Andmebaasi logo

Sirvi Autor "Kaart, Tanel (advisor)" järgi

Nüüd näidatakse 1 - 4 4
  • Pisipilt
    Kirje
    Genetic and modelling aspects of milk coagulation properties in dairy cattle
    (Eesti Maaülikool, 2013) Vallas, Mirjam; Pärna, Elli (advisor); Pärna, Kalev (advisor); Kaart, Tanel (advisor); Arney, David; Rand, Nele
    Milk coagulation properties (milk coagulation time and curd firmness) are of great importance for the cheese industry because of their influence on cheese outcome and quality. This thesis focuses on possibilities for the genetic improvement of these economically important traits in Estonian Holstein cattle and also evaluates transformation possibilities of milk coagulation measurements into one scale, between different analytical techniques. This study is the first large-scale study of genetic parameters of milk coagulation traits based on the optical method for measuring these traits. Estimates of heritability, repeatability and genetic correlations among milk coagulation, production, milk fat and protein percentage, somatic cell score, urea content and pH were found. Effect of β-κ-casein genotype on the milk traits referred to above and their additive genetic variation were also examined. Genetic parameters were estimated based on 17,577 first lactation milk samples from 4,191 Estonian Holstein cows, while β-κ-casein genotype effects were evaluated based on 23,970 milk samples for the first to third lactation from 2,859 genotyped Estonian Holstein cows. To study the transformability of measurements of milk coagulation traits, these traits were measured for 165 milk samples in two laboratories in Italy, using two different mechanical methods, and in Estonian laboratory using the optical method. The analyses of subsamples from the same cow were performed on the same day in all three laboratories. The study revealed that precision of transformation was high for milk coagulation time, while transformability of curd firmness remained moderate between mechanical methods, and modest between optical and mechanical methods. The association between milk coagulation traits, measured by the optical method, and cheese outcome and quality remains unclear. Genetic study showed that heritable additive genetic variation described about one-third of the phenotypic variation in milk coagulation traits of Estonian Holstein cows. Further, the β-κ-casein genotype described half of the additive genetic variation of curd firmness. Genetic associations of milk coagulation traits with milk production, pH and composition traits were predominantly low and favourable. It could be concluded that genetic determination of milk coagulation traits enables the improvement of these milk properties by using breeding methods, such as direct selection, on these traits as well as selection on the basis of genetic markers considering the high frequency found for β-κ-casein genotypes with an unfavourable effect on milk coagulation properties. However, a lack of high capacity equipment and analytical techniques for measuring milk coagulation traits makes routine recording of these traits on a whole dairy cow population unfeasible. Nevertheless, genetic evaluation can be applied to a limited number of breeding animals (e. g. bulls or bull dams).
  • Pisipilt
    Kirje
    Impact of climate change and other ecological factors on selected fish populations and fishery in Estonian large lakes
    (Eesti Maaülikool, 2021) Öğlü, Burak; Kaart, Tanel (advisor); Kangur, Külli (advisor); Cremona, Fabien (advisor); Kuparinen, Anna (opponent); Olli, Kalle (pre-opponent)
    Human activities and climate change have become the most consequential threats to freshwater ecosystems and their inhabitants, especially fish. The response of the fish population to their environment is not always straightforward because of joint effect of multiple parameters. Fish and fisheries in shallow lakes can be directly affected by changes in air temperature, and also changes can occur via other factors in lakes that are under the influence of climate change. Also, response of each fish species to those parameters can vary depending on their tolerance and adaptation. Therefore, examining complex relationships between fish and their environment plays important role at understanding the dynamic of fish population and fisheries. In this study, we aimed to determine general driving factors, including climate change impact, for fish and fishery in Estonian large lakes. Results show that although winter is one of the most affected seasons by climate change in this region, then the selected fish species and eel fishery in Estonian large lakes were more sensitive to other environmental parameters. However, since the changes in winter surface water temperature and ice formation can affect other parameters, the indirect effect should not be ignored. Nutrients, spring-summer temperature and alkalinity were the most important environmental parameters for the selected fish biomass. We found that the high blue-green algae biomass during restocking period is the strongest negative impact for the eel fishery in Lake Võrtsjärv. The impact of factors can occur subsequently in fish communities and may lead to irreversible consequences, whereas the effects of concurrent climate change and nutrient enrichment can mutually reinforce their symptoms.
  • Pisipilt
    Kirje
    Regrouping effects on behaviour and welfare of dairy cows
    (Eesti Maaülikool, 2021) Soonberg, Maria; Arney, David (advisor); Kass, Marko (advisor); Kaart, Tanel (advisor); Raussi, Satu (opponent)
    Animal welfare is a concern for many people around the world and it is believed by consumers that higher welfare standards on farms will ensure high quality, healthy and safe food. Precision livestock farming is becoming more popular and feeding management systems have changed accordingly. The aim of this study was to evaluate the effect such changes in farm management have on cows’ behaviour and welfare. Cows activity (I, III), feeding, aggressive (II, III) and social behaviour were assessed to see how grouping affects cows at different ages, milk yields (high and low yielding cows) and during the transition period. Cows in study I and III had activity monitors attached to their hind legs to measure their activity, in studies II and III feeding and aggressive behaviours were measured with video cameras, and in study III social behaviour was measured visually by recording sample cows’ two closest neighbours. It was concluded that when cows feeding place changes (because of grouping) their activity will increase. For primiparous cows this increase was by a factor of 1.44 and for multiparous cows 0.36. When cows were moved to a dried off group their activity increased at first, but in general it was lower in the dried off area than in the main herd. In study II high and low yielding cows forage feeding time was assessed. High yielding cows received extra concentrate from a concentrate feeder. Low yielding cows did not. No statistical difference was found between those two groups for forage feeding times. Neither the feeding, walking, standing nor drinking times were significantly affected by additional feeding of concentrates. In study III cows were found to be more active after calving compared to before calving. The cows, who were more aggressive in cubicles were also more aggressive in the strawyard (P = 0.033). Heifers received more aggressive acts than cows (P < 0.001). Sample cows distance to their closest nearest neighbour was one meter, and second nearest neighbour was 0.15 m further away in the cubicle housing compared to the strawyard. After calving, when cows were sent to main herd, primiparous cows spent less time feeding (mean time cow was recorded feeding 9.0%) than multiparous cows (mean time cow was recorded feeding 31.7%)(P = 0.042), especially on the first day in the main herd and they were observed in the passageway more often than the multiparous cows. It was concluded that activity, aggression and social bonds are affected by grouping. Knowing this, farmers can plan their farm management system so that cows can be grouped and regrouped less often. This would help cows to have stronger social relationships, experience fewer aggressive encounters and in general have a more stress free life.
  • Pisipilt
    Kirje
    Relationship between bovine colostrum particle size and composition
    (Estonian University of Life Sciences, 2024) Sats, Andres; Jõudu, Ivi (advisor); Kaart, Tanel (advisor); Lepasalu, Lembit (advisor); Institute of Veterinary Medicine and Animal Sciences; Gross, Josef Johann (opponent)
    ABSTRACT. Colostrum is one of the by-products associated with milk production. Bovine colostrum, as a source of bioactive and functional components, has been studied for decades. When developing and optimizing processing technologies, it is necessary to consider various parameters, including particle size distribution and related factors. This work aimed to fill the knowledge gaps regarding the size distribution of colostrum particles. Additionally, the relationships between particle size, colostrum composition, and some animal-specific characteristics were investigated. The diameter of fat globules in colostrum doubles during the first four consecutive milkings. The fatty acid profile in the first three milkings is similar, but differs noticeably from the fourth milking. Colostrum collected from the fourth milking onwards can be considered as transitional milk. The size of whey particles in colostrum decreases during four succeeding postpartum milkings. The size distribution of whey particles, along with immunoglobulin G (IgG) content results, indicates that a 100 nm (filter)pore size is sufficient for separating IgG particles of approximately 10 nm in diameter. Similarly, the content of casein and the diameter of casein micelles decrease during the first four postpartum milkings, but the latter remains larger than described in regular milk. Gaining knowledge about the alterations in bovine colostrum, with a particular focus on particles size distribution, is essential for both research and practical applications. Knowledge of the dynamics of casein micelle size distribution in colostrum can contribute to a better understanding of casein micelle formation mechanisms and functionality. Moreover, the collected information provides opportunities for optimizing existing colostrum valorization technologies in a more environmentally sustainable way and for developing new technologies that preserve the bioactivity and nutritional value of colostrum components.