Variabilité de la capacité d'adaptation des porcelets au sevrage en agriculture biologique. Variability of piglets' adaptability at weaning in an organic farming system

In organic farming, piglets at weaning are often heterogeneous in age and weight, and weaning remains a critical period, despite piglets are weaned later than in the conventional system. The heterogeneity is reinforced by a poorly adapted solid diet after weaning. The aim of this pilot study was to establish profiles of piglets with different adaptive strategies at weaning based on body weight, feeding behaviour, and blood indicators. Fifty piglets were born from five sows (Landrace x Duroc) and a boar (Large White x Pietrain). On day 10 (d10), solid feed was provided ad libitum. After weaning (d42), piglets had still access to the solid feed and had access to Wrapped alfalfa roughage, both ad libitum. Piglets were allotted in five pens of 10 weaned piglets. Piglets were weighed before (d1-10-21-28) and every week after weaning (d42) up to d70. Blood was collected on d42 and d48. Behavioural observations were video-recorded the day after weaning (d43). Despite the late age at weaning, greater concentrations in haptoglobin and dROM were observed on d48 (P < 0.05). Three classes of piglets were identified according to their body weight on d42: Small [5.9-12.4 kg], Medium [12.4-13.9 kg] and Large [14.0-18.4 kg] piglets. The Small piglets spent on average more time (P = 0.006) in the feeding area and had higher (P < 0.05) haptoglobin plasma concentration compared to the Large piglets. Average weight still differed (P < 0.001) between all three categories on d70 showing that the Small piglets did not compensate their low body weight to catch up the larger piglets. Further analyses are currently ongoing for a better characterization of the adaptive profiles.