Impact of poor hygiene on health and performance of pigs divergently selected for feed efficiency
Résumé
Production diseases impair production efficiency and animal welfare. Pigs with improved
productive traits are suspected to be more at risk to develop diseases because of a lower
capacity to allocate their nutritional resources for health. The aim of this study was to assess
health and performance of two pig lines divergently selected for feed efficiency and housed in
good or poor hygiene environment. Poor hygiene is known to induce inflammatory disorders
and reduce growth performance. Large-White male and female pigs (n=160) from 80 to 160
days of age were included in a 2×2 factorial design comparing 2 lines divergently selected for
Residual Feed Intake (low RFI=more efficient and high RFI=less efficient) and housed in 2
hygienic conditions (clean (C) vs dirty (D), n=40/group). The experiment was divided in two
successive periods: during the challenging period, from Week 0 (W0) to W6, pigs were either
housed in C or D conditions; blood was collected at W0, W3 and W6. During the recovery
period, from W6 to W12, all pigs were housed in clean conditions. Half of the pigs in each
group were euthanized at W6 and the remaining pigs were euthanized at W12 to collect tissue
and evaluate body composition. Throughout the experiment, pigs were individually penned
and 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 indicators
of inflammation (haptoglobin, blood formula) and metabolite concentrations. Prevalence
of 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 the
high RFI line (-247 g/d) than for low RFI line (-107 g/d). At W3, D pigs exhibited greater
blood haptoglobin and neutrophil contents than C pigs, showing that poor hygiene condition
induced an inflammatory response. Disparities were observed between the two lines with
higher haptoglobin in high RFI pigs and higher amount of neutrophils in low RFI pigs. From
W6 to W12, ADG and health blood biomarkers did not differ between D and C pigs, suggesting
that pigs had recovered. In conclusion, low RFI pigs were less affected by the environmental
challenge, which disagrees with our initial hypothesis. Data to be obtained on metabolite
concentrations and expression levels of genes related to immunity will allow determining if
the line differences in the ability to cope with this sanitary challenge were related to differences
in resource allocation, immune capacities or growth precocity.