Bienestar animal en plantas faenadoras: situacin actual en la Argentina
There are multiple aspects that affect animal welfare in production systems\nincluding environmental factors and those related to management conditions.\nRegarding the latter and considering that one of the goals of the production sector is the improvement of efficiency levels, one of the alternativ...
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| Formato: | Tesis doctoral acceptedVersion |
| Lenguaje: | Español |
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Universidad de Buenos Aires. Facultad de Ciencias Veterinarias
2023
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=avaposgra&cl=CL1&d=HWA_7538 https://repositoriouba.sisbi.uba.ar/gsdl/collect/avaposgra/index/assoc/HWA_7538.dir/7538.PDF |
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| Sumario: | There are multiple aspects that affect animal welfare in production systems\nincluding environmental factors and those related to management conditions.\nRegarding the latter and considering that one of the goals of the production sector is the improvement of efficiency levels, one of the alternatives would be to have young bulls capable of naturally synthesizing anabolic hormones such as testosterone. Focusing on environmental aspects, heat stress is one of the main issues in cattle. Although cattle can adapt to a wide range of thermal environments, both\nextreme and sudden fluctuations in temperature can cause heat stress. If unable to cope with these events, animals can suffer consequences where physiology, behavior\nand health are strongly affected by the excessive heat load modifying their well-being, which in the worst case can result in death. Therefore, the provision of shade\nrepresents one of the resources to be used as a strategy to mitigate heat stress by modifying the microenvironment. Shade resource in order to modify the microenvironment represents a strategy to mitigate heat stress.\nTo address both problems, two experiments were carried out in this thesis to\nstudy the effect of: a) slaughter category and breed, and b) the use of shade during a period of high risk of heat stress, over variables associated with animal welfare in cattle.\nThe first experiment was implemented in a livestock establishment located in\nRosario de Lerma, Salta. For this purpose, 128 animals (9 months, 238 ± 4 kg) were\nrandomly selected from the herd in order to evaluate the effect of category (young bull\nvs. steer) and breed (Black Angus vs. Brangus) over welfare. Before the fattening\nstage, half of the animals of each breed group were castrated by the same personnel of the establishment, without resorting to the use of anesthesia or analgesia. After 180 days of fattening, the animals were transported to the slaughterhouse at a distance of 500 m from the farm.\nUnder the conditions where the trial was carried out, young bulls presented lower\nvalues (p < 0.05) of visual exit velocity score, higher levels of daily live weight gain, carcass yield and meat yield in 6 of the 11 meat cuts evaluated. Meat from these\nanimals showed higher ultimate pH levels, both darker and less red coloration, higher\nlevels of water holding capacity and tenderness compared to the values observed in steers (p < 0.05). The type of pre-slaughter management, as well as the lower level of\nfattening of the non-castrated males could be responsible for the results obtained. On the other hand, a higher level of carcass yield was observed in Brangus cattle\ncompared to Angus, while young Brangus bulls presented the lowest levels of reactivity score (p < 0.05). No significant relationship (p > 0.05) was found between the temperament exhibited by the cattle and the productive, physiological and meat quality ariables.\nThe second experiment was conducted in a commercial feedlot located in San\nAgustín, Córdoba, from December 2016 to February 2017 (82 days duration). In order to evaluate the effect of shade resource (with shade: 3.3 m2 of shade/animal vs.\nwithout shade), 90 British and Indica crossbred cattle were randomly selected per\ntreatment. Considering the conditions under which the study was conducted, shade\nprovision had an effect on certain variables. Under microclimates where the thermal index was categorized as "warm" or higher, the provision of shade resulted in a\ndecrease in panting score and changes in maintenance behavior (p < 0.05), the latter mainly expressed by the proportion of animals spending time lying or standing, which\ndepended on the time of day. In addition, lower hematocrit values (p < 0.05) and a tendency to lower total protein values were observed in animals that were provided with shade.\nThe relationship between the use of shade and increased severity of climatic\nconditions resulted in a higher percentage of cattle being able to spend time resting by lying behavior. Among animals deprived of the shade resource, a higher proportion remained standing to minimize the body surface area in contact with the ground. The\nprovision of shade had no effect over weight gain, carcass weight, erformance, health and cortisol levels (p > 0.05). Considering these results, it is possible that according to the degree of severity of the climatic conditions exhibited during the experimental\nperiod, the provision of shade might have had a positive impact on behavior and certain physiological variables, without generating modifications in the rest of the variables, which would be determined by the total number of hours of high\ntemperatures that cattle cope with heat stress.\nBased on the findings of this thesis, it can be concluded that the management\nconditions within beef livestock systems have a direct impact on behavioral indicators. These indicators are closely associated with specific factors such as animal stress levels, quantity, and meat quality variables. In future studies, it would be valuable to\nfurther investigate the effect of different management procedures on temperament.\nAdditionally, exploring the relationship between temperament and performance, as well\nas physiological and meat quality variables in steers and young bulls, would be of great interest. It is crucial to consider alternative methods that minimize stress during\nzootechnical practices like castration. In addition, it is proposed to evaluate the\neffectiveness of different strategies to mitigate heat load on animal welfare,\nperformance and meat quality variables focused particularly in feedlots located in areas\nat higher risk of heat stress. By addressing these topics, we can enhance our\nunderstanding of how management practices influence animal welfare and, consequently, the overall quality of beef |
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