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Title: Evaluation of pigs' welfare and meat quality in relation to housing, transport and slaughterhouse procedures
Other Titles: Evaluatie van het welzijn en vleeskwaliteit van varkens in relatie tot huisvesting, transport en slachthuisprocedures
Authors: Van de Perre, Vincent
Issue Date: 4-Nov-2011
Abstract: In Belgium, fresh pig meat is one of the most exported food products. The total export in 2010 was 702,576 tons, which is 68% of the total Belgian pig meat production and is 2 % more than the previous year. These results confirm the rising trend of the past five years. Accordingly, it is very important to deliver good quality of meat and financial losses need to be avoided. Stress and consequently impaired animal welfare might be an important cause of financial loss by affecting pigs’ behaviour and meat quality. The aim of this research is to study the effect of (1) stressors such as ventilation and environmental enrichment on pigs’ biting behaviour and (2) pre-slaughter stress on meat quality of fresh and processed meat. Tail and ear biting are severe problems in modern pig production, have a multi-factorial origin and might result in a reduction of animal welfare and productive performance. This abnormal behaviour is investigated in the first part of the study (Chapter 2 and 3). In Chapter 2, the effect of genetics and ventilation on pigs’ biting behaviour was investigated. All pigs originated from one of two Piétrain boars, originating from two different lines. Genetics and ventilation were found to have a significant impact on the biting behaviour and the appearance of wounds. More precisely, pigs descendant of a boar, which had a better conformation and higher lean tissue content than pigs originating from the other boar, were more vulnerable for inappropriate ventilation, i.e. more pigs showed biting behaviour and more wounds were seen. In Chapter 3, the effect of a sequence of toys (weekly change) versus a single toy (chain) on pigs’ biting behaviour during the complete fattening period are reported. Toy contact and biting pen mate behaviour were observed on the day of introduction of the toy and five days later. The continuous sequence of seven enrichment objects reduced biting pen mate behaviour and the number of wounds compared to the providing only a single toy. The study also confirmed that not every object was feasible as an enrichment object for growing pigs. Generally, the most toy contact was observed together with the highest biting pen mate behaviour and could be induced by the competition for popular toys. However, biting pen mate behaviour was still the highest in pens with only a chain as enrichment object. Furthermore, habituation still occurred since toy contact behaviour was lowest at observation day five or decreased when the same toys were provided for the second or third time. The ideal sequence should maintain toy contact behaviour without competition in order to avoid biting pen mate behaviour and reduced animal welfare. No effect on growth and feed conversion was seen. In consensus with Chapter 2, biting pen mate behaviour decreased over age since the activity of pigs decreased over age. PSE meat is still a common meat quality defect in Belgium and pre-slaughter stress is the determining factor being multifactorial in its nature. The effect of several pre-slaughter parameters concerning transport, unloading, lairage, pig handling, stunning and season on fresh meat quality based on pH measurements 30 min after slaughter are reported in Chapter 4. Ten pre-slaughter parameters had a significant effect on meat pH after separate introduction of the variables as a fixed effect in the model. Simultaneous analysis of these variables in the global model revealed that the pH was influenced by four main risk factors, namely the mean noise level produced during unloading, the percentage of panting pigs, the use of an electric prod and season. Meat quality in terms of the percentage of potentially PSE carcasses was better in summer than spring or autumn and could be explained by a lower observed pre-stunning stress in summer. The processing of meat with PSE or DFD characteristics has determinable effects on the quality of the end product. As a result, measurements in the slaughter line that can predict the quality of the processed meat product would be very interesting and is studied in Chapter 5. Meat quality measurements (pH, electrical conductivity, colour and/or water holding capacity) were carried out 30 min, 24 and/or 35 h after slaughter in three different muscles: M. gracilis, M. semimembranosus and M. longissimus dorsi. From these measurements, a tendency towards a higher proportion of PSE meat during summer was found compared to winter. Moreover a higher protein, a higher dry matter content, a lower water/protein ratio and a lower slicing yield were found for the cooked hams suggesting a higher PSE prevalence in the summer. These results, in combination with the results of Chapter 4, showed that pre-slaughter stress, temperature fluctuations and weather conditions might be more important factors than season concerning the occurrence of PSE meat. Temperature fluctuations and weather conditions were not measured and need to be considered in further research. Chapter 5 also showed that multiple meat quality measurements can provide more information about the meat quality but are not easy to perform on an industrial scale. From this study, it can be concluded that the ultimate pH measurements (after 24 h and 35 h) in the three examined muscles, and certainly the ultimate pH in the M. gracilis, are good measurements to predict colour 24-35 h post-mortem and the meat quality of hams after cooking.The results of this thesis showed that good rearing practices for pigs also involves appropriate ventilation and the provision of enrichment objects that can maintain novelty. If the proposed pre-slaughter stressors are taken into account, i.e. minimal pre-slaughter stress, meat quality can be improved. However, further research is needed to associate good rearing practices for pigs with their final meat quality. This can practically be true when pre-slaughter stress is very low.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Division of Livestock-Nutrition-Quality
Centre for Animal Husbandry

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