Residues in the fat of ewes grazing on soil contaminated with halogenated hydrocarbons.

Three halogenated hydrocarbon compounds were applied to the surface of each of two .57 ha bluegrass plots in October. Each plot was stocked with 10 mature ewes 6 mo after application. Supplemental feed was not offered. Five ewes remained on the plots for 180 d, whereas the other five were removed and replaced at 60-d intervals. Average soil residues for the period of grazing were 13.3, 3.8, 29.3 and 32.8 mg/m2 HCB (hexachlorobenzene), DDE [1,1-dichloro-2,2-bi(p-chlorophenyl)ethylene], DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane] and PBB (polybrominated biphenyls), respectively, for plot 1 and 16.5 and 48.0 mg/m2 DDE and PBB, respectively, for plot 2. Average concentrations of residue in body fat of the five ewes grazing for 180 d were .37, .30 and .30 micrograms/g HCB, DDE and PBB, respectively, for plot 1 and 2.41 and .79 micrograms/g DDE and PBB, respectively, for plot 2. Average residue concentrations in ewes that grazed 60-d subperiods were nearly as great, which indicated that steady state residue levels were reached in less than 180 d. A second trial and was conducted 3 yr later after plowing and reseeding the plots, but only PBB was measured. Polybrominated biphenyl was distributed throughout the top 16 cm of soil but the quantity present had not changed appreciably from the first trial. After seven ewes/plot grazed 136 d, residues were detected in only one of the seven on plot 1, but were detected in all seven on plot 2 with an average concentration of only .032 micrograms/g. It is concluded that concentration of residue in body fat of ewes depended on the concentration of chemical at the soil surface and the amount of soil ingested.

Soil ingestion by dairy cattle.

Sets of 5 to 10 random fecal samples were obtained from animals of various management groups of nine dairy herds. Titanium content of feces and soils to which the animals had access was determined by x-ray fluorescence spectroscopy. Titanium of feces was the indicator of soil ingestion, which was calculated for 60% digestibility of the total ration dry matter. Mean soil ingestion +/- standard error as a percent of dry matter intake by groups of lactating cows ranged from .14 +/- .02 to .53 +/- .05 for those confined to concrete, .35 +/- .06 to .64 +/- .18 for those housed in freestall barns with soil bedding, and .60 +/- .07 to .96 +/- .22 for those with access to unpaved lots with no vegetation. Mean soil ingestion as a percent of dry matter intake by groups of yearling heifers and dry cows ranged from .52 +/- .11 to .81 +/- .19 for those confined to concrete, .25 +/- .04 to 2.41 +/- .26 for those with access to unpaved lots with no vegetation, 1.56 +/- .21 to 3.77 +/- 1.50 for those with access to unpaved lots with sparse vegetation, and 1.38 +/- .33 to 2.43 +/- .50 for those on pasture but receiving supplemental feed. Sensitivity of the method depended on the titanium content of the soils which was four to five times greater in clay than in sandy soils. Over all observations, the percent soil of feces was related to the percent ash of feces with the orthogonal linear regression equation, Soil = .69 Ash--5.1 (squared correlations, .62).

Distribution and kinetics of PBB residues in cattle.

Cows fed a constant amount of polybrominated biphenyl (PBB) reached a steady-state concentration in milk fat within 30 days. This concentration was approximately four times the concentration in the total diet. When feeding of PBB was stopped, the concentration in milk was adequately described as a sum of two first-order elimination rates. Biological half-life in environmentally contaminated cows, studied for 6 months about a year after contamination, was 60 days. The stage of lactation affected the rate of elimination, and in some concentrations increased shortly after calving. Residues were distributed in body tissues proportionally to concentration of fat in the tissues. Liver and brain were exceptions. Concentration in liver fat was generally higher than other tissues and possibly related to the treatment of some cows with phenobarbital. Residues in brain fat were significantly lower than all other tissues. The ratio of the concentrations in milk fat to concentration of residues in the blood of calves and fat of fetal tissues to the concentration in the corresponding tissue in the dams was 0.36:1. It was estimated that people consuming milk from the highly contaminated Michigan cows could have received PBB doses as great as 10 g from this source alone.

Hexachlorobenzene retention and excretion by dairy cows.

Two groups of three cows each were fed either 5 or 25 mg of hexachlorobenzene per day for 60 days. A reference compound, DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), was fed to the cows at the same rate. Residues were determined in milk at 5-day intervals during the 60-day dosing period and for 60 days after dosing was stopped. The concentration of hexachlorobenzene in milk fat increased more slowly than did that of the reference compound during feeding. The ratio of the two was 1:2 at 10 days, but approached 1:1 after 40 days of feeding. The average concentrations in milk fat for the 40th to 60th days of feeding were 9.0 and 10.4 ppm with the 25-mg/day intake and 2.1 ppm for each compound with the 5-mg/day intake. Corresponding values in subcutaneous body fat were 8.8, 8.0, 1.9, and 1.4 ppm at 60 days. Milk fat concentrations of hexachlorobenzene declined 32% and those of the reference 51% within 15 days after feeding stopped. Thereafter, the decline was slower but similar for both compounds. Biological half-lives ranged from 29 to 64 days for individual cows. The milk fat:body fat concentration ratio was .87:1 for hexachlorobenzene and .71:1 for the reference during the 60 days when cows were not fed the compounds.

Excretion of polybrominated biphenyls into the milk of cows.

Four cows each were fed 10 mg/day polybrominated biphenyl for 60 days. Concentration in milk fat reached a steady state at 3.07 ppm within 30 days. When feeding polybrominated biphenyl was stopped, the concentration declined 71% in the first 15 days. The decline was slower thereafter, with a half-life of 58 days. Effects on health and production of the cows were not adverse for as long as 1 yr after the compound was fed.