Poids et métabolisme des réserves lipidiques au cours de la croissance du chevreau

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Adipose tissue growth was studied in two experiments. In the first one, 36 Alpine male kids fed with milk replacer only were slaughtered at 8, 14 or 20 kg (groups A, B and C, respectively). Perirenal adipose tissue developed earlier than omental adipose tissue, but from about 30 days of age, the latter was heavier (allometric coefficients: 2.18 and 1.36 for omental and perirenal adipose tissues, respectively). Even in group C animals, subcutaneous adipose tissue was scarce. When expressed in grams of wet tissue, the lipoprotein lipase (LPL) activity of omental adipose tissue decreased with age. This decline was more marked between groups B and C than between groups A and B (37 and 14%, respectively). Total LPL activity of omental tissue was 3-fold higher in group B than in group A and 3.7-fold higher in group C than in group A. This activity apparently had no relation with the amount of milk intake, daily mean weight gain or omental adipose tissue weight. In the second experiment, 18 male kids were slaughtered unweaned at 6 weeks or 2 or 14 days after weaning (groups A, B and C, respectively). After weaning, the weight of all adipose tissues decreased. Perirenal adipose tissue weight diminished earlier and more intensively than in the other adipose tissues (80% weight drop in 14 days). The weight loss of omental, pericardiac and mesenteric adipose tissue was 65, 49 and 15%, respectively. As with other lipogenic enzymes, the activity of LPL was highest in omental adipose tissue. In perirenal, pericardiac and mesenteric tissues LPL activity was 30, 45 and 60% less than omental activity. In sternal adipose tissue, LPL activity was very low. Acetyl CoA carboxylase (ACX) was active in the internal tissues of unweaned kids, but at a low level, i.e. about one-twentieth of that of LPL. Glucose-6-phosphate dehydrogenase (G6PDH) had a higher activity than NADP-malate dehydrogenase (EM). Soon after weaning, all of these enzyme activities dropped sharply. Two days after weaning, LPL activity declined by about 90% in all tissues, but 14 days after weaning it rose again, especially in perirenal adipose tissue. However, it reached a lower value than in unweaned kids. On the contrary, 14 days after weaning, group C ACX activity returned to a lower value than that of group B.