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

Abstract

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.

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

“…A reduction in T/C ratio in the HP-diet fish, relative to NP-diet fish, caused by a greater increase in the activity of chymotrypsin over trypsin confirmed a reduction in growth rate (Table 2). This has been reported in several works [11,12,14,18,32]. The confirmation is also strengthened by the observed associations between trypsin specific activity and high growth and between chymotrypsin specific activity and low growth (Table 4).…”

“…Therefore, the conventional study for dietary protein requirement through optimal weight gain in fish (recently, i.e., [1,3,5,6,8]) should probably instead indicate the effect of optimal dietary protein level on the change of fish growth performance to greater increase in length than weight. It is interesting to note that fish with different growth capacities [current work] and trypsin phenotypes [14,38] have different protease digestive abilities. Fish from high growth group had a relatively higher digestive ability for all feed types, compared to those from low and medium growth groups (Figure 7).…”

“…Within each dietary group, these relationships were not significant, except for the negative correlation in the HP-diet group between intestinal weight and trypsin specific activity Figure 2(a)) and between final weight and trypsin specific activity (R 2 = 0.09, P < .03). The observations of similarity in slope T/C ratio ( Figure 3) between the HP-diet (0.222) and the NP-diet (0.212) groups, and the lack of the relationship between trypsin specific activity and the T/C ratio (see details in [12,14]) indicated that the fish were at a similar steady growth phase at sampling at the end of the experiment. .001; Figure 4).…”

“…Traditionally in aquaculture, dietary protein and lipid are varied throughout the life cycle to optimise the economic return. In the current work, we aim to understand a basic knowledge on long-term protein growth by investigating the effects of maintaining dietary protein and lipid concentrations throughout the fish life cycle on digestive efficiency and protein growth using a unique combination of techniques recently described by Rungruangsak-Torrissen's research team [11,12,14]. In addition, we also aim to study the potential for maximising protein growth efficiency in rainbow trout (Oncorhynchus mykiss Walbaum) families with differences in growth capacity by varying the concentrations of dietary protein and lipid.…”

“…The digestive efficiency was studied at the end of the experiment at the late stage of life cycle. It is advantageous to use the different methods simultaneously, as they could precisely provide practical important biological informations between fish groups with differences in genetics (growth capacity) and environmental impacts (diet quality) that could not be explained by using growth parameter alone, especially when feeding regime were not completely under control see [11,12,14]. Intestinal, gonad, and carcass weights were measured.…”