Impact of poor hygiene on health and performance of pigs divergently selected for feed efficiency

Production diseases impair production efficiency and animal welfare. Pigs with improvedproductive traits are suspected to be more at risk to develop diseases because of a lowercapacity to allocate their nutritional resources for health. The aim of this study was to assesshealth and performance of two pig lines divergently selected for feed efficiency and housed ingood or poor hygiene environment. Poor hygiene is known to induce inflammatory disordersand reduce growth performance. Large-White male and female pigs (n=160) from 80 to 160days of age were included in a 2×2 factorial design comparing 2 lines divergently selected forResidual Feed Intake (low RFI=more efficient and high RFI=less efficient) and housed in 2hygienic conditions (clean (C) vs dirty (D), n=40/group). The experiment was divided in twosuccessive periods: during the challenging period, from Week 0 (W0) to W6, pigs were eitherhoused in C or D conditions; blood was collected at W0, W3 and W6. During the recoveryperiod, from W6 to W12, all pigs were housed in clean conditions. Half of the pigs in eachgroup were euthanized at W6 and the remaining pigs were euthanized at W12 to collect tissueand evaluate body composition. Throughout the experiment, pigs were individually pennedand had free access to a standard growing diet. Body weight and signs of clinical diseases(cough, diarrhea, lameness) were weekly recorded. Blood was collected to assess indicatorsof inflammation (haptoglobin, blood formula) and metabolite concentrations. Prevalenceof pleurisy and pneumonia at slaughter was greater for D than C pigs. Average daily gain(ADG) from W0 to W6 was lower in D than C pigs, and this reduction was greater for thehigh RFI line (-247 g/d) than for low RFI line (-107 g/d). At W3, D pigs exhibited greaterblood haptoglobin and neutrophil contents than C pigs, showing that poor hygiene conditioninduced an inflammatory response. Disparities were observed between the two lines withhigher haptoglobin in high RFI pigs and higher amount of neutrophils in low RFI pigs. FromW6 to W12, ADG and health blood biomarkers did not differ between D and C pigs, suggestingthat pigs had recovered. In conclusion, low RFI pigs were less affected by the environmentalchallenge, which disagrees with our initial hypothesis. Data to be obtained on metaboliteconcentrations and expression levels of genes related to immunity will allow determining ifthe line differences in the ability to cope with this sanitary challenge were related to differencesin resource allocation, immune capacities or growth precocity