Abstract
Modern swine production coupled with expanding global movement of people and animals increases the chance of introduction and spread of pathogens in US swine populations. Although the US swine herd is free of African Swine Fever (ASF), there is ongoing transmission throughout China, parts of Europe, and the Dominican Republic; and preparation of contingency plans remains a high priority for the US swine industry. These plans must include detailed steps for depopulation of large numbers of swine in a short timeframe. Several methods are recommended by the AVMA; but one solution does not fit all situations in the U.S. pork industry. Water-based foam may provide an additional solution for an emergency depopulation event; therefore, the main goal of our project is to add to the body of knowledge on water-based foam as a potential method for swine depopulation. Specific objectives of this project were to 1) assess the effect of fill rate of water-based foam on the welfare of finishing pigs; and 2) Determine the optimal depth of water-based foam for depopulation of finishing pigs.
A subset of pigs (N = 153) from a 4000-head wean-to-finish facility were enrolled in the study and were depopulated using a modified 64.5-m3 (dimensions 12.2 × 2.36 × 2.24 m; length, width and height) rendering trailer. Foam was generated during using a Class A foam concentrate (1%), and delivered using medium expansion aspirated foam nozzles. For objective 1, 77 finisher pigs were divided into 3 treatments groups with 2 replicates each based on a pre-established fill rate (slow, medium, or fast). Pigs had subcutaneous data loggers that allowed for activity and electrocardiogram (ECG) data collection. For objective 2, 76 finisher pigs were assigned into 3 treatment groups with 2 replicates each based on a predetermined foam fill level (99 cm, 116 cm, or 132 cm) from the trailer floor. A trained welfare specialist observed and timed the entire depopulation process for both objectives.
Results from our study showed that time to cessation of movement was significantly longer in the slow foam rate treatment compared to the fast and medium foam rate treatments. Furthermore, the number of foam surface breaks were the highest for the slow fill rate treatment compared to the number seen in one of the fast fill rate replicates. The number of surface breaks was also higher for the 0.99m fill depth. No vocalizations were heard for any of the treatments. In conclusion, our trials showed that for WBF depopulation of swine in smooth-sided containers, immersing animals in foam within 90 seconds and using a fill depth of at least 1.75x times the pig head height is recommended to reduced animal stress levels while ensuring a rapid destruction.
