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Locomotion disorders have been identified as a significant production disease for growing and finishing pigs, and a sign of reduced animal welfare (EU PROHEALTH project). Amongst them, lameness is a complex problem including animal-based and resources-based causes. Osteochondrosis (OC) is a very frequent disease in pigs, affecting cartilage. The study assessed the occurrence of lameness and OC in two divergent lines of Large-White selected according to a feed efficiency trait (HRFI, LRFI; high or low residual feed intake), submitted to constraints on the physical activity. Two experimental groups of 80 pigs (40 LRFI and 40 HRFI, ratio 1:1 of females and castrated males) were housed on partly slatted flooring in a room equipped withan electronic weighing device allowing pig access to electronic self-feeders, crossing a sorter. Pigs were equipped with ear tags for their individual electronic identification at the sorter and automatic feeders. The identification determined the side of the room to which the animal was directed after the sorter exit, and thus defined the distance to come back to the sorter (short: spontaneous activity, long: increased activity). Three times, at the beginning (wk3), middle (wk7) and end (wk13) of the growing-fattening period, video recordings were made during the 12 h daylight for screening the posture (standing, sitting, lying). Lameness was assessed weekly using a visual gait scoring (lameness score, 0: no, 1: lame). At slaughter, (weight of 100kg, between 21 and 22 wks of age), post-mortem quantification of OC lesions was performed on surfaces of both proximal and distal condyles of the humerus and femur (score 0 no lesion; score 5 severe lesion with loose fragment of cartilage). According to the variables, data were analyzed using a χ2 test or variance analysis with the main factors line, physical activity, sex, replicate and their interactions. The LRFI line showed fewer pigs standing during the daylight period at the three recording times (22.5±0.6 vs 28.3±0.6% of standing pigs during a 30 min interval, P

Locomotory disorders and more specifically lameness have been identified as one of thesignificant production diseases for growing and finishing pigs and sows. Lameness is acomplex problem with multifactorial causes. Among these causes, osteochondrosis has avery high prevalence in all common pig breeds. Osteochondrosis is a local failure of epiphysisendochondral ossification that can be responsible, in its more severe form, of cracks at the levelof joint cartilage. However, the proportion of lameness that can be linked to osteochondrosisis difficult to evaluate and still unknown. The PROHEALTH project aims at evaluating theinfluence of genetic selection on productive traits on the prevalence of leg disorders and todevelop a methodology to assess lameness and osteochondrosis. For this purpose, 3 experimentsaimed at measuring the prevalence of osteochondrosis in several populations of pigs. The testedpig populations included two divergent lines of Large-White selected for a feed efficiency trait(high or low residual feed intake) and two lines of Landrace selected for either their high fertilityperformance or their high growth performance. The Large-White populations were submittedto different constraints on the physical activity. These experiments also allowed identifying sexeffects as females, entire and castrated males were studied within similar populations. All theseexperiments showed that osteochondrosis is very common in femur and humerus joints. InLandrace pigs, only 11% of the examined joints (539) were discovered as normal and 89% ofjoints had some signs of osteochondrosis. Within each breed, Large-White or Landrace, theosteochondrosis prevalence was not different between the compared lines but an effect the sexwas observed. Boars were more susceptible for osteochondrosis than gilts. A question arisesabout the relevance of blood bio-markers of cartilage synthesis or turnover for easy and earlydiagnosis of osteochondrosis. The correlation between the serum concentrations of thesebio-markers and the osteochondrosis scores remained low even if the reproducibility of theseanalyses during the animals’ life were quite high.