Radojica Đoković’s research while affiliated with University of Kragujevac and other places

Poultry farming on free-range can be organized in various ways, depending on the type and characteristics of facilities and outdoor areas. Generally, these rearing systems can be categorized into a fixed facility free-range system and a mobile facility free-range system (structures on wheels). In organic poultry production, two organic production systems are prevalent: organic egg production and organic meat production.

Cow's milk contains a large number of fatty acids, some of which may be of potential benefit to human health. The aim of this research is to determine the most important biological and ecological factors that influence the fatty acid composition and nutritional indices of raw milk originating from cows in intensive farm production. Comparing to reference cows, next animals had significantly higher odds of having greater SFA concentrations and lower odds of being in the categories with higher MUFA, PUFA and UFA and concentrations in milk: cows in 2nd and 3rd lactation compared to 1st, cows in mid and late lactation compared to early, cows in heat stress compared to cows in thermoneutral period. Comparing to reference cows, cows with higher BHB had significantly lower odds of having greater SFA concentrations and higher odds of being in the categories with higher MUFA. Also, cows with higher NEFA had significantly lower odds of having greater SFA concentrations and higher odds of being in the categories with higher PUFA. In experimental group compared to reference we found lower odds of having greater nutrition index of milk. Odds to have higher nutrition index increase in cows with intense ketogenesis and lipolysis. In conclusion, older cows, cows in an advanced stage of lactation and cows in heat stress have higher values of SFA, while cows with higher lipolysis and ketogenesis have higher contents of MUFA, PUFA and UFA, which leads to a change in the nutritional indices of raw milk.

Heat shock proteins (Hsp), also called chaperones, are proteins that are indispensable for the proper formation of the polypeptide chain; and have a role in its translocation within the cell. Hsp70 in cells helps to re-establish the native conformation of proteins that have denatured under the influence of various stressogens, by preventing their aggregation, which results in protecting the cell from apoptosis and having an anti-inflammatory effect. These proteins are classified on the basis of molecular mass, and the most significant is heat shock protein 70 (Hsp70) with a molecular mass of about 70 kDa, which is designated as "a master player in protein homeostasis". The concentration of Hsp increases significantly when exposed to a stressor originating from the cell itself or from the external environment. Many chaperones are induced under the influence of high ambient temperatures, when the universal heat shock response (HSR) develops, which is why the name heat shock proteins was defined. Intracellular Hsp70 (iHsp70) shows its protective and anti-inflammatory effects. Induced iHsp70 protects the cell from apoptosis by reducing or blocking the activation of caspases, binding to apoptosis-inducing factor (AIF) and inhibiting AIF-induced chromatin condensation or preventing mitochondrial damage and nuclear fragmentation. It blocks cell morphological changes caused by tumor necrosis factor-induced apoptosis, and has been found to aid in cell repair of damage caused by inflammation. The anti-inflammatory effect of iHsp70 is reflected in the fact that it inhibits the response to lipopolysaccharides and blocks the production of inflammatory mediators such as tumor necrosis factor Alpha (TNF-a), and other mechanisms have been described. he expression of the gene for the production of Hsp70 has been well studied in ruminants or their cell cultures exposed to high ambient temperatures, and the multiple increase of iHsp70 in the cells results in a better adaptation to heat stress. The study of eHsp70 has become relevant due to the availability of diagnostic kits for determining its concentration, and the latest results show that it is a very useful predictor of mortality in patients with septic shock. Hsp70 moves to the extracellular space in several ways: after leaving necrotic cells, under the action of various stress factors and inflammation in undamaged cells, it can be produced in the liver as an acute phase protein, and transport by exosomes and direct contact with the lipid membrane of cells have also been described. The pro-inflammatory effect of eHsp70 is realized by inducing immune cells, which further induces the secretion of inflammatory cytokines (TNF-a, IL-1b, IL-6), inducible nitric oxide synthase (iNOS) expression and nuclear translocation of nuclear factor-cB (NF-cB). According to the chaperone balance theory, the higher the value of eHsp70 compared to iHsp70, the more pronounced its proinflammatory effects. This hypothesis was also confirmed in dairy cows in the periparturient period.

In recent years, numerous papers have been published that consider indicators of cattle and pig farms biosecurity with the aim of improving it, and therefore their health and productivity. These indicators were presented in international projects published in indexed journals, as well as proceedings from international symposia. On-farm assessments usability of farm production biosecurity is generally well recognized. In the assessments of the farm biosecurity in different systems of rearing and accommodation, the need to determine new indicators in cattle and pig production was observed and discussed, based on a meta-analysis of previously published studies which include the most important papers in indexed journals and proceedings from international symposia that discussed the existing indicators. The analysis of the results of those studies will be used to determine the main characteristics of the existing new farm biosecurity indicators on cattle and pig farms with a focus on their applicability. The results, discussions and conclusions of those papers will be used to generate ideas to define biosecurity indicators on cattle and pig farms.

In recent years, numerous papers have been published that consider indicators of the welfare and stress of the animals on cattle and pig farms to improve their health and productivity. These indicators are mostly determined in numerous international projects and published in indexed journals and proceedings from international symposia. Their usefulness in on-farm assessments of animal welfare and stress is generally well recognized. In the assessments of the welfare and stress of the animals in different systems of rearing and accommodation, the need to determine new welfare and stress indicators on cattle and pig farms was observed. The paper discusses the determination of new indicators of animal welfare and stress on cattle and pig farms based on analysis of previously published studies which include the most important papers in indexed journals and proceedings from international symposia that discussed the existing indicators. The analysis of the results of those studies will be used to determine the main characteristics of the existing new welfare and stress indicators on cattle and pig farms with a focus on their applicability. The results, discussions and conclusions in those papers will be used to generate ideas to define new welfare and stress indicators of the animals on cattle and pig farms.

Pooled blood samples are an economical and high-quality way to show the state of a certain population, as well as the response of the population to certain factors of the external and internal environment, the use of pooled blood samples in veterinary medicine and related fields has found wide application, whether it is for the diagnosis of infectious diseases , the use of samples in internal quality control in the laboratory or in the diagnosis of various diseases. Creating a pooled blood sample saves time and reduces the cost of analysis, and enables easier storage of the sample, while individual samples require greater space, time and financial resources, with a greater source of errors. In the analytical sense, a larger volume of the collective sample (made up of a small volume of a larger number of samples) of blood enables a better determination of the detection limit, while in the case of individual samples, a sufficiently large amount of that one sample must be provided. Statistically estimable also differs, so with a pooled blood sample we can estimate the mean, but not the variability as in a population of individual samples. As a general rule, the mean value of the collected samples should be close to the middle of the reference range to be considered normal. The criteria for the interpretation of mean values have not been fully defined. It is considered that the mean value obtained should be in the range of 1 or 1.3 standard deviations in the reference population in order to be able to conclude that there are no individuals with significant metabolic problems. It was found that if there are up to 10% of abnormal metabolic values in the population, we will have a small deviation of the pool value from the population mean, which will amount to about 0.26 standard deviations, but that it largely depends on the analyte being measured. Our results showed that the average value of individual blood samples and the concentration obtained by pooling those individual samples give almost identical values that change identically as a function of the lactation period and the health of the cows. Due to all of the above, the preparation of pooled samples can be an interesting tool in the evaluation of the metabolic profile of larger cow populations.

Research on the impact of heat stress on animals has mainly been related to cattle, while sheep have been neglected and the impact of heat stress on sheep production is still insufficiently researched. There are numerous stressors related to the procedures and methods of breeding sheep in barns and pastures among them ambient temperature is the most important variable because its effect is exacerbated in the presence of high humidity. Thermal indices are useful for assessing the influence of weather parameters in a certain agroecological area, of which the temperature-humidity index proved to be the best thermal index for assessing the harmful effect of heat stress on the productive performance of animals. Sheep have good adaptability and they are resistant to harsh environmental conditions, still in addition to a certain tolerance to heat stress, high temperatures can negatively affect sheep, which most often leads to dehydration, reduced appetite, reduced milk production and increased risk of disease. Mechanisms that help sheep to survive the challenge of heat stress include morphological, behavioural, physiological, blood biochemistry and genetic bases of adaptation. Sheep can combat heat stress by seeking shade, drinking enough water, and properly ventilating the barn. Increasing the productivity of sheep by adapting various management strategies including housing and animal management and climate monitoring may enhance production capacity of the herd. Therefore, heat stress has a negative effect on sheep, temperatures will increase year by year, and therefore it is necessary to investigate the relationship between sheep production and heat stress in time, to improve sheep farming and make life easier in the days ahead.

Increasing milking frequency can increase milk production in cows by 15-20%, and increased milking frequency can affect different mechanisms of secretion and metabolic activity of the udder. In practice, cows are best milked twice a day with an average interval between two milkings of 12 hours, and in practice it is the most common range of 8-16 hours. It was shown that a 12-hour interval between two milkings was good for high-yielding cows, with a steady increase in milk production during the first half of lactation. An extended interval between two milkings will lead to inhibition of lactation with a consequent decrease in the amount of milk produced. Increasing the milking frequency of dairy cattle to more than two milkings per day results in an increase in milk production. Milking three times a day leads to an increase in milk production of 3 to 39% compared to milking twice. One of the most obvious effects as a result of increased milking frequency is the mobilization of body reserves. The primary mechanism leading to this is lipolysis. As a result of lipolysis, there is an increase in the concentration of NEFA and BHB in the blood plasma or serum with a decrease in the assessed body condition of the cows, and the mentioned changes are considered a typical response to an increase in milking frequency. The tests showed a significant decrease in the body condition score in cows that were milked six times compared to cows that were milked three times. Increased lipolysis and ketogenesis lead to a metabolic response and adaptation of cows, and these changes can sometimes lead to an increase in metabolic diseases in cow herds.

Hormones are very important in cows because they participate in the orchestrated rearrangement of the organism for the coming lactation (homeoresis) and as such have great diagnostic and prognostic significance, so maintaining their stability in the sample is of crucial importance. Three hundred samples originating from dairy cows in different periods of lactation participated in this research. The samples were divided into 6 groups: according to the time from sampling to processing in the laboratory (0-4h, 4-8h and over 8h) and according to the presence of pre-analytical factors (group with hemolysis, group transported at ambient temperature and group with small sample volume). he samples were left at +4°C and were tested once a day during 6 days of sample storage. Samples that were placed at -20°C were tested once a month for 6 months. The maximum permissible instability calculated on the basis of analytical and intraindividual variability ranged from 6.2 to 6.8 % (T3, T4, STH. IGF-I and progesterone) and up to 7.1 to 7.2 % (for insulin and cortisol) and it is considered that the sample has lost its stability if during the time there is a change in the value of the parameters in a percentage above this maximum determined value. The lowest stability at +4°C was shown by progesterone, which can be stored for up to 48 hours. Next was insulin, which can be stable for up to 3 days in a sample affected by preanalytical errors, but was more stable in samples not affected by preanalytical errors. Cortisol, T3 and T4 have less stability and can be stored for up to 4 or 5 days if the sample is loaded with pre-analytical errors. With frozen samples, no significant decrease in stability was found during the experimental period. The stability of endocrinological parameters is influenced by the properties of hormones and the existence of pre-analytical errors in the test tube.

The aim of the present study was to determine a correlation between blood concentration of lipids and the content of lipids in the liver of dairy cows in the transitional period. The Holstein dairy cows (n = 40) were divided into four groups: the first group (A) included late pregnant cows (n = 10) from the 10th to 4th day before calving; the second group (B) included late pregnant cows (n = 10) from the 4th to 1st day before calving; the third group (C) included clinically puerperal healthy cows (n = 10), whereas the fourth group (D) included puerperal ketotic cows (n = 10). The liver and blood samples were taken from all the cows. Pathohistological examination of liver samples showed statistically significantly higher (p < 0.01) lipid infiltration in ketotic cows compared to healthy cows in late pregnancy and puerperium. Biochemical examination of blood serum showed significantly higher values (p < 0.01) of nonesterified fatty acids (NEFA) and beta-hydroxybutyrate (BHB) in ketotic cows, such as lower blood concentrations of glucose (p < 0.01), triacylglycerols (TG) (p < 0.01), and total cholesterol TChol. (p > 0.05) compared to the values obtained in the blood serum in the groups of healthy cows before and after calving. The significantly positive correlations were determined between the content of lipids in the liver and blood concentration of NEFA (r = 0.67; p < 0.05) and BHB (r = 0.55; p < 0.05) as well as the negative ones between the content of lipids in the liver and blood concentrations of glucose (r = -0.45; p < 0.05), TG (r = -0.55; p < 0.05) and TChlol. (r = - 0.39; p < 0.05). Our investigations suggested that changes in the blood concentrations of NEFA, BHB, TG, TChol. and glucose served as major biochemical indicators in determining ketosis and liver steatosis in the dairy cows in the transitional period.