Uptake and excretion of organochlorine compounds in neonatal calves

Intestinal absorption mechanisms of young calves change rapidly during the first 24 h postpartum and subsequently effect the absorption efficiencies o f a wide range of compounds. This study was conducted to determine absorpti on efficiencies of (p,p'-dichlorodiphenyl)dichloroethylene (DDE), 2,2',4,4' ,5,5'-hexachlorobiphenyl (PCB-153), and 1,2,3,4,6,7,8,9-octachlorodibenzo-p -dioxin (OCDD) when administered in colostrum to neonatal calves. Four male Holstein calves were given a single oral dose containing 100 mg each of DD E, PCB-153, and OCDD either 1 h (n = 2) or 65 h (n = 2) postpartum to deter mine whether time of exposure influenced the rate or extent of absorption. Another male calf received 100 mg each of DDE and OCDD 1 h postpartum One g ram of chromic oxide (Cr2O3) was administered as a digestion marker to dose d calves. Two male calves, receiving only colostrum, served as controls. Se rum IgG concentrations indicated that the l-h calves absorbed 20 to 37% of the ingested IgG and 65-h calves < 2%; therefore, the gut absorption mechan isms had changed by 65 h. Plasma DDE, PCB-153, and OCDD profiles did not di ffer based on time of exposure, suggesting that their mechanism of absorpti on was not influenced by the changing gut. Trapezoidal area under the curve to the last time point values indicated that, during the trial, relative p lasma organochlorine concentrations amounted to PCB-153 > DDE > OCDD. Tissu e concentrations were similar across treatment groups, with DDE and PCB-153 residues concentrating in adipose tissue and OCDD in the liver. Absorption efficiencies, calculated from fecal recoveries, were >97%, >74%, and >72% for DDE, PCB-153, and OCDD, respectively. These doses of DDE, PCB-153, and OCDD (2.5 +/- 0.1 mg/kg) did not produce signs of toxicosis based on detail ed clinical observations, serum clinical chemistry, and gross and histologi cal observations at necropsy. The results of this study indicate that DDE, PCB-153, and OCDD were absorbed and distributed similarly in calves exposed 1 or 65 h postpartum and did not induce toxicosis when administered in com bination at these concentrations.