Studies on metabolism of broilers by using 14C-labelled DL-methionine and DL-methionine hydroxy analogue Ca-salt

The metabolization of DL-methionine and a hydroxy analogue form, DL-MHA-Ca, was studied by means of 14C-labelled substances. For this purpose 60 male day-old chicks were administered 1-14C-labelled substances DL-methionine and DL-MHA-Ca into the birds' crop. In 20 birds the 14CO2 activity excretion with the expired air was measured for a period of 24 hours post administration by means of radiorespirometry. The birds were killed 24, 48 and 72 hours post administration and the 14C-activity determined in the following fractions: excrements, gastrointestinal contents, digestive tract, blood, kidney, liver and gallbladder, lung, heart, spleen, leg and breast muscles and the residual fraction. Over the experimental period as a whole 17.0% of the administered dose was recovered in the excrements of the 1-14C-DL-MHA-Ca labelled birds and 4.4% in the 1-14C-DL-methionine treated birds. The maximum 14CO2 excretion in the expired air was reached after 1.5 hours, irrespective of whether 1-14C-DL-methionine or 1-14C-DL-MHA-Ca had been administered. Within 24 hours post administration, 15.8% of 1-14C-DL-methionine were excreted as 14CO2 via the lungs, as against 11.4% following application of 1-14C-DL-MHA-Ca. While no significant differences between the groups were recorded for the 14C-incorporation of the liver, the kidneys generally contained a higher 14C-activity after the administration of 1-14C-DL-methionine than after 1-14C-DL-MHA-Ca. The relative incorporated 14C-activity was distributed in the following proportions: 25% in the leg and breast muscles, about 25% in the remaining organs and about 50% in the residual fraction. The 14C-activity found in the protein of the leg and breast muscles was separated by thin layer chromatography and recovered exclusively in methionine. The 14C-activity in the lipids of the leg and breast muscles accounted for only a very small proportion of the total incorporated 14C-activity. Irrespective of the adaptation diet, the rate of incorporation of 14C into the birds' body was found to be higher after administration of 14C-DL-methionine than after 1-14C-DL-MHA-Ca.