Effects of clinical lameness and tail biting lesions on voluntary feed intake in growing pigs

Abstract

A decreased feed intake is considered one of the first signs of disease in farm animals. Feeding-related individual data collected by electronic feeding systems may thus be useful in detecting illness at an early stage. The aim of this study was to determine changes in individual-level voluntary feed intake in growing pigs before and after a bout of sickness modelled by clinical lameness or an acute tail (biting) lesion, which together count for a significant part of overall health problems in intensive pig production. The data consisted of individual records of health and day-level feed intake in fattening pigs between about 40 and 120kg obtained from the Finnish progeny test farm. Feed was available ad libitum from automatic single-space feeders. Two time periods in relation to diagnosis (day 0), day −50 to 0 (pre-) and day 0 to +50 (post-), were modelled separately for both diagnoses using hierarchical linear models with random and repeated effects. All healthy animals in the affected animals' pens were used as controls. The number of pigs in the different analyses were 243/551 (cases/controls, pre-tail lesion), 205/693 (post-tail lesion), 116/588 (pre-lameness) and 165/892 (post-lameness).Feed intake in the study animals was affected by sex, weight at arrival to the farm, health status (lame or tail bitten case vs healthy control), eventual recovery (culled or dead vs recovering to slaughter condition), the day relative to diagnosis and approximate age (the day on the farm), with the four latter factors involved in multiple interactions. Feed intake started decreasing already 2–3 weeks pre-diagnosis in future lame or tail bitten animals, suggesting a common predisposing factor such as reactive coping. Feed intake decreased substantially (13–99%) from control levels in sick animals, with the level dependant on diagnosis, degree of eventual recovery and age. Lame animals ingested two to three times less than tail bitten ones at diagnosis. Within both diagnoses, culled-to-be animals ingested roughly half the relative amount of those recovering to slaughter condition, suggesting that relative feed intake at diagnosis may predict the outcome of disease. Younger animals were generally more severely affected than older ones. Anorexia was prolonged up to about 30 days in culled-to-be lame animals in contrast to all other groups modeled, which started recovery immediately upon diagnosis and initiated treatment. The observed changes and differences in feed intake may indicate differences in animal welfare.