The period of growth from parturition to weaning is a time of rapid fat deposition in many species. In the pig, body fat increases from about 10 g/kg at birth to 150 to 200 g/kg by 21 days of age (Wood and Groves 1965; Whittemore, Aumaitre and Williams, 1978). An adequate reserve of adipose tissue may be crucial to ensure health and survival, for example during the period of low food intake frequently observed after weaning.
It is likely that the nutrient composition of milk and the hormonal signals elicited by milk consumption play an important rôle in stimulating fat deposition. We have investigated the effects of milk ingestion on release of the gastrointestinal hormones GIP (gastric inhibitory peptide) and GLP-1 (glucagon-like peptide one). In addition, we have studied the effects of these hormones on fatty acid synthesis in vitro.
Explants (0.4 to 0.6 mg) of adipose tissue were obtained from three anatomical sites of an 18-day-old pig fasted for 12 h. The explants were pre-incubated for 90 min and then incubated in the presence of hormones and [14C] acetate (0.2μCi/ml). Triacylglycerols were extracted from the explants and following saponification, fatty acids were separated and radioactivity counted.