The population of the Earth is increasing year by year and people need more and more food, which they have to produce on a territory of given extent, therefore only the increase of intensity can bring results. The increase of intensity means, among others, that we must improve the protection of our produce from pests therefore we must apply pesticide in agriculture in the future too, and we must create new compounds, must prove their efficiency, must find their possible ill effects on living creatures and the environment.
In agricultural production chemical plant protection is one of the most polluting areas. During the production and use of pesticide a huge amount of chemicals escape into our environment, whose biological activity, the toxic features of the agents are not known, despite the fact that the authorization process has changed a lot in the past decades.
Mainly the wildlife of the territories under agricultural cultivation and people working with pesticide impose themselves to the load of chemicals. Agricultural areas mean the habitat, hatching place and the source of food for our wild birds. The sprayed chemicals can have an effect on not only the mature birds but on the developing embryos in the eggs as well. The breeding period of pheasants is at the same time as the period of chemical plant protection work, therefore it is reasonable to deal with the harmful effects of pesticide on living creatures from an eco-toxicological point of view.
During the eco-toxicological testing of pesticide each chemical agent is applied separately but we cannot ignore the fact that the chemical load appears in a complex way therefore the combined toxic effect and interaction of the chemicals present can be expected and as a result the components can modify or even reinforce their toxic effects.
The aim of the examinations I carried out in this study was to explore the separate and combined harmful effects of the heavy metals (copper, cadmium, lead), which are dangerous for living creatures and can be found in our environment in greater quantities, and two kinds of widely used herbicide (Stomp 330 EC, Dikamin D) on embryos. The examination is suitable to observe how the toxic effects of pesticide affect developing bird embryos besides the load of heavy metals in our environment, if we examine the whole developing period of embryos. As the methods of eco-toxicological examinations are restricted to the examination of the toxic effect of only one pesticide, the data concerning the interactive effects of pesticide, especially in the organism of a developing bird, resolve discrepancies. This fact is very important because the prior and indispensable condition of
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the exploration and evaluation of the connection between living creatures and the environment is, to create exact data and data base that reinforce the results of research.
I used 1920 eggs of Shaver Rusticbro hens (Gallus gallus f. domestica) to carry out the experiments. After transportation and a 24-hour rest to follow I started to hatch the eggs. I chose the date of the treatment on the day of starting hatching, I introduced the materials of the experiment and their combinations into the eggs with a more provocative treatment of injection and dipping. The advantage of injection is that the material of experiment can be introduced into the required part of the egg at an exactly measured dose, while dipping introduces the chemical material into the egg similarly to exposition that occurs in reality. Before starting injection treatment I drilled a hole through the shell of the egg and then I introduced the materials of experiment into a 0.1-0.1 ml capacity. During dipping I put the eggs into a solution of 37C made from the materials of experiment and tap water or suspension for 30 minutes and after blotting the liquid I put them into the hatcher. Processing was carried out in two different points of time. On the second and third day of hatching I made germ disc cuttings from one part of the treated embryos in order to examine the early development stage. I processed the other treated two days before laying the eggs on the 19th day of hatching. I recorded the body weight of the embryos, the number and types of disorders and the number of deaths. In order to carry out histological analysis I took samples from the liver and long neck muscles of the embryos. I applied skeleton painting with the Dawson method to detect the possible developmental disorders of the skeleton. I applied Kolmogorov-Smirnov test to examine the distribution of body weight data, and as the data showed normal distribution I applied t-probe by Student for evaluation. I applied RXC Chi²-test to evaluate embryo mortality and developmental disorders statistically.
It can be concluded from the results of the examination of the early development of embryos that during the injection treatment the individual treatments resulted in only sporadic increase in the number of deaths and the occurrence of developmental disorders, comparing them to the control group, but in the case of the groups which were treated together Dikamin D and the heavy metals increased the deaths of embryos significantly. In the course of dipping treatments the occurrence of deaths and developmental disorders was only sporadic both in the groups which were treated individually or together. In the course of processing carried out on the 19th day of hatching the individual application of injection with heavy metals and pesticide increased the rate of death except for copper sulphate and also decreased the body weight of the embryos significantly. In the groups which were
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treated individually, the frequency of the occurrence of developmental disorders stayed at a medium level (2.17-18.42%). In the case of the groups which were treated together the death of the embryos increased clearly comparing it to the individual toxic effect of heavy metals and herbicide and the frequency of the deaths of the embryos was about 37-78%. In the groups which were treated with both Dikamin D and heavy metals the body weight of the embryos decreased significantly comparing it to both the control and the individually treated groups. The rate of developmental disorders also increased in these groups to the highest degree (18.7%-29.03%). In the course of processing on the 19th day of hatching dipping did not result in significant rate of deaths in the case of individual treatments, in the case of developmental disorders heavy metals caused significant deviation comparing it to the control group. However the decrease of body weight was significant in both individually treated groups. It can be concluded that in the groups which were treated together the deaths of embryos increased slightly comparing them to the individual toxic effects and developmental disorders also occurred more frequently during the interactive examinations than in the groups treated with only herbicide individually, which had a significant degree in the groups treated with both Dikamin D and lead acetate together, comparing them to the control group and the group treated individually with pesticide. The average of body weight decreased significantly in all cases comparing it to the control group and to the group which was treated individually with pesticide using Dikamin D, cadmium-sulphate, and lead-acetate together.
Disorders that can be shown by skeleton painting occurred only sporadically during the injection treatments in the individually treated groups except for Dikamin D, where 40% of the embryos indicated disorders. In the case of the groups that had a combined treatment the number of embryos with disorders did not increase significantly. The disorders of the neck and the legs and growth retardation were the characteristic features.
Comparing the injection treatment to the dipping treatment the latter caused fewer disorders, retardation occurred in the individually treated groups and the combined treatment did not increase the number of disorders significantly. As the effect of the dipping treatment the characteristic disorders were the faults of the neck and the legs.
The heavy metals and the herbicides did not cause disorders that could be shown in the histological samples of the embryos chosen at random with the technology of the light microscope, neither in the injection nor in the dipping treatment.
Comparing the results of the two treatments we can conclude that the more provoking injection treatment proved to be more toxic than the dipping treatment in the
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case of both the individual and combined treatments, which appeared in the increase of embryo deaths, the more frequent occurrence of developmental disorders, and the decrease of body weight, but the data of skeleton painting and the early examination of the embryos also show it.
The data we acquired during the experiment can help us understand that it is not enough to know chemicals on the basis of the examinations we need for the licence. Even the chemicals that we have been using for a long time can have effects that did not know in advance and the decrease of these unknown factors can make our environment more suitable for life and safer.
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