| recurrent viruses in a singapore intensive pig farming estate. | the ponggol intensive pig farming estate was conceived approximately 10 years ago to accommodate pig farms resettled from water catchment areas. initially stocking density of the estate was 1300-1500 pigs per hectare (ha) and the total pig population in the estate was 200,000. over the past 10 years the numbers of pigs have increased to 400,000 and the stocking density of the big commercial units have increased to 1500-2500 per ha. with such intensive methods of husbandry environmental problems ... | 1987 | 3446006 |