INTRAPERITONEAL ADMINISTRATION OF TRYPTOPHAN DECREASES LIQUID DIET INTAKE IN EARLY WEANED PIGLETS

The aim of the present study was to investigate the effect of intraper itoneal tryptophan (Trp) administration on liquid diet consumption in early weaned piglets. Furthermore, the effects of two chemical forms o f the amino acid were compared. Single doses (100 mg.kg(-1)) of L-tryp tophan (480 mmol.kg(-1)) or L-tryptophan methyl ester (392 mmol.kg(-1) ) (Sigma, USA) were i. p. administered at 07.00 h to 2 groups of 5 pig lets each at the age of 3, 9, 12, 14 and 16 days. The piglets were wea ned on d 1, housed individually in cages and offered a commercial diet (Selasan) for suckling from feeding bottles between 06.00 and 22.00 h 9 times a day at 2-h intervals with an 8-h break at night. Control pi glets (n=5) were left intact. Compared with intact controls, L-Trp dec reased the relative sizes of individual meals in piglets aged 3 d only 5 h (P < 0.02) after its administration, in the 9-d-old ones 1, 3 and 5 h (P < 0.05; P < 0.01; P < 0.05, respectively), and in the 16-d-old piglets 3 h (P < 0.01) later. No significant differences between cont rol and L-Trp-treated animals occurred on days 12 and 14. L-Trp methyl ester decreased the diet consumption of piglets at all ages as follow s: in 3-, 9- and 16-d-old piglets 3 h (P < 0.05; P < 0.05; P < 0.01, r espectively) post-injection, in the 12-d-old animals 1 h (P < 0.01), 3 h (P < 0.001) and 7 h (P < 0.05), and in the 14-d-old piglets 1 h (P < 0.01) and 3 h (P < 0.01) after L-Trp methyl ester administration. In 12- and 14-d-old piglets its effect was also reflected in 24-h diet i ntake that was significantly decreased. Similar differences in diet co nsumption were found when the relative sizes of individual meals were compared to the first morning consumption, i.e. 1 h before Trp treatme nt. In conclusion, Trp did suppress food consumption in early weaned p iglets as soon as on day 3 after birth, indicating that the aminostati c component of their food intake regulation is functional at this age. At the same time it was found that this effect of L-trp methyl ester (the actual dose of which was smaller than that of L-Trp) occurs earli er, is more profound and lasts longer than that of L-Trp.