No abstract

Concentrations of progesterone, estrogen, and prolactin in plasma were compared among lactations induced in 29 cows by daily subcutaneous injections of .25 mg progesterone and .1 mg estradiol-17beta per kg body weight for 7 days. Superior, median, and inferior lactations were identified by ranking both weightage adjusted maximum milk yields in 7 consecutive days (average 144 +/- 9 kg) and days for milk yield to increase from 5 to 10 kg/day (15 +/- 3 days). Superior and inferior of the former averaged 189 and 101 kg, and their latter averaged 2 and 42 days. Plasma hormones were measured on day 0 before first treatment (day 1), and on days 7, 14, 17, 21, 24, 28, and 35. Superior lactations were associated with below-average progesterone and estrogen in plasma on day 0, rapid decreases in progesterone after day 7 and in estrogen after day 14, and increased prolactin after 7. In comparison, median lactations were associated with elevated progesterone and estrogen after day 17, but prolactin was similar to that of superior lactations. Inferior lactations were associated with decreased prolactin in plasma from days 21 to 35. We hypothesized that (a) first treatment should start 3 to 8 days after estrus, (b) daily doses of estradiol-17beta should be decreased with progesterone unchanged for the 7 days, and (c) estradiol-17beta alone should be continued for 7 days to improve hormonally induced lactations.

The distribution and clearance of polybrominated biphenyls were determined in two cows and a calf fed polybrominated biphenyls by boluses, by placental transport to a calf from a contaminated dam, and to another calf via milk from the contaminated dam. Feces were an important route of excretion of polybrominated biphenyls during exposure and the period when the contaminated feed was cleared from the digestive tract. Approximately 50% of single intraruminal doses of these hydrocarbons were cleared by 168 h. Free polybrominated biphenyls in urine could not be quantitated. However, 24% of carbon-14 from tetrachlorobiphenyl was recovered, suggesting that significant quantities of halogenated biphenyl may be excreted in urine. Milk was also an important excretion route with one cow excreting 23% of the polybrominated biphenyl dose in 168 days. Concentrations of polybrominated biphenyls in the fat of most tissues were similar, with higher concentrations in liver and lower in the nervous system. Gross or histopathologic lesions of tissues collected at necropsy could not be related specifically to polybrominated biphenyl toxicity.

No abstract

Sixty dairy animals were utilized in seven experiments to determine aspects of the distribution and clearance of FireMaster BP-6. Experimental protocols of various studies provided daily exposures from 0.25 to 25,000 mg, exposures for I to 202 days, and total study periods from 10 to 1100 days. Necropsy of 28 animals provided information on residue concentrations in 35 tissues, and the excretion in milk was determined in 15 animals. These studies showed that the major brominated biphenyls of this commercial mixture were absorbed from the gastrointestinal tract and appeared in the blood plasma within 4 hr. With continued exposure to the residue plasma concentrations reached a steady state by 15 days. Free PBB was not detectable in urine. During PBB feeding feces was the major route of excretion, representing approximately 50%o of the amount fed to animals not displaying signs of toxicosis. Following withdrawal of PBB, fecal concentrations declined to 1 to 2% of concentrations during dosing, yet, feces remained the major excretory route in nonlactating animals. In contrast, in post-exposure lactating animals milk fat became an important excretory route removing three-times the quantity of residue cleared in feces. Following parturition, concentrations of PBB in milk fat declined approximately twofold in 6 days. Thereafter, the residue concentration in milk fat was approximately 0.4 that in depot fats. PBB had a predilection for lipid tissues with similar concentrations in various depot fats. Concentrations of the residue were notably low in tissues of the nervous system despite the high content of lipid material. Liver contained residue concentrations that were disproportionately high when compared to the lipid content of the organ. Calves born to PBB-exposed cows had similar distribution of residues in body tissues although concentrations were less than those of the dam.