One of the central organs of the gastrointestinal tract is the pancreas. It plays an active role in regulating the digestive system by secreting enzymes that hydrolyze proteins, lipids, and carbohydrates from food (Kuzmina et al. 2024Kuzmina, I.V., Tolpygo, S.M., Kotov, A.V., Shoibonov, B.B. & Zamolodchikova, T.S. 2024. Basal pancreatic secretion in a comparative aspect in poultry and rodents. Frontiers in Physiology, 15: 1340130, ISSN: 1664-042X. https://doi.org/10.3389/fphys.2024.1340130. ). Regarding poultry farming, researchers has been reported in the scientific literature that shows the adaptation of the digestive glands of animals to the chemical composition of foods (Vertiprakhov et al. 2023Vertiprakhov, V.G., Trukhachev, V.I. & Ovchinnikova, N.V. 2023. Trypsin cycling in poultry is associated with metabolic regulation. Frontiers in Physiology, 14: 1226546, ISSN: 1664-042X. https://doi.org/10.3389/fphys.2023.1226546. ).
In studies performed by Martínez-Pérez et al. (2021)Martínez-Pérez, M., Vives, Y. & Pérez-Acosta, O. 2021. Nutritional value of palm kernel meal, fruit of the royal palm tree (Roystonea regia), for feeding broilers. Cuban Journal of Agricultural Science, 55(3): 305-313, ISSN: 2079-3480. https://www.cjascience.com/index.php/CJAS/article/view/1026/1339., where royal palm nut meal was included in the broilers diet, it was shown that the protein fraction of this fruit is considered relatively low (8.77 %) and that the levels of ether extract are high (16.06 %). Vertiprakhov et al. (2020)Vertiprakhov, V.G., Grozina, A.A., Fisinin, V.I. 2020. The exocrine pancreatic function in chicken (Gallus gallus L.) fed diets supplemented with different vegetable oils. Agricultural Biology, 55(4): 726-737, ISSN: 2412-0324. https://doi.org/10.15389/agrobiology.2020.4.726eng. , when analyzing different sources of vegetable oils in laying hens, observed that the exocrine function of the pancreas is modified depending on the source under study. The objective of this study was to study the pancreatic trypsin enzymatic activity in broilers which intake royal palm nut meal.
A total of 40 HE21 hybrid male broilers with an average initial live weight of 141±5 g were used. They were housed in metal cages from 8 to 42 days of age. The experimental diets consisted of: control (corn-soybean cake) and the inclusion of 5, 10 and 15 % of royal palm nut meal, so that they remained isoproteic and isoenergetic. The formulation was made for the start, growth and finishes stages, reported by Vives et al. (2020)Vives, Y., Martínez-Pérez, M., Alberto, M. & Hernández, Y. 2020. Pancreatic lipase enzymatic activity in broilers fed with Roystonea regia fruit meal included in the ration. Technical note. Cuban Journal of Agricultural Science, 54(1): 101-105, ISSN: 2079-3480. https://www.cjascience.com/index.php/CJAS/article/view/940/1021. . Throughout the experiment, broilers had free access to water and food.
At 42 d, the broilers were weighed and slaughtered, exactly two hours and thirty minutes after food ingestion. Traditional procedures were used: desensitization by stunning with electric shock before the exsanguination method by jugular puncture. Subsequently, the abdominal cavity was opened and the pancreases were removed. They were weighed on a technical scale (SARTORIUS, Germany) and expressed relative to live weight (g.kg-1 of LW). Then, they were immersed in 4 mL.g-1 of physiological saline solution, between 0 and 4 ºC, for transfert to the laboratory. The organs of three animals per treatment, which constituted a sample, were manually homogenized and centrifuged at 1500 r.p.m for 10 min at 4 ºC in a Thermoscientific IEC CL31R (China) refrigerated centrifuge. The pellet was discarded and the supernatant was stored in small aliquots at -80 °C until further analysis.
Protein concentration was determined by the Bradford (1976)Bradford, M.M. 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Analytical Biochemistry, 72(1-2): 248-254, ISSN: 0003-2697. https://doi.org/10.1016/0003-2697(76)90527-3. method on a UV-vis spectrophotometer (Rigol Ultra-3400 series, China). Concentrations were calculated by interpolating absorbance values of samples in the standard curve of bovine serum albumin (BSA) (0.01-5 mg/mL). This was normalized for all homogenates under study at 3 mg/mL, for which the corresponding dilutions were made in each case. All analyses were performed in triplicate.
Trypsin activity was determined in pancreatic homogenate, according to the technique described by León et al. (2007)León, M., Rueda, E., Castañeda, M., Méndez, A. & Michelangeli, C. 2007. Efecto de la concanavalina A sobre la actividad de las enzimas α-amilasa y tripsina en pollos de engorde. Revista Científica FCV-LUZ, 17(1): 83-88, ISSN: 2521-9715. https://produccioncientificaluz.org/index.php/cientifica/article/view/15261/15236. . The same (0.3 mg of protein) was incubated for 15 min at 41 °C with 200 μL of the 1 % casein substrate in 100 mM pH 7.4 sodium phosphate buffer. The reaction was stopped with the addition of 1 mL of 5 % w/v trichloroacetic acid and the mixture was filtered through Whatman 42 paper. 250 μL of the filtrate was reacted with 1,250 μL of 200 mM Na2CO3 and 250 μL of the Folin-Ciocalteu reagent, diluted 1:5 in distilled water. After incubation for 20 min at 41 °C, the absorbance was measured at a wavelength of 625 nm. The values were compared with those of a standard curve prepared from a tyrosine solution (1 mg/mL). The specific activity of trypsin was expressed as mg of tyrosine released.min-1.mg-1 of protein.
A completely randomized design was used, with four treatments. For the final and relative live weights of the pancreas, a total of 10 replicates from one animal were used and for the pancreatic trypsin enzymatic activity, three replicates, which corresponded to a sample of three pancreases each. Differences between means were determined according to Duncan (1955)Duncan, D.B. 1955. Multiple range and multiple F tests. Biometrics, 11(1): 1-42, ISSN: 0006-341X. https://doi.org/10.2307/3001478. for p<0.05 where necessary. The statistical package Infostat (Di Rienzo et al. 2012Di Rienzo, J.A., Casanoves, F., Balzarini, M.G., González, L., Tablada, M. & Robledo, C.W. 2012. InfoStat. Versión 2012, [Windows], Universidad Nacional de Córdoba, Argentina: Grupo InfoStat. Available: http://www.infostat.com.ar.) was used.
There were not differences in the final live weights and relative weights of the pancreas among the four treatments (table 1). Similar performance was recorded by Vives et al. (2021)Vives, Y., Martínez-Pérez, M. & Hernández, Y. 2021. Morphometric indicators of broilers fed Roystonea regia fruit meal in the ration. Technical note. Cuban Journal of Agricultural Science, 55(2): 181-184, ISSN: 2079-3480. http://www.cjascience.com/index.php/CJAS/article/view/1019/1327. , when studying the accessory gland in broilers. These authors also suggested that, although macroscopically no morphometric changes were observed, there was an increase in its specific functions due to the presence of royal palm nut meal in the ration, which favors the digestion process.
| Weights | Inclusion of royal palm nut meal , % | SE± | p-value | |||
|---|---|---|---|---|---|---|
| Control | 5 | 10 | 15 | |||
| Final live (kg) | 2.24 | 2.36 | 2.34 | 2.15 | 0.15 | 0.7506 |
| Pancreas (g.kg-1 LW) | 2.93 | 2.58 | 2.50 | 2.45 | 0.21 | 0.3910 |
The treatments with the inclusion of 5 and 10 % of royal palm nut meal did not differ from each other, and showed higher enzymatic activity of pancreatic trypsin compared to the rest (figure 1). The increase represents a physiological benefit for the animal, since according to Vertiprakhov et al. (2023)Vertiprakhov, V.G., Trukhachev, V.I. & Ovchinnikova, N.V. 2023. Trypsin cycling in poultry is associated with metabolic regulation. Frontiers in Physiology, 14: 1226546, ISSN: 1664-042X. https://doi.org/10.3389/fphys.2023.1226546. this enzyme breaks protein bonds through hydrolysis to form smaller peptides or amino acids that are more easily digestible and bioavailable. In this way, the digestion of these biomolecules increases, which perform essential biological functions in the body: structural, enzymatic, hormonal, regulatory, homeostatic, among others.
The 15 % reduction in enzymatic activity compared to the other treatments that include royal palm nut meal can be related to the high correlation showed by Martínez-Pérez et al. (2021)Martínez-Pérez, M., Vives, Y. & Pérez-Acosta, O. 2021. Nutritional value of palm kernel meal, fruit of the royal palm tree (Roystonea regia), for feeding broilers. Cuban Journal of Agricultural Science, 55(3): 305-313, ISSN: 2079-3480. https://www.cjascience.com/index.php/CJAS/article/view/1026/1339. between the fat and fiber contents (86 %) provided by royal palm nut with this level in the diet. According to Liu et al. (2017)Liu, S.Y., Selle, P.H., Raubenheimer, D., Gous, R.M., Chrystal, P.V., Cadogan, D.J., Simpson, S.J. & Cowieson, A.J. 2017. Growth performance, nutrient utilisation and carcass composition respond to dietary protein concentrations in broiler chickens but responses are modified by dietary lipid levels. British Journal of Nutrition, 118(4): 250-262, ISSN: 1475-2662. https://doi.org/10.1017/S0007114517002070. lipids have a greater impact on food intake than starch and protein, and the concentrations of the latter are diluted by the inclusion of additional lipids in the ether extract of isoenergetic diets. Vertiprakhov et al. (2020)Vertiprakhov, V.G., Grozina, A.A., Fisinin, V.I. 2020. The exocrine pancreatic function in chicken (Gallus gallus L.) fed diets supplemented with different vegetable oils. Agricultural Biology, 55(4): 726-737, ISSN: 2412-0324. https://doi.org/10.15389/agrobiology.2020.4.726eng. stated that at high physiological concentrations of fat, a selective increase in lipase is observed with an overall decrease in the rest of the enzymatic secretion. This result is consistent with that expressed by Vives et al. (2020)Vives, Y., Martínez-Pérez, M., Alberto, M. & Hernández, Y. 2020. Pancreatic lipase enzymatic activity in broilers fed with Roystonea regia fruit meal included in the ration. Technical note. Cuban Journal of Agricultural Science, 54(1): 101-105, ISSN: 2079-3480. https://www.cjascience.com/index.php/CJAS/article/view/940/1021. , who observed higher enzymatic activity of pancreatic lipase for 15 % inclusion of royal palm nut meal in the ration of broilers.
Inhibitory effects on exocrine pancreatic secretion by nutrients, bile salts, some gastrointestinal hormones and trypsin inhibitors have been described (Kuzmina et al. 2024Kuzmina, I.V., Tolpygo, S.M., Kotov, A.V., Shoibonov, B.B. & Zamolodchikova, T.S. 2024. Basal pancreatic secretion in a comparative aspect in poultry and rodents. Frontiers in Physiology, 15: 1340130, ISSN: 1664-042X. https://doi.org/10.3389/fphys.2024.1340130. ). According to Singh and Kim (2021)Singh, A.K. & Kim, W.K. 2021. Effects of dietary fiber on nutrients utilization and gut health of poultry: A review of challenges and opportunities. Animals, 11(1): 1-18, ISSN: 2076-2615. https://doi.org/10.3390/ani11010181. , fiber increases the excretion of bile salts, which are responsible for the emulsification of lipids so that their digestion can occur. Therefore, this performance could also be associated with inhibitory effects by the fibrous fraction of royal palm nut. It could be that 15 % of royal palm nut meal in the diet increased the concentrations of trypsin inhibitors, which would reduce trypsin activity. This hypothesis needs to be confirmed with further studies.
It is concluded that the inclusion of up to 10 % of royal palm nut meal in the diet of broilers increases the activity of the pancreatic trypsin enzyme in the gastrointestinal tract.