No presente trabalho foi avaliada a técnica de ultra-sonografia em tempo real como ferramenta para predição da área de olho-de-lombo (AOL) e espessura da camada de gordura subcutânea (ECG) a partir de imagens tomadas em animais vivos. Foram utilizados 115 bovinos jovens (30 ½ Angus x Nelore; 30 ½ Canchim x Nelore; 30 ½ Simental x Nelore e 25 Nelores), peso inicial médio de 329 kg, de dois tamanhos à maturidade (pequeno e grande) no sistema de produção do novilho superprecoce. As medidas de ultra-sonografia foram realizadas a cada 28 dias totalizando quatro medições até o final do confinamento. Os resultados obtidos demonstraram que a precisão da predição aumentou em função da proximidade com a data do abate, sendo máxima na quarta medida (R 2 de 0,68 para AOL e 0,82 para ECG com as mesmas medidas na carcaça). O efeito de grupo genético e as medidas ultra-sonográficas foram significativos (P<0,05) para ECG, enquanto que na carcaça ambas medidas foram significativas. A AOL da ultra-sonografia por 100 kilogramas (kg) de peso vivo (AOL4PKG) foi significativamente (P<0,05) influenciada pelo grupo genético, mas não pelo tamanho corporal. Em relação à AOL da carcaça por 100 kg de carcaça (AOLPCAR), todos os grupos genéticos alcançaram o valor ideal apontado pela literatura como indicativo de bom rendimento de cortes cárneos. Não foi observada diferença significativa (P<0,05) na composição entre os dois grupos de tamanho corporal provavelmente devido à pequena variação existente entre eles. Os mestiços Simental apresentaram a maior porcentagem de músculo na carcaça, e os animais Nelore o menor valor (P<0,05). Os animais Nelore, mestiços Canchim e Angus tenderam a acumular maior porcentagem de gordura na carcaça quando comparados aos mestiços Simental (P<0,05). A AOL por ultra-sonografia apresentou correlações positivas com a quantidade de músculo (0,49), de cortes cárneos (0,42) e porcentagem de tecido muscular estimada da carcaça (0,30). A ECG por ultra-som foi positivamente correlacionada com a porcentagem (0,49) e a quantidade de tecido adiposo estimada na carcaça (0,52), e negativamente correlacionada com a porcentagem de traseiro (-0,49). O rendimento de cortes cárneos só apresentou correlações significativas com a medida de AOLPCAR (0,26), o peso vivo dos animais (-0,45) e o peso da carcaça quente (-0,44). As medidas ultra-sonográficas nos animais vivos não mostraram alta precisão na predição da AOL na carcaça. Em geral os coeficientes de determinação das equações regressão para predição das características da composição da carcaça pelas medidas ultra-sonográficas são similares ou superiores àqueles obtidos nas equações que utilizaram as mesmas medidas após o abate. Este fato indica que o erro na predição da AOL não necessariamente se deve a uma falha na técnica de ultra-sonografia, mas também pode ser causada por diferenças naturais entre as medidas tomadas na carcaça e no animal vivo. / In the present study real time ultrasonography was used to predict the ribeye area (AOL) and the subcutaneous fat thickness (ECG) in live animals. A total of 115 yearling steers from four genetic groups (30 ½ Angus x Nelore; 30 ½ Canchim x Nelore; 30 ½ Simental x Nelore e 25 Nelores), with 329 kg initial average weight, and two different finishing frame sizes (small and large) were used. Animals were kept in a feedlot during the whole study. Four ultrasonographic measurements were taken every 28 days until slaughter. AOL and ECG were measured in the carcasses and compared to the measurements made in the live animals. Predictive accuracy of the ultrasonographic measurements increased as the animals approached slaughter date, reaching the maximum value at the last one (R 2 = 0.68 and 0.82 for AOL and ECG, respectively). Genetic group influenced (P<0.05) AOL and ECG measurements in the carcass but only the ECG was significant with the ultrasound (P<0.05). AOL ultrasonographic measurements showed a significant difference (P<0.05) among the genetic groups when body weight (per 100 Kg of carcass) was taken into account (AOL4PKG). AOL per 100 kg of carcass (AOLPCAR) for all genetic groups showed higher values than those suggested by the literature. Frame size did not influence AOL or ECG probably due to the small, but distinctive differences between the two groups. The Simental crossed animals had higher (P<0.05) carcass muscle percentage, and the Nelore steers had the lowest. The Nelore, Canchim and Angus crossed animals showed higher carcass fattissue percentage (P<0.05) as compared to the Simental crosses. The ultrasound AOL showed a positive correlation (0.49) with muscle weight, carcass cutability (0.42) and muscle carcass percentage (0.30). The ultrasound ECG was positively correlated with fattissue percentage (0.49) and carcass total fat tissue amount (0.52) and negatively correlated with the hind cut yield (-0.49). Carcass meat yield was correlated only with AOLPCAR (0,26), live weight (-0.45) and hot carcass weight (0.44). The ultrasound AOL had a low prediction accuracy for the carcass AOL. Overall, the accuracy of the carcass composition’s predictive equations by ultrasound were similar or greater than the one obtained by direct carcass measurements. This suggests that the difference in AOL measurements by ultrasonography and in the carcass does not necessarily mean a faulty ultrasonographic measurement for differences can be expected when measurements are made in the carcass or in the live animal.

O atropelamento de animais silvestres é considerado como o principal fator antrópico responsável diretamente pela mortalidade de vertebrados terrestres em escala global. Estimativas de mortalidade são fundamentais para avaliar o impacto de rodovias, mas para reduzir o seu viés a remoção de carcaças e a eficiência dos observadores devem ser consideradas. Medidas mitigadoras têm sido implementadas para reduzir a mortalidade da fauna e ampliar a conectividade da paisagem, mas um fator determinante para a sua efetividade é a sua correta localização. Com o objetivo de qualificar o planejamento de medidas mitigadoras, neste trabalho procuramos responder a quatro perguntas: 1) há diferença na remoção e detectabilidade de carcaças entre diferentes grupos taxonômicos? 2) qual a influência da remoção e detectabilidade de carcaças sobre as estimativas de magnitude de mortalidade? 3) a mortalidade se distribui de forma agregada ao longo da rodovia? e 4) a distribuição espacial de atropelamentos de diferentes grupos taxonômicos é similar? Nossos resultados apontam diferenças na taxa de remoção e na detectabilidade de carcaças entre os grupos, além de demonstrar que, ao desconsiderar esses fatores, a magnitude de atropelamentos é subestimada. Ademais, nossos resultados indicam que a distribuição espacial de atropelamentos de mamíferos pode ser utilizada como indicadora da ocorrência de atropelamentos de outros grupos taxonômicos apenas em escalas menos refinadas, exigindo o planejamento de medidas mitigadoras mais amplas. Os resultados aqui apresentados devem ser considerados no monitoramento de animais atropelados e no planejamento de medidas mitigadoras do impacto de rodovias. / Vehicle-wildlife collisions are considered the main human factor responsible directly for vertebrate mortality worldwide. Roadkill estimates are elementary to evaluate road impacts, but carcass removal and searcher efficiency must be considered in order to diminish estimation bias. Mitigation measures have been implemented to reduce wildlife mortality and to increase connectivity, but their correct placement is an important factor defining the effectiveness of these measures. In order to qualify mitigation planning, in this study we aim to answer four main questions: 1) is there difference in carcass removal rates and detectability among different taxonomic groups? 2) do carcass removal and detectability influence mortality magnitude estimates? 3) are roadkills spatially aggregated? and 4) are roadkill spatial distribution of different taxonomic groups similar? Our results show differences in carcass removal and detectability among groups, and demonstrate that mortality magnitude is underestimated when these factors are not considered. Also, our results indicate that mammal roadkill aggregations may be used as a surrogate of roadkill aggregations of other taxonomic groups in larger scales. The results presented here must be considered in roadkill monitoring and in mitigation measures planning.

Foram realizadas mensurações dos rins direito e esquerdo, bem como, de carcaças de bovinos Nelore, inteiros e castrados. As médias gerais dos grupos e os respectivos desvio padrão para as mensurações renais foram: comprimento do rim direito 16,85 &plusmn; 1,10 cm; comprimento do rim esquerdo 16,20 &plusmn; 1,15 cm. As larguras dos rins direito e esquerdo apresentaram médias e desvio padrão iguais a 9,20 &plusmn; 0,80 cm e 9,35 &plusmn; 0,90 cm, respectivamente. Para a variável peso dos rins direito e esquerdo, as médias e desvio padrão foram, respectivamente, de 347,90 Kg &plusmn; 32,55 Kg e 343,25 Kg &plusmn; 32,20 Kg. O número de lobos observados nos rins direito e esquerdo obtiveram médias e desvio padrão de 16,30 &plusmn; 4,50 e 15,90 &plusmn; 3,90, respectivamente. Para as variáveis de carcaça dos grupos envolvidos as médias e respectivos desvios padrão foram: para peso das hemicarcaças direita e esquerda 137,00 &plusmn; 8,00 e 141,10 &plusmn; 8,00 Kg; peso total da carcaça 278,10 &plusmn; 15,90 Kg; rendimento de carcaça 55,80 &plusmn; 1,30%; espessura de gordura 6,30 &plusmn; 2,6 cm; comprimento de carcaça 1,28 &plusmn; 0,03 m. Para comparação das diferentes mensurações, os animais foram divididos em dois grupos (inteiros e castrados). Diferenças significativas (P < 0,01) foram observadas para quase todas as variáveis de carcaça exceto para comprimento da mesma. Para as variáveis de rim, resultados significativos foram observados para largura de rim direito (P < 0,01), peso de rim direito, peso de rim esquerdo e peso total dos rins (P < 0,05). As estimativas de correlações entre todas as características foram de baixa magnitude, indicando ausência de associação entre as diferentes medidas. / Measurement of the right and left kidneys were accomplished, non castrated and castrated carcasses of bovine Nelore. The averages managed of the groups and the respective deviation pattern for the renal measurement were: length of the right kidney 16.85 ± 1.10 cm, respectively; length of the left kidney 16.20 ± 1.15 cm. The widths of the kidneys right and left presented averages and standard deviation to 9.20 ± 0.80 cm and 9.35 ± 0.90 cm, respectively. For the variable weight of the kidneys right and left, the averages and standard deviation were, respectively, of 347.90 Kg ± 32.55 Kg and 343.25 Kg ± 32.20 Kg. The number of lobes observed in the kidneys right and left obtained averages and standard deviation of 16.30 ± 4.50 and 15.90 ± 3.90, respectively. The averages and respective deviation pattern of variables of the involved groups for carcass were: for weight of right and left hemicarcass 137.00 ± 8.00 and 141.10 ± 8.00 Kg total weight of the carcass 278.10 ± 15.90 Kg; carcass exploitation 55.80 ± 1.30%; fat thickness 6.30 ± 2.6 cm, carcass length 1.28 ± 0.03 m. For comparison of the different measurement, the animals were divided in two groups (non castrated and castrated). Significant differences (P <0,01) were observed for almost all the carcass variables except for length. For kidney variables, significant results were observed for width of right kidney (P <0,01), weight of right kidney, weight of left kidney and total weight of kidneys (P <0,05). The estimates of correlations among all the characteristics were of low magnitude, indicating association absence among the different measures.

O objetivo deste estudo foi avaliar o desempenho produtivo, o rendimento de carcaça e de cortes comerciais de frango alimentados com rações peletizadas contendo diferentes relações de valina/isoleucina durante as fases de crescimento e final (22 a 42 dias) desses animais. Foram utilizados 630 pintos machos de um dia de idade, da linhagem cobb 500. De 1 a 22 dias de idade, todas as aves receberam uma ração basal comum e aos 22 dias foram pesadas e distribuídas em um delineamento inteiramente casualizado, em esquema fatorial 3x3 (nove combinações de níveis de valina e isoleucina). Os frangos de corte foram submetidos aos seguintes tratamentos experimentais: T1 ração com relação valina/lisina 0,75% e isoleucina/lisina de 0,67%; T2 ração com relação valina/lisina 0,75% e isoleucina/lisina 0,71%; T3 ração com relação valina/lisina de 0,75% e isoleucina/lisina de 0,75%; T4 ração com relação valina/lisina de 0,79% e isoleucina/lisina 0,67%; T5 ração com relação valina/isoleucina de 0,79% e isoleucina/lisina 0,71%; T6 - ração com relação valina/isoleucina de 0,79% e isoleucina/lisina 0,75%; T7 - ração com relação valina/isoleucina de 0,83% e isoleucina/lisina 0,67%; T8 - ração com relação valina/isoleucina de 0,83% e isoleucina/lisina 0,71% e T9 - ração com relação valina/isoleucina de 0,83% e isoleucina/lisina 0,75%. As características avaliadas foram desempenho, o ganho de peso, o consumo de ração, a conversão alimentar, o rendimento de carcaça e cortes comerciais. Houve interação entre os fatores para todas as características avaliadas, exceto para peso corporal aos 28 dias. Os melhores resultados obtidos nas características avaliadas foram para as aves alimentadas com (0,83% de valina e 0,75% de isoleucina), exceto para peso corporal e ganho de peso aos 42 dias, em que os melhores resultados foram obtidos pelas aves que receberam (0,83% de valina e 0,75% de isoleucina) / The objective of this study was to evaluate the performance, carcass yield and commercial cuts fed pelleted diets containing different ratios of valine / isoleucine during the growing and final (22-42 days) phase of these animals. I was used 630 one day old male cobb 500 broiler chicks during 1-22 days of age, the birds were fed a common basal diet at 22 days the birds were weighed and distributed in a completely randomized design with factorial 3x3 (nine combinations of levels of valine and isoleucine). Broilers were submitted to the following experimental treatments: T1 - ration with respect valine / isoleucine and lysine 0.75% / 0.67% lysine; T2 - ration with respect valine / isoleucine and lysine 0.75% / 0.71% lysine; T3 - ration with respect valine / lysine and isoleucine 0.75% / 0.75% lysine; T4 - ration with respect valine / lysine and isoleucine 0.79% / 0.67% lysine; T5 - tion with respect valine / isoleucine isoleucine and 0.79% / 0.71% lysine; T6 - tion with respect valine / isoleucine isoleucine and 0.79% / 0.75% lysine; T7 - tion with respect valine / isoleucine isoleucine and 0.83% / 0.67% lysine; T8 - tion with respect valine / isoleucine isoleucine and 0.83% / 0.71% lysine and T9 - tion with respect valine / isoleucine isoleucine and 0.83% / 0.75% lysine. The characteristics evaluated were weight gain, feed intake, feed conversion and carcass yield and animal commercial cuts. There was a significant interaction between the factors for all characteristics evaluated, except for weight at 28 days. The best results in characteristics were evaluated for birds receiving (0.83% of valine and isoleucine 0.75%), except for body weight and weight gain at 42 days, in which the best results were obtained the animals receiving (0.83% and 0.75% of valine for isoleucine)

This study was conducted to investigate the causes and the effects of breed, gender and season on carcass condemnations post-mortem in a large South African abattoir. Condemnation of carcasses as a results of animal diseases and conditions has been identified as a problem in the South African beef industry, but the causes and extent of carcass condemnations have not been studied in detail. The importance of cattle management during transportation and pre-slaughter is generally appreciated, but a better understanding of the influence of breed, gender and season on the prevalence of carcass condemnations can help to improve slaughter management at large abattoirs. Diseases and conditions evaluated during this study were parafilaria, bruising, soiling, fever, peritonitis and pleuritis, abscesses, measles, oedema and intramuscular haemorrhage. Breeds of cattle slaughtered were Friesland, Bonsmara, Brahman, Angus, Afrikander, Hereford and Nguni cattle, grouped as males and females, and the seasonal effects investigated were confined to Autumn, Winter and Summer combined with Spring as it was not easy to distiquish between the two. Data was collected in a Grade A abattoir in South Africa in 2010. The experimental design involved 42 combinations based on their effects and interactions namely 7 breeds x 2 genders x 3 seasons. The model used in this procedure was based on the presence of conditions = (Intercept) x i x j x k where i~breed, j~gender and k~season. The binary response variable was the presence (value = 1) or absence (value = 2) of the respective condition. Overall, the significant order and extent of causes of bovine carcass condemnations evaluated in this particular abattoir during the period of study were peritonitis and pleuritis at 2.49%, soiling 2.33%, bruising 2.10%, parafilaria 0.54%, while other conditions had a negligible effect. Almost half of these carcass condemnations were due to soiling and bruising, which can be addressed by implementing better abattoir management and better management during transportation. Peritonitis and pleuritis were prevalent to a greater degree in Autumn, Soiling in Summer, bruising in winter and parafilaria more prevalent in Summer as well. Bonsmara bulls were more affected by peritonitis and pleuritis, soiling, bruising and parafilari compared to other breeds.. Overall breed, gender and season influenced carcass condemnations in large South African abattoir It is suggested that proper dehorning should be done at an early stage, especially in bulls of breeds like Bonsmara, Nguni, Friesland and Hereford, which predispose cattle to bruising which increases the number of carcass condemnations. Steps should be taken (i.e. proper handling techniques should be applied) to avoid injuries which may lead to internal bleeding, and eventually bruises (most probably due to fighting during transportation or in lairage), that can be avoided by using improved and upgraded facilities which include enough space per animal. In case of soiling, well-trained slaughter personnel, cattle handlers and cleaners should be hired to prevent bile and soil contamination during evisceration and to avoid mud or manure contamination durinmg lairage. It is recommended that employees be trained to help reduce the high rate of carcass condemnations. Breeds like Bonsmara and Brahman were more susceptible to peritonitis, pleuritis and parafilaria, so treatrment programmes are advisable for these breeds, especially those from regions where these conditions or diseases are more prevalent. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted

O experimento foi realizado com o objetivo de avaliar o efeito de diferentes regimes de alimentação e de diferentes aditivos na dieta de suínos na fase de terminação. Foram utilizados 144 animais, da linhagem DB os quais foram pesados e distribuídos em delineamento em blocos casualizados, em esquema fatorial 2 x 4 (2 regimes de alimentação: a vontade e restrito; 4 formas de suplementação de aditivos na dieta: sem adição, cromo, ractopamina, cromo + ractopamina), totalizando 8 tratamentos com 6 repetições (3 repetições de machos e 3 repetições de fêmeas) e 3 animais cada, no período de 42 dias. Antes do início do experimento, foi avaliado o consumo médio dos animais para o fornecimento das dietas experimentais, o qual era corrigido semanalmente. Foi realizada uma restrição quantitativa da dieta em 15% em relação ao consumo dos animais alimentados à vontade, sendo que a restrição foi aplicada desde o primeiro dia do experimento e o fornecimento das dietas contendo o cromo e a ractopamina, a partir do 15º dia do experimento, ou seja, nos últimos 28 dias. Entretanto, os níveis nutricionais foram acrescidos em 15% para garantir o consumo da mesma quantidade de nutrientes da dieta. No final do experimento, um animal por repetição foi abatido para determinar a qualidade da carcaça dos animais. Foram avaliados dados de desempenho (ganho de peso, consumo médio e conversão alimentar) e de rendimento de carcaça (espessura de toucinho; espessura de músculo; porcentagem de carne magra). Os tratamentos não apresentaram efeito significativo para o desempenho dos animais sobre o consumo médio diário e o ganho médio de peso. Não houve diferença significativa para as características de carcaça. Os animais com restrição alimentar apresentaram diferença significativa (P&lt;0,001) na conversão alimentar quando comparada com a alimentação à vontade. O uso do cromo e da ractopamina de forma isolada ou em conjunto melhoraram a conversão alimentar em comparação aos animais que receberam a ração controle. / The experiment was carried out with the objective of evaluating the effect of different feeding regimes and different additives in the diet of pigs in the finishing phase. A total of 144 animals of the DB lineage were used, which were weighed and distributed in a randomized block design, in a 2 x 4 factorial scheme (2 feeding regimes: will and restricted, 4 supplementation forms in the diet: Chrome, ractopamine, chromium + ractopamine), totaling 8 treatments with 6 replicates (3 replicates of males and 3 replicates of females) and 3 animals each, in the period of 42 days. Before the beginning of the experiment, the average consumption of the animals for the experimental diet was evaluated, which was corrected weekly. A quantitative restriction of the diet was performed in 15% in relation to the consumption of the animals fed at will. The restriction was applied from the first day of the experiment and the diets containing chromium and ractopamine were applied from the 15th day of the experiment. Experiment, that is, in the last 28 days. However, nutritional levels were increased by 15% to ensure consumption of the same amount of nutrients from the diet. At the end of the experiment, one animal per replicate was slaughtered to determine the quality of the carcass of the animals. Performance data (weight gain, mean intake and feed conversion) and carcass yield (fat thickness, muscle thickness, lean meat percentage) were evaluated. The treatments had no significant effect on the performance of the animals on average daily consumption and average weight gain. There was no significant difference in carcass characteristics. Feed restriction animals showed a significant difference (P &lt;0.001) in feed conversion when compared to feed at will. The use of chromium and ractopamine alone or in combination improved feed conversion compared to animals receiving the control ration.

Orientador: Mário De Beni Arrigoni / Resumo: O objetivo do presente estudo foi avaliar a eficiência da suplementação de 25-hidroxicolecalciferol no desempenho produtivo, características de carcaça, qualidade da carne e na expressão de genes relacionados ao anabolismo e ao catabolismo do músculo esquelético de bovinos de categoria Nelore confinados. Cento e vinte machos, com peso inicial médio de 370± 20 kg provindos de pastagem contínua, foram divididos em três tratamentos de acordo com a quantidade suplementada ou não a dieta durante o período experimental: T1 - tratamento controle sem inclusão de 25-hidroxicolecalciferol; T2 - dieta + 1mg/cab/dia de 25-hidroxicolecalciferol; T3 - dieta + 3mg/cab/dia de 25-hidroxicolecalciferol, delineados em blocos casualizados (40 animais por tratamento, 5 animais por baia e 8 baias por tratamento, sendo as baias as unidades experimentais). A duração do experimento foi de 96 dias, sendo 15 dias de adaptação, divididos em dois períodos (7 e 8 dias) de dietas com níveis crescentes de concentrado (76% e 81%), respectivamente; 28 dias de crescimento e a partir desse período foram fornecidas as dietas de terminação durante 53 dias com 91% de concentrado. Os dados obtidos foram submetidos à análise de variância utilizando-se o procedimento PROC MIXED do software SAS (2003) e o teste de Tukey para comparação entre as médias, considerando significativos valores de p≤0,05. No período total do confinamento, a suplementação com 1 mg aumentou o rendimento de carcaça dos animais e os resultados d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of the present study was to evaluate the efficiency of 25-hydroxycholecalciferol supplementation in productive performance, carcass characteristics, meat quality and expression of genes related to anabolism and catabolism of skeletal muscle in Nellore cattle. One hundred and twenty male from continuous pasture, with an average initial weight of 370 kg± 20 kg, divided into three treatments: T1: control treatment without the inclusion of 25-hydroxycholecalciferol, T2: diet + inclusion of 1 mg / cab / day of 25-hydroxycholecalciferol and T3: diet + inclusion of 3 mg / cab / day of 25-hydroxycholecalciferol, outlined in randomized blocks (40 animals per treatment, 5 animals per pen and 8 pens per treatment, the pens being the experimental units). The duration of the experiment was 96 days, with 15 days of adaptation, divided into two periods (7 and 8 days) of diets with increasing levels of concentrate (76% and 81%), respectively; 28 days of growth and after that period the finish diets were provided for 53 days with 91% concentrate. The selected data will be used in the analysis of variance using the PROC MIXED procedure of SAS software (2003) and Tukey test for comparison between media, considering P values ≤ 0.05. In the total feedlot period, supplementation with 1 mg increase carcass yield and meat pH results showed a linear increase between treatments. In addition, for the variables of blood 25 (OH) D3, iCa and muscle Ca the results were higher for the treatmen... (Complete abstract click electronic access below) / Mestre

The objective was to determine how the interaction of implant strategies with the galanin receptor 2 genotype would influence feeding behavior, production efficiencies, carcass characteristics, and meat quality in finishing steers. Angus steers were selected based on GALR2-c.-199T>G genotype (n = 36 TT, 38 TG, and 19 GG). Calves were blocked by body weight and fed a standard feedlot ration, blood and BW were collected every 28 d. Steers were randomly assigned to an implant strategy of Revalor-S (1×) or Revalor-S (2×). Intake and feeding behavior data were individually recorded. There was an effect of genotype on DMI but not feed efficiency. Treatment interactions were observed for several meat quality attributes but not carcass characteristics. Altering implant strategy does not appear to interact with the GALR2-c.-199T>G genotype to alter production or carcass characteristics.

Salmonella has been studied and researched for more than a hundred years and yet it remains a problem for human and animal health. The goal of this dissertation was to apply the systems thinking approach to Salmonella contamination and develop a System Dynamics (SD) simulation model for Salmonella contamination in the chill tank of a poultry processing plant. But first the appropriate carcass rinse sampling method that would not impact on the resulting Salmonella contamination status of the broiler carcass was studied. Kappa agreement analysis was used to evaluate three sampling methods. The adjacent rinse method was found to be the best method. In the absence of actual data, literature data was used to develop a literature-based SD simulation model of Salmonella contamination of broiler carcasses in the chill tank. The literature-based SD model is the first application of system dynamics simulation modeling in the poultry-processing field. The model was able to show and simulate the dynamic and non-linear interrelationships between parameters, namely pH, chlorine (Cl) level, water flow and turbidity. Actual data collection was done using a specially designed apparatus that recorded the time, temperature, pH, chlorine, water flow and turbidity in the chill tank as carcass rinse samples were collected. Linear regression analysis was used to identify the statistically significant models for relationships between the parameters in the chill tank. Finally, the data was analyzed using logistic regression to determine the association between the parameters in the chill tank and the occurrence of Salmonellaa in carcasses exiting the chill tank. These results were used to develop a data-based SD model. The data-based model was then validated using the validity tests proposed by various authors for SD simulation models and found to be a valid model. The developed model offers a fresh perspective to the problem of Salmonella contamination- to view it as a system of factors that are interrelated and have a feedback mechanism, rather than the traditional concept of linear causation. The developed model is a powerful cost efficient tool for testing interventions for reducing Salmonella contamination in the poultry processing plant.

No description available.