Four experiments were conducted to evaluate the effect of beta-endorphin (beta-END) on feeding, drinking and colonic temperature in rapidly growing (Rock-Cornish; RC) and slow growing (Single-Comb White Leghorn; SCWL) stocks of chickens. In the first experiment RC cockerels were injected intracerebroventricularly (ICV) with 0, 1.5, 3.0 and 6.0 micrograms of beta-END. In the second experiment RC cockerels were injected ICV with 0.5, 1.0 and 2.0 micrograms of beta-END. Experiments 3 and 4 were conducted identically to Experiment 1 and 2, respectively, except SCWL were used. Administration of beta-END at levels between 1.5 and 6.0 micrograms produced a significant curvilinear increase in feeding in both RC and SCWL chicks. In RC chicks, feeding was significantly elevated at 45 min and from 90 through 240 min postinjection, whereas in SCWL chicks feeding was increased from 90 through 300 min postinjection. Water intake was depressed in RC and SCWL from 60 through 90 min and from 30 through 60 min postinjection, respectively. Significant increases in water occurred at 180 and 300 min postinjection in SCWL. beta-END also induced a significant hyperthermia in RC and SCWL from 30 through 240 min and from 15 through 180 min postinjection, respectively. At low levels of beta-END, i.e., 0, 0.5, 1.0 and 2.0 micrograms, feeding, drinking and body temperature were significantly increased in both stocks. Feeding in RC chicks was stimulated in a linear fashion from 180 through 300 postinjection while feeding in SCWL was stimulated in a curvilinear manner from 180 through 240 min postinjection.(ABSTRACT TRUNCATED AT 250 WORDS)