Epsilon Open Archive

Abstract

The aim of this thesis was to investigate culling and mortality among Swedish crossbred sows. Data collection was prospective (2002–2004) from 21 piglet producing herds in south-central Sweden. Average annual removal rate was 49.5%. Of 14 234 removed sows, 85.2% were slaughtered, 10.5% euthanized on farm and 4.3% found dead. Most sows were removed in low parities and soon after weaning. The most common removal reasons were reproductive disorders (26.9%), old age (18.9%) and udder problems (18.1%). In addition, 96 females euthanized or found dead in one herd during 2006 were post mortem examined. Most sows were euthanized due to lameness and had arthritis as primary finding. Removal hazard was estimated using survival analysis. The factor with highest impact on sow removal was days after farrowing, followed by parity and herd×year combination. Removal hazard was highest shortly after weaning and lowest in medium parity numbers. Moreover old age at first farrowing, small litters and long intervals between weaning and next farrowing resulted in high removal hazard. Genetic parameters were estimated on genetic material supplied by the breeding organisation Quality Genetics. Heritability for sow longevity was estimated from 0.03 to 0.12 with survival analysis and linear model analysis. Correlations between estimated breeding values for longevity traits and traits included in the running Swedish breeding evaluation were estimated. Sow longevity was significantly correlated with low age at first farrowing, high litter weight at three weeks, low growth rate (birth to 100 kg) and inferior conformation (measured at station). Genetic improvement of sow longevity would be possible by including stayability from first to second litter in the breeding evaluation.