«Abstract Animals do not respond uniformly to stress load. It leads to energy losses and body damage during stressor exposure. One of the hormones ...»
Stress load of calves In the course of the experiments, two calves were tested in the habituation test daily in the morning between 8:00 and 9:00 am. Chosen animals were selected from the group in the morning. They were taken to a neighbouring stall, where have available only water and hay. Differentiation of excitatory types of calves was done after 20 minute habituation test. Division of animals according to their nervous system excitability by excitatory types EHb+, EHb°, EHb- was done by a method of differentiation of excitatory types by a routine test of habituation according to (Debrecéni, 1990). We obtained the data for the differentiation according to the number of squares walked by individual animals in a habituation chamber during a 20 minute habituation test. The habituation test was conducted in a habituation chamber. Subsequently, for each animal, the appropriate type of excitation was determined. Habituation chamber has standard parameters 16 °C till 20 °C, 75% – 80% humidity, it is soundproof, normally lighting, the floor is divided into equal squares visually highlighted the size of which roughly corresponds to the length of the tested animal body. The movement of the animal in the chamber was monitored by web cameras. After habituation animals were taken blood from jugular vein by veterinary syringe. After habituation test and blood collected from the jugular vein again the animal was transferred to a shed.
Processing of blood samples Blood was collected from calves' jugular vein with a syringe (single self-priming plastic sampling tube). Blood sampling was allowed to clot in a refrigerator at 4 °C and after 4 to 6 hours, it was centrifuged at 1200 rpm for 10 min. Then serum was drawn in from the syringe and frozen in aliquots volume in eppendorf vessel until further processing at - 20 °C. In this way the blood was processed after individual blood collections during the experiments. Processing of samples by Petrák and Debreceni: Differentiation Of Stress Load Resistant Calves By The Help Of Insuli...
immunoenzymatic quantitative analysis ELISA - test. For the processing of IGF-I was used kit: Octeia Insulin like growth factor-1, IGF-I AC-27F1 ELISA (IDS Ltd. Boldon, England). Treatment of samples was transferred according to the work instructions for this kit. The optical absorbance was measured by (Microplate Reader Model DV 990BV4, UniEquip Deutschland).
Statistical processing Processing of the results was transferred by means of a spreadsheet application Excel, and statistical significance was evaluated using a t-test.
Results Stress load impacts the level of circulating IGF-I. With all calves, psychical form of the load caused the decline in circulation (Figure1). Between concentrations IGF-I in serum before and after psychical load significant difference was not found.
The average IGF-I concentration between individual blood collections depending on the type of excitation of the group of animals after 20 minutes of habituation is shown in Figure 1.
Figure 1. Changes in concentrations of IGF-I in circulation with calves after psychical load in the group of calves (n = 21).
The average IGF-I concentration between individual blood collections depending on the type of excitation of the group of animals after 20 minutes of habituation is shown in Figure 2.
Figure 2. Changes in concentrations of IGF-I in circulation with the calves differentiated according to types of excitation (EHb+ n=9), (EHb° n=7), (EHb- n=5) during individual psychical loads in the group of calves (n = 21).
The highest average resting level of IGF-I concentration reached animals belonging into EHb+. On the other side, the lowest average resting levels of IGF-I reached animals belonging into Ehb-. The highest average level of IGF-I in the blood after habituation was with the calves EHb+ and the lowest with the calves EHb°. Within of individual type of excitation in a concentration IGF-I before and after load significant difference was not found.
Discussion From a breeding point of view, there are used markers currently that indicate the individual properties of the individual. Differentiation of animals according to a habituation test can not be done globally. From this point of view, we are looking for a particular genetic or biochemical indicator. When we simply determine this indicator, we can determine which excitatory type of animal we are dealing with.
During the effect of stress, there occur mainly catabolic processes in the body. Effort of the organism is to reduce these changes. In this process, IGF-I plays an important role thanks to its anti-apoptotic, growth and proliferative effects (Brywe, 2005; Butt, 1999). IGF-I protects the cells of the CNS, but also other organ systems from an excessive damage during stress load. Lack of IGF-I may have an impact on learning processes (Dick, 2003). With its protective properties it appears to be a suitable target of a research. In our experiments we found out that the level of IGF-I in circulation after an intensive psychical load reduction, which probably shows its intensive use by organism during the effect of load. Animals with higher resting concentrations of IGF-I are in habituation tests classified into EHb+ type that withstand the stress the best. This probably refers to a genetically or physiologically fixed functional feature of increased basal levels of IGF-I that has the protective and anti-catabolic effect in the organism. Conversely EHb- animals have practically unchanged IGF-I concentrations before and after load. This phenomenon is probably Petrák and Debreceni: Differentiation Of Stress Load Resistant Calves By The Help Of Insuli...
related to the use of a permanent supply of IGF-I in the body in the aftermath of damage to cells and organ systems during load. This type of excitation is in permanent strain as confirmed by Debrecéni (1999) on the basis of other biochemical indicators.
Conclusions IGF-I may protect cells of the individual from their damage during the stress load.
Increased resting concentrations of IGF-I are typical for individuals belonging into the category of highly excitable EHb+, which are able to adapt to not extreme demanding situations at behavioural level and do not burden biochemical adaptation mechanisms excessively. Our results suggest that higher concentrations of IGF-I in circulating blood is potentially suitable indicator for selection of calves with a better ability to adapt to stress breeding situations.
Acknowledgements This work was supported by projects VEGA 1/2717/12, ECACB - ITMS 26220120015
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