet weight larvae). The specific activity of leucine aminopeptidase increased continuously from 1.31 ± 0.05 mU × 10 − 3 /mg protein at 1 dph to 15.91 ± 0.40 mU × 10 − 3 /mg protein at 18 dph. The activity of α-amylase at 1 dph was 1.35 ± 0.09 U/mg protein, increasing to 8.07 ± 0.98 U/mg protein at 16 dph. The activity of pepsin was detected at a very low level (0.71 ± 0.53 U/mg protein) at 10 dph, and a stepwise increase in activity was observed between 16 and 20 dph, reaching maximum level (13.92 ± 0.09 U/mg protein) at 40 dph. These results indicate that the digestive tract develops rapidly in this species and that the stomach becomes functional between 16 and 18 dph. It should, therefore, be possible to start weaning the fish at this young age.

Different Dietary Levels of Protein to Lipid Ratio Affected Digestive Efficiency, Skeletal Growth, and Muscle Protein in Rainbow Trout Families

Normal Protein (NP) and High Protein (HP) diets were provided to rainbow trout families from juvenile to maturity. Muscle protein concentration increased during growth and the protein to lipid (P/L) ratio was doubled at late stage with respect to the dietary P/L ratio. The HP-diet fish showed higher protein deposition in body and white muscle, and had lower condition factor due to protein deposition associated more with body length than body weight. Fish growth rates were decreased at maturation, and the HP-diet fish showed lower growth rate including the activity ratio of trypsin to chymotrypsin (T/C ratio) and feed efficiency. Trypsin and chymotrypsin specific activities were related to dietary protein levels, and the T/C ratio was related to intestinal weight and growth rate independent of the enzymes specific activity levels. The families with high growth capacity could double increase white muscle P/L ratio levels, compared to low and medium growth families, if they were fed on HP-diet. The digestive enzyme extracts from high growth families resulted in higher in vitro protein digestibility for all diets. The effect of dietary P/L ratio on digestion, skeletal growth (length) and the white muscle P/L ratio in fish with different growth capacities is illustrated.

Digestive efficiency, free amino acid pools and quality of growth performance in Atlantic salmon (Salmo salar L.) affected by light regimes and vaccine types

This study comprised the results of three different seawater trials using unique combination of techniques to study protease digestive efficiency and growth performance quality to illustrate the effects of light regimes and vaccine types in Atlantic salmon (Salmo salar L.). Fish with higher growth had higher trypsin (T) and chymotrypsin (C) specific activities with higher T/C ratio or slope T/C ratio [calculated from the regression between trypsin (y) and chymotrypsin (x) specific activities] in the pyloric caeca. The T/C ratios indicated fish growth rates over a period of 1-2 months, while the slope T/C ratios indicated fish growth rates at sampling. Adaptation period for adjustment to the new environment of continuous light was 70 days, indicated by the differences in trypsin specific activities and the crossing of slope T/C ratio regressions following with the changes in growth rate directions between the control and the treated group. Vaccine types affected fish vertebral growth, and additional continuous light enhanced the impact of vaccines on fish growth during springtime, indicated by differences in slope T/C ratios. Continuous light stimulated fish growth during winter to spring, when the natural day length was short, without significantly changing white muscle and oocyte qualities in the fish of about 500 g, except for significantly increased white muscle RNA concentration. Continuous light also reduced fish growth rate later during summer, when the natural day length was long, by precedently decreasing the T/C ratio in late spring. Interestingly, plasma levels of free lysine related to tryptic digestion were correlated with trypsin specific activity levels. Continuous light caused higher levels of most free amino acids (FAA) involved in nitrogen metabolism, higher incorporation of essential FAA for protein synthesis, and higher protein turnover rate (free hydroxyproline levels) in both plasma and white muscle. However, continuous light did not affect higher protein content, intracellular buffering capacity and RNA levels in the white muscle of the fish of about 1 kg, probably due to limitation of FAA available for protein synthesis. It is therefore suggested that enhancing fish growth by continuous light stimulation should be accompanied by increasing availability or content of dietary protein (and probably minerals), which in turn would improve the quality of fish growth performance through increasing fillet protein concentration, strengthening vertebral growth, and delaying oocyte development.

Digestive enzyme activity of the red porgy (Pagrus pagrus, L.) during larval development under culture conditions

The ontogenic development of the main digestive enzymes (proteases, amylase and lipase) in the red porgy, Pagrus pagrus, larvae was assayed during the larval development. The green water technique was carried out for larval rearing and whole-body homogenates were used for enzymatic assays in triplicate. Significant alterations in specific activities of all digestive enzymes measured during the period of this study were mostly related to metamorphosis and weaning. Trypsin- and chymotrypsin-specific activities were first detected on day 3, together with opening of the mouth, and slightly increased until 25 days after hatching (DAH). After this period, the specific activities of these enzymes slightly decreased. Pepsin was first detected on day 28, concurrent with stomach formation, and a sharp increase was observed until 30 DAH. A slight decrease was measured from this date until the end of the experiment. Both amylase and lipase were measured for the first time on days 2 and 4 respectively, and the specific activities of these enzymes showed similar patterns during the first week of the study. Then, slight variations were observed until 30 DAH and while lipase-specific activity declined, an increase in the specific activity of amylase was found until the end of the experiment. It is concluded that the variations observed in the specific activity of digestive enzymes were related to either metamorphosis, such as the formation of the stomach (28 DAH), or to changes in food composition. The profile of the developmental pattern of the main digestive enzymes detected in P. pagrus is similar to that described for other Sparid species.

Ileal digestibility of protein and amino acids from canola meal in weaned piglets and growing pigs

Two experiments were conducted to measure the apparent ileal digestibility coefficients (AID) of protein and amino acids from canola meal (CM) and a pelleted canola meal (PCM) and their effect on specific activity (SA) of pancreatic proteases in weaned piglets and growing pigs. In experiment one, 24 piglets weaned at 17 days and weighing 5.5 kg were used. Treatments were a reference diet with 200 g of crude protein (CP) kg − 1 elaborated with casein (C) as the sole protein source, a diet containing C–CM and a diet containing C–PCM. These diets were obtained using the reference diet plus 100 g kg − 1 of CM or PCM that substituted an isoproteic mixture of casein and maize starch from reference diet, so that the AID coefficients for their protein and amino acids could be calculated by difference. In experiment two, nine castrated pigs weighing 39.5 kg were used. Treatments were a reference diet with 160 g of CP kg − 1 elaborated with casein (C) as the sole protein source, diet C–CM and diet C–PCM. These diets were obtained using the reference diet plus 300 g kg − 1 of CM or PCM that substituted an isoproteic mixture of casein and maize starch from reference diet. In piglets, the AID coefficients for casein were highest ( P < 0.05), those of PCM were intermediate, and those of CM were the lowest. In older pigs, the AID coefficients for casein were highest, and those of CM and PCM were similar ( P > 0.05). The SAs of chymotrypsin, trypsin and carboxypeptidases A and B were lower in piglets than in heavier pigs. Moreover, the SAs of trypsin, chymotrypsin, and carboxypeptidase B were lower ( P > 0.05) in animals fed casein. The results showed in piglets that whereas CM was less digestible, pelleted canola meal improved protein and amino acid ileal digestibility, resulting in similar AID coefficients to those of growing pigs.

DIGESTIVE EFFICIENCY, GROWTH AND QUALITIES OF MUSCLE AND OOCYTE IN ATLANTIC SALMON (SALMO SALAR L.) FED ON DIETS WITH KRILL MEAL AS AN ALTERNATIVE PROTEIN SOURCE

ABSTRACT Atlantic krill meal and Antarctic krill meal were tested to replace fish meal in Atlantic salmon diets. Different techniques were applied to precisely evaluate dietary quality and quality of fish growth performance. Inverse relationship between trypsin specific activity (T) and ratio of trypsin to chymotrypsin (T/C ratio) as a result of increased chymotrypsin specific activity (C) in the pyloric ceca indicated fish growth status as a reduction in growth rate. These protease values in the feces could also indicate fish digestive efficiency, but could not predict fish growth status. There were relationships among feed conversion efficiency (FCE), in vitro digestibility, and pyloric cecal T/C ratio, with inverse levels of krill meal in the diets. Krill meal seemed to increase muscle protein concentration through increasing protein retention, as capacity for protein synthesis was reduced. Dietary quality tests by in vitro digestibility were corresponded with growth studies, and indicated a possibility of inclusion of krill meal at 50–60% replacements, and larger fish were more sensitive to dietary quality than smaller ones. At 80–100% replacements, in vitro digestibility and FCE reduced, and oocyte quality changed through increased trypsin-like specific activity probably because of less or abnormal oocyte development. PRACTICAL APPLICATIONS The work illustrates differences in digestive efficiency and the quality of growth performance (protein growth efficiency and capacity for protein synthesis in muscle and oocytes) in fish feeding on diets with different levels of krill meal as fish meal replacer. The advantage of using various methods simultaneously for evaluating digestive efficiency and the quality of fish growth performance is to precisely provide reasonable information for some important biological differences between fish groups that could not be explained by using growth parameter alone, especially when the numbers of samples are not high. The methods are very practical for studying food quality, food utilization and growth quality of fish in different environmental conditions and with different behaviors in aquaculture as well as in natural ecosystem where food consumption rate cannot be measured. The in vitro digestibility method, using fish crude enzyme extracts and standardized by trypsin activity, could also compare the digestive ability between different species and provide information on food quality in fish growth trials that may not be necessary to be performed.

Effects of illumination on early life development and digestive enzyme activities in common pandora Pagellus erythrinus L. larvae

The activities of main digestive enzyme (proteases, amylase and lipase) and animal husbandry (mainly growth and survival) were studied in common pandora Pagellus erythrinus larvae until 30 days after hatching (DAH). Three different illumination levels (10, 30 and 100 lx) were compared in triplicate and green water technique was carried out. At the end of the experiment, illumination did not affect neither survival nor growth except 10 lx treatment. Similarly, specific growth rate (SGR) was different in 10 lx treatment ( p < 0.05), although no differences were found in group 30 and 100 lx treatments ( p > 0.05). In all groups, trypsin and chymotrypsin specific activities were firstly detected on day 3 related with mouth opening and slightly increased until 20 and 25 DAH respectively, and after this date specific activities of those decreased. Although, there was a significant difference between 10 lx treatment and other experimental groups ( p < 0.05), no differences were found in other treatments ( p > 0.05). Pepsin was firstly detected on day 25 related with stomach formation and sharp increase was observed until 30 DAH and then slight decrease was measured from this date and no differences were found between all groups. Amylase was firstly determined on day 2 and increased to day 5. After this date, slight decreases were measured in all groups and continued until end of experiments. The highest specific activity of amylase was determined in 30 lx treatment and no significant differences were found between groups ( p > 0.05). Lipase was firstly detected on day 4 and increased to day 10. Then, activity of lipase decreased until day 15 and increased again until 25 DAH. Slight decreases were found in all groups until day 30 and continued to end of experiments. No significant differences were detected among groups ( p > 0.05). Finally, the significant improvement in survival, larval development and specific enzyme activities of larvae were determined in 30 lx treated group. It is thought that this phenomenon is related to optimal keeping conditions provided by the medium illumination level for Pagellus erythrinus larvae.

Different expressions of trypsin and chymotrypsin in relation to growth in Atlantic salmon (Salmo salar L.)

The expressions of trypsin and chymotrypsin in the pyloric caeca of Atlantic salmon (Salmo salar L.) were studied in three experiments. Two internal (trypsin phenotypes, life stages) and three common external factors (starvation, feeding, temperatures) influencing growth rates were varied. Growth was stimulated by increased temperature and higher feeding rate, and it was depressed during starvation. The interaction between trypsin phenotype and start-feeding temperature affected specific activity of trypsin, but not of chymotrypsin. Trypsin specific activity and the activity ratio of trypsin to chymotrypsin (T/C ratio) increased when growth was promoted. Chymotrypsin specific activity, on the other hand, increased when there was a reduction in growth rate whereas fish with higher growth had higher chymotrypsin specific activity resulting in lower T/C ratio value. During a rapid growth phase, trypsin specific activity did not correlate with chymotrypsin specific activity. On the other hand, a relationship between specific activities of trypsin and chymotrypsin could be observed when growth declined, such as during food deprivation. Trypsin is the sensitive key protease under conditions favouring growth and genetically and environmentally affected, while chymotrypsin plays a major role when growth is limited or depressed. Trypsin specific activity and the T/C ratio value are shown to be important factors in the digestion process affecting growth rate, and could be applicable as indicators for growth studies of fish in captive cultures and in the wild, especially when food consumption rate cannot be measured.