[Mobilization of body stores in the lactating primiparous sow]

To determine the nature and the amount of the tissues involved in weight loss during lactation, an experiment was carried out on 9 series of 3 littermate Large-White gilts divided into three groups. The animals were similarly raised until first farrowing. The control gilts were slaughtered at farrowing, while those in the other two groups (group H and group B) received diets differing only in energetic level (14.2 and 10.3 Mcal ME/day, respectively). The gilts were slaughtered after 22 days of lactation. Half-carcasses were cut and dissected. Muscle weight decreased similarly in the two lactating groups (-9.5 and -11.3 kg in groups H and B, respectively), but fat loss was higher in the energy-restricted animals (-6.7 vs -1.7 kg). These results were confirmed by changes in adipose cell size, blood urea and plasma free fatty acids between farrowing and weaning.