Effect of breed and body weight on thermoregulatory abilities of European (Piétrain×(Landrace×Large White)) and Chinese (Meishan) piglets at birth

Abstract

The effects of breed and body weight (BW) on thermoregulatory abilities were studied on 2–4-h-old Meishan (MS) and European (Piétrain×(Landrace×Large White)) piglets, with BW ranging between 800 and 1800 g. MS piglets ( n=17 from nine sows) exhibited similar thermogenic capacities, i.e. summit metabolic rates (SMR), than European piglets ( n=19 from 10 sows) in the cold, but BW had breed-specific effects on thermogenic capacities. First, our results confirm that, with the exception of light European piglets, SMR is proportional to BW −1 in 2-h-old animals. Second, MS piglets with BW ranging between 800 and 1300 g have similar ability to increase thermogenesis and to reduce thermolysis in the cold. On the contrary, BW has major effects on maximal thermoregulatory abilities of European piglets, with a linear relation between BW and reduction of heat loss in the cold, and a progressive impairment of thermogenic capacities below a calculated BW of 1125 g. Therefore, European piglets weighing less than 1125 g are particularly at risk in a cold environment, although they cannot be classified as runt animals. Eight additional piglets (four MS and four LW) of average BW within breeds were used to uncover the effect of breed on uncoupling protein (UCP2, UCP3) tissue expression. Expression of UCP2 does not differ but an overexpression of UCP3 is observed in adipose tissue (AT) and skeletal muscle of MS piglets, in good agreement with their higher minimal metabolic rate (MMR).