Varying type of forage, concentration of metabolizable protein, and source of carbohydrate affects nutrient digestibility and production by dairy cows.

The effects of forage source, concentration of metabolizable protein (MP), type of carbohydrate, and their interactions on nutrient digestibility and production were evaluated using a central composite treatment design. All diets (dry basis) contained 50% forage that ranged from 25:75 to 75:25 alfalfa silage:corn silage. Rumen-degradable protein comprised 10.7% of the dry matter (DM) in all diets, but undegradable protein ranged from 4.1 to 7.1%, resulting in dietary MP concentrations of 8.8 to 12.0% of the DM. Dietary starch ranged from 22 to 30% of the DM with a concomitant decrease in neutral detergent fiber concentrations. A total of 15 diets were fed to 36 Holstein cows grouped in 6 blocks. Each block consisted of three 21-d periods, and each cow was assigned a unique sequence of 3 diets, resulting in 108 observations. Milk production and composition, feed intake, and digestibility of major nutrients (via total collection of feces and urine) were measured. Few significant interactions between main effects were observed. Starch concentration had only minor effects on digestibility and production. Replacing corn silage with alfalfa decreased digestibility of N but increased digestibility of neutral detergent fiber. Increasing the concentration of MP increased N digestibility. The concentration (Mcal/kg) of dietary digestible energy (DE) increased linearly as starch concentration increased (very small effect) and was affected by a forage by MP interaction. At low MP, high alfalfa reduced DE concentration, but at high MP, increasing alfalfa increased DE concentration. Increasing alfalfa increased DM and DE intakes, which increased yields of energy-corrected milk, protein, and fat. Increasing MP increased yields of energy-corrected milk and protein. The response in milk protein to changes in MP was much less than predicted using the National Research Council (2001) model.

Varying forage type, metabolizable protein concentration, and carbohydrate source affects manure excretion, manure ammonia, and nitrogen metabolism of dairy cows.

Effects of forage source, concentration of metabolizable protein (MP), and type of carbohydrate on manure excretion by dairy cows and production of ammonia from that manure were evaluated using a central composite experimental design. All diets (dry basis) contained 50% forage that ranged from 25:75 to 75:25 alfalfa silage:corn silage. Diets contained 10.7% rumen-degradable protein with variable concentrations of undegradable protein so that dietary MP ranged from 8.8 to 12%. Starch concentration ranged from 22 to 30% with a concomitant decrease in neutral detergent fiber. A total of 15 diets were fed to 36 Holstein cows grouped in 6 blocks. Each block was a replicated 3 x 3 Latin square resulting in 108 observations. Manure output (urine and feces) was measured using total collection, and fresh feces and urine were combined into slurries and incubated for 48 h to measure NH3-N production. Feces, urine, and manure output averaged 50.5, 29.5, and 80.1 kg/d, respectively. Manure output increased with increasing dry matter intake (approximately 3.5 kg of manure/kg of dry matter intake), increased concentrations of alfalfa (mostly via changes in urine output), and decreased concentrations of starch (mostly via changes in fecal output). The amount of NH3-N produced per gram of manure decreased with increasing alfalfa because excreted N shifted from urine to feces. Increasing MP increased NH3-N produced per gram of manure mainly because of increased urinary N, but increased fecal N also contributed to the manure NH3. Manure NH3-N production per cow (accounts for effects on manure production and NH3-N produced per unit of manure) was least and milk protein yields were maximal for diets with high alfalfa (75% of the forage), moderate MP (11% of diet dry matter), and high starch (30% of diet dry matter).

Changes in measures of biotin status do not reflect milk yield responses when dairy cows are fed supplemental biotin.

A sensitive indicator of biotin status for lactating dairy cows is necessary to understand factors that affect milk yield responses to biotin supplementation. 3-Hydroxyisovaleric acid (3HIA) is an alternative metabolite in the pathway of Leu catabolism when the biotin-dependent enzyme methylcrotonyl-coenzyme A carboxylase is limiting. We evaluated urinary excretion of 3HIA as a determinant of biotin status in lactating dairy cows. We hypothesized that high-producing cows would have a greater biotin requirement and excrete more 3HIA than low-producing cows and that biotin supplementation would decrease 3HIA excretion. Twenty high-producing and 20 low-producing Holstein cows (43 +/- 5 and 23 +/- 4 kg/d of milk, respectively) were fed diets that contained either 0 or 0.96 mg/kg of supplemental biotin. On d 16 cows were given an intraruminal infusion of 1.4 mol of isovaleric acid and urine was sampled. Biotin supplementation did not affect basal urinary excretion of 3HIA. The infusion of isovaleric acid increased urinary excretion of 3HIA (maximum at 8 h after infusion), but biotin supplementation did not attenuate this increase. The increase in urinary 3HIA excretion was less for low-producing cows than for high-producing cows. Biotin increased yields of milk and milk components in high-producing cows but had no effect in low-producing cows. However, potential measures of biotin status (concentrations of avidin-binding substances in the plasma, milk, and urine, and urinary 3HIA excretion) responded similarly to biotin supplementation for both high- and low-producing cows. A sensitive indicator of biotin status for lactating dairy cows is still needed.

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 of a wide range of compounds. This study was conducted to determine absorption 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 DDE, PCB-153, and OCDD either 1 h (n = 2) or 65 h (n = 2) postpartum to determine 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 gram of chromic oxide (Cr2O3) was administered as a digestion marker to dosed calves. Two male calves, receiving only colostrum, served as controls. Serum IgG concentrations indicated that the 1-h calves absorbed 20 to 37% of the ingested IgG and 65-h calves < 2%; therefore, the gut absorption mechanisms had changed by 65 h. Plasma DDE, PCB-153, and OCDD profiles did not differ based on time of exposure, suggesting that their mechanism of absorption was not influenced by the changing gut. Trapezoidal area under the curve to the last time point values indicated that, during the trial, relative plasma organochlorine concentrations amounted to PCB-153 > DDE > OCDD. Tissue 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 detailed clinical observations, serum clinical chemistry, and gross and histological 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 combination at these concentrations.

Effects of dietary crude protein concentration during periods of feed restriction on performance, carcass characteristics, and skeletal muscle protein turnover in feedlot steers.

In Exp. 1, 36 individually penned steers (initial BW = 294 +/- 3.8 kg) were used to determine effects of dietary CP percentage and programming gain on performance and carcass characteristics. Steers were fed to achieve a predicted gain of 1.13 kg/d for the first 84 kg of gain and 1.36 kg/d for the next 124 kg of gain and were offered feed for ad libitum consumption for the final 58 kg of gain before slaughter. In these three phases of growth, steers were fed diets, sequentially, with the following CP percentages: HHH (16, 13.5, and 12.5%), LHH (9, 13.5, and 13%), or LLL (9, 9, and 9%). When predicted gain was 1.13 kg/d, ADG was greater (P < 0.01) for steers in the HHH (1.09 kg/d) vs LHH and LLL (0.83 kg/d) systems. When predicted gain was 1.36 kg/d, ADG and gain efficiency were greatest (P < 0.01) for steers in the LHH system. Overall ADG and gain efficiency were greater (P < 0.01) for steers in the HHH (1.46 kg/d, 0.194) and LHH systems (1.38 kg/d, 0.190), compared with steers in the LLL (1.21 kg/d and 0.166) system. Carcass fat thickness was lower for steers in the LHH (0.74 cm) system than for steers in the LLL system (1.09 cm). In Exp. 2, 18 individually penned steers (initial BW = 225 +/- 5.8 kg) were either offered a 13% CP diet for ad libitum intake (AL) throughout the 134-d experiment or fed a high- (16% CP; PI-HH) or low- (10% CP; PI-LH) CP diet and fed to achieve a predicted gain of 1.13 kg/d for the first 85 d of the experiment. Steers in the PI-HH and PI-LH feeding regimens were then offered a 13% CP diet for ad libitum consumption from d 86 to 134. Fractional protein accretion rate was greater (P < 0.01) for steers in the PI-HH and PI-LH feeding regimens than for steers in the AL regimen at d 92, 106, and 120. Fractional breakdown and synthesis rates were not affected (P = 0.63) by feeding regimen. Increased ADG and gain efficiency of steers during compensatory growth periods may in part be due to greater fractional accretion rates of skeletal muscle protein.

Kinetics of plasma fructose and glucose when lactose and fructose are used as energy supplements for neonatal calves.

Shortly after birth, plasma glucose and fructose concentrations of the neonate decline and thus leave blood sugar below the homeostatic mode. Two trials were conducted to determine the plasma glucose and fructose kinetics in control and supplemented calves for 108 h after birth. In the short-term trial, six Holstein calves were given 40 g of either fructose, lactose, or water (control) orally at 1 and 96 h after birth. Treatments were administered with a colostrum substitute (Life Boost) at 1 h and whole milk at 96 h. Rectal temperatures and changes in plasma glucose and fructose concentrations were monitored at close intervals for 12 h after supplementation. In the long-term trial, 15 Holstein calves were given 40 g of either lactose, fructose, or water (control) at 1 h after birth and at 12-h intervals for 81 h. Plasma glucose and fructose concentrations were determined before and 4 h after each of the seven feedings. Early postpartal feeding of fructose suppressed plasma glucose (approximately 50%), with a reciprocal rise in plasma fructose. Irrespective of treatment, plasma glucose concentrations did not stabilize (approximately 100 mg/dL) until 17 to 24 h after birth. After 24 h, lactose supplements increased concentrations of plasma glucose 4 h after supplementation (169.7 +/- 8.2 mg/dL), compared with those in calves that did not receive the additional lactose. After 24 h, fructose supplements did not affect plasma glucose, but plasma fructose concentrations increased (82.6 +/- 12.4 mg/dL) 4 h after administration. The response to fructose supplements declined by 11.4 mg x dL(-1) x d(-1). Fructose was not detected in the plasma of control or lactose-treated calves after 17 h after birth. Calves that received fructose supplements had rectal temperatures 8 and 10 h after birth that were higher than those of the other calves. The mechanisms of sugar metabolism change quickly following birth. Oral sugar supplements increase the total plasma sugar concentrations of treated calves.

Mechanisms of movement of organochlorine pesticides from soils to cows via forages.

When cattle were allowed to graze land previously used as orchards, residues of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] were detectable in milk fat and adipose tissues. Concentrations of DDE exceeded .3 micrograms/g at times. Concentrations of DDE in adipose tissue were similar to those in milk fat at the beginning of lactation; residues in first lactation cows were approximately three times higher than in multiparous cows that were grazing similarly. Based on the equation [DDE, micrograms/g]milk fat = .28 (daily dose, mg).82, consumption of soil was likely not the sole source of residue when soil concentrations of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane], DDE, and DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane] ranged from non-detected to 3.6, 2.1, and .655 micrograms/g, respectively. Grass appeared to be the likely source. Four plots were located on three orchard locations and one control location. Grasses in subplots were harvested at 2-, 4-, or 6-wk intervals during the 18-wk study. Grasses were extracted differentially to determine DDT and DDE residues adhering to the plant surface and those associated with plant tissue. Surface residue was not significant. The DDE averaged between .01 and .11 micrograms/g in dry grass tissues. Differences between residues in grasses among plots were associated with soil residue concentrations. Concentrations of DDE were not associated with air or soil temperature, relative humidity, solar radiation, or dry biomass harvested. Precipitation increased the volatilization of residues from soil and deposition in 2- and 4-wk grass samples.(ABSTRACT TRUNCATED AT 400 WORDS)

The clearance of carbon-14-fructose, carbon-14-glucose, and carbon-14-sorbitol by calves at birth and 7 days of age.

Prior to birth, the calf is solely dependent on maternal energy sources. Dramatic changes in blood concentrations of carbohydrates, hormones, and enzymes occur, enabling the neonate to achieve homeostasis. Many of these changes are not well understood. This study was to monitor the metabolism and disappearance of labeled carbohydrates in conjunction with endogenous fructose and glucose. Calves were infused intravenously with 100 muCi of [U-14C]D-fructose, -glucose, or -sorbitol within 12 min of birth and at 7 d of age. Close-interval blood and urine samples were collected until 720 min postinfusion. Radiolabel from the three carbohydrates was separated into parent compound fractions of HPLC. Concentrations of cortisol, insulin, glucose, and fructose were determined from blood. Serum cortisol concentration was 3 to 10 times higher in calves at birth than at 7 d of age. Serum insulin concentrations increased postfeeding in newborn and 7-d-old calves. Insulin concentrations were related to plasma glucose. Endogenous plasma fructose was 63 mg/dl (SE = 7) at birth and was undetectable after 14 h. Glucose was 60 mg/dl (SE = 1) and 92 mg/dl (SE = 8) at birth and at 7 d, respectively. Clearance of radiolabel from glucose at birth and for all the carbohydrates at d 7 was similar. Fructose and sorbitol were cleared more slowly at birth. Radiolabel from fructose at birth was converted very slowly to glucose, but this conversion was rapid at d 7. Sorbitol was converted to fructose at birth but changed quickly to glucose at d 7. The 24-h excretion of radiolabel in urine was less than 4% for fructose and glucose at birth and at d 7. The label from sorbitol appeared in urine at birth (32%) and at d 7 (10%). A source of fructose may provide a slowly utilizable energy source until blood glucose concentrations become stable in the newborn calf.

Carbohydrate, enzyme, and hematology dynamics in newborn calves.

The dynamics of 25 blood constituents in newborn calves were monitored. Eight calves were immediately removed from dams following birth. Jugular blood samples for carbohydrate determinations were taken at birth (within 2 min), 1, 3, 6, 8, 12, 18, and 24 h and every 12 h until 144 h of age. Samples for blood chemistries were taken at birth, 1, 3, 6, 12, 24, 48, 72, 120, and 144 h. Colostrum was first fed at either 1 h (group 1) or 12 h (group 2) of age. At birth, plasma glucose concentrations were lower than the plasma fructose in both groups. Plasma glucose increased substantially from birth to 24 h, whereas fructose decreased to nondetectable concentrations by 18 h. Increases in insulin were associated with time of first feeding. Serum cortisol decreased rapidly from birth to 3 h for group 1 and at 15 h for group 2. Colostrum intake resulted in increased activities of serum alkaline phosphatase, gamma-glutamyl transpeptidase, and glutamic oxaloacetic transaminase at 6 h for group 1 and at 15 h for group 2. Activities of these enzymes decreased to "normal" values after 24-h samplings for group 1. Serum glutamic pyruvic transaminase and lactate dehydrogenase increased gradually in activity over the first 24 h in both groups and decreased after 24 h for group 1. Triglycerides and cholesterol increased from birth to 24 h in both groups and continued to increase in group 1 until 144 h. Creatinine decreased and bilirubin increased from birth to 24 h in both groups. These changes indicated that the newborn calves were undergoing many adaptive changes in relation to either maintenance of homeostasis or nutrient intake.

Reevaluation of polychlorinated biphenyl concentrations in milk and body fat of lactating cows.

Polychlorinated biphenyls occur as mixtures of congeners, each of which may be absorbed, excreted, or metabolized differently. Quantification of polychlorinated biphenyls by packed-column GLC has been difficult. Many quantification techniques, generally based on quantification of a selected group of the congeners present, have been used by researchers. Results of these studies have not provided a consistent basis to determine the relationship between the amounts of polychlorinated biphenyls consumed and residual polychlorinated biphenyls in milk and animal tissues. In the present study, we hypothesized that if a standardized quantification procedure was applied, consistent dose:residue predictions could be made. Weighted percentage of each peak in the polychlorinated biphenyl mixture procedures was used as a standard method to quantify polychlorinated biphenyls in milk fat from published and unpublished studies where lactating cows were fed between 3.5 and 1000 mg/d (Aroclor 1254) for greater than or equal to 15 d. When steady state occurred by 60 d of dosing, the relationship between concentration in milk fat (microgram/g) and daily dose as mg and as mg/kg BW were described by the equations: [polychlorinated biphenyls, microgram/g]milk fat = .28 (daily dose, mg).82, and [polychlorinated biphenyls, microgram/g]milk fat = 50.2 (daily dose, mg/kg BW).81. Similar equations described the relationships between daily dose and concentrations in adipose tissue and blood plasma. Concentrations of polychlorinated biphenyls residues in milk fat of 79 animals that were dosed with known quantities of polychlorinated biphenyls for 15 to 107 d confirmed that the equations could be valuable in predicting exposure over a wide range of exposure durations and concentrations.

Effects of halogenated hydrocarbons on rumen microorganisms.

Halogenated hydrocarbons such as polychlorinated biphenyls (PCB's), heptachlor (HEP), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane (DDT), and pentachlorophenol (PCP) are environmental contaminants and, at times, can bioaccumulate in the food chain. Cattle have been contaminated in a variety of ways, but generally it is believed that they are only affected by high concentrations of the chemicals. Rumen microorganisms, however, may be affected at lower doses, thus possibly affecting the cow's growth and milk production. Polychlorinated biphenyls, HEP, DDT, and PCP were tested by a 1-stage in vitro fermentation procedure. Substrate utilization was determined by measuring percent dry matter disappearance. Four concentrations (0, 10, 50, and 100 ppm) were studied, and in vitro incubations were conducted for 24 and 48 hr. Samples were removed from 48-hr incubations to determine if the chlorinated hydrocarbons were metabolized during fermentation. Dry matter disappearance proved to be a reliable method to determine microbial activity in the presence of chemicals. Substrate dry matter disappearance for controls and all concentrations of PCB's, HEP, and DDT was approximately 50 and 80% at 24 and 48 hr, respectively. The PCP significantly (P less than 0.05) depressed the percent dry matter disappearance in 50- and 100-ppm cultures to 45 and 30% at 24 hr and 70 and 50% at 48 hr, respectively. Metabolic changes in the test chemicals were not detected by gas chromatographic analysis.

Health and productivity of dairy cows fed polychlorinated biphenyls.

Holstein cows were studied through a complete lactation, a nonlactating period, and 42 days of a subsequent lactation for overt and subtle responses to a commercial mixture of polychlorinated biphenyls. Dosed cows (n = 4) received consecutive 60-day periods of daily dosing with 10, 100, and 1000 mg of Aroclor 1254. Control cows (n = 6) received daily sham doses. The following were recorded: daily milk production, feed intake, and health observations; weekly body weight, temperature, heart and respiratory rates and rectal palpation; semi-monthly clinical chemistry determinations; and monthly milk fat, microbiological culture of quarter foremilk samples, and composite milk somatic cell counts. Mean daily milk production (22.4 +/- 1.1 vs 24.8 +/- 1.0 kg) and net energy of a complete lactation (1.46 +/- 0.05 vs 1.45 +/- 0.03 Mcal/kg dry matter intake) were not different (p = 0.85) for control and PCB-dosed cows. Milk production during the first 42 days of the subsequent lactation was also similar for control and dosed cows. Occurrences of injuries, dysfunctions, and general infections were not related to polychlorinated biphenyl exposure. Intramammary infections were detected for both lactations with 51 and 32 infections detected in microbiological cultures, respectively, for the control and dosed groups. Environmental pathogens were most frequently isolated from cases of clinically apparent mastitis. The majority of quarter infections detected were due to Corynebacterium bovis. Only one animal (dosed, necropsy revealed left oviduct obstructed) failed to conceive with three to six services required before conception for the other control and dosed cows. Exposure to polychlorinated biphenyls resulting in maximal residues in milk fat, near 100 micrograms/g, had no apparent effect on health and productivity.

Serum isocitrate dehydrogenase during polybrominated biphenyl toxicosis in dairy cattle.

Bovine serum isocitrate dehydrogenase (sICDH) was investigated in dairy cattle as a clinical measurement indicative of hepatic injury. Conditions for optimization of isocitrate dehydrogenase assays for bovine serum are described. Assays of sICDH in normal cattle show average activities of .814 (SD = .202) units/ml serum with a range of .316 to 1.268 for 83 samples taken from 32 animals. Investigation of sICDH in pregnant dairy cattle experimentally dosed with polybrominated biphenyl (PBB) showed no discernible elevations until doses were sufficient to cause toxicosis (25,000 mg PBB/d). Cows lethally dosed with 25,000 mg PBB/d had moderate elevations of sICDH (approximately a twofold increase) concomitant with severe toxicosis in some but not all animals. This PBB dose also caused abortion or fetal death in pregnant animals; elevation of sICDH in these animals was coincident with fetal trauma. This suggests that sICDH may be influenced by fetoplacental contributions in pregnant animals. Non-pregnant cows, intoxicated with PBB, had minimal sICDH elevation as compared with 10-fold in a calf with experimentally induced hepatotoxicity (thioacetamide). This observation was consistent with histopathological findings of minimal, if any, hepatic involvement in dairy cattle lethally intoxicated with PBB. Serum isocitrate dehydrogenase appears to be a useful adjunct to the ordinary complement of serum chemistries used for clinical diagnosis; however, it does not appear to reflect exclusively hepatic injury.

Changes in hepatic function tests to induced toxicity in the bovine liver.

Graded hepatic damage was induced in mature lactating dairy cows to measure the sensitivity of several hepatic diagnostic tests. In a preliminary study, cows were dosed with .05, .10 and .20 ml/kg body weight of carbon tetrachloride. Extreme changes occurred in hepatic tests by 24 h post-dosing, and all died by 35 h with massive diffuse centrilobular necrosis of hepatic cord cells. Dosing was decreased to induce non-fatal hepatic changes. Cows in Groups 1, 2, 3 and 4 were orally dosed with .002, .004, .006 or .01 ml/kg body weight of carbon tetrachloride, respectively. Serum enzymes of hepatic origin, bilirubin, plus bromosulfophthalein dye clearance were assayed before dosing and up to d 14 post-dosing. Liver biopsies were performed 24 h post-dosing for histological evaluation and cytochrome P-450 content. Hepatic concentrations of cytochrome P-450 were decreased in all the dosed cows. Serum activities of sorbitol dehydrogenase and gamma-glutamyl transferase were elevated in cows of Groups 3 and 4 and glutamic-oxaloacetic transaminase in cows of Group 4 by 24 h. Serum alkaline phosphatase, glutamic-pyruvate transaminase, lactate dehydrogenase, bilirubin, urobilinogen and bromosulfophthalein dye clearance were not significantly different. Mild to moderate diffuse centrolobular necrosis was observed in livers of cow of Groups 3 and 4, but no pathological changes were seen in Groups 1 and 2.

Effects of polybrominated biphenyls on the concentration and clearance of steroids from blood.

Hepatic microsomal mixed-function oxidases have been stimulated when cattle were experimentally fed polybrominated biphenyls (PBB; fireMaster BP-6). These changes provide mechanisms for alteration of the metabolism and clearance of steroid hormones that might then affect reproductive function. This study was conducted to examine the effects of PBB on the clearance of radiolabel from injected estradiol-17 beta and progesterone along with daily determinations of concentrations of endogenous estradiol-17 beta and progestins in blood plasma. Toxicity was induced by dosing two Holstein cows with 25 g of fireMaster BP-6/d for 39 or 50 d. Single iv injections of 35 microCi [4-14C] progesterone and 400 microCi [2,4,6,7-3H] estradiol-17 beta were given on d -5, 10, 30 and 38 or 48 relative to dosing. Last injections were given when severe toxic symptoms were observed in each animal. Clinical signs, blood constituents, and necropsy findings confirmed the toxic syndrome. Clearance of 14C from progesterone was described by a biexponential function of time, while 3H from estradiol was cleared more slowly with a triexponential function. The total clearance rate for radiolabel from progesterone was approximately four times greater than estradiol throughout the experiments. The total clearance rates were similar for both steroids before and 10 d after dosing with PBB. A toxic syndrome was well developed by d 30 of PBB dosing and the total clearance rate of both steroids decreased approximately 50% with precipitous decreases when animals were terminally toxic. Despite the developing toxic syndrome, plasma concentrations of estradiol-17 beta and total progestins were normal and the periodicity of estrous cycles was maintained.

Effects of polybrominated biphenyls on the excretion of steroids.

When polybrominated biphenyls (fireMaster BP-6, PBB) are ingested by cattle, they have been shown to alter hepatic enzyme systems, and produce renal lesions with chronic high exposure. These changes provide mechanisms for alteration of the metabolism and clearance of steroid hormones that might then affect reproductive function. This study was conducted to examine the effects of PBB on the excretion of radiolabel from injected estradiol-17 beta and progesterone. Toxicity was induced by dosing two Holstein cows with 25 g of fireMaster BP-6/d for 39 or 50 d. Single iv injections of 35 microCi [4-14C] progesterone and 400 microCi [2,4,6,7-3H] estradiol-17 beta were given on d -5, 10, 30 and 38 or 48 relative to dosing. Last injections were given when animals were terminally toxic. Clinical signs and necropsy findings confirmed the typical toxic syndrome and renal lesions. Excretion of 14C was primarily in feces, while 3H appeared in both urine and feces. As toxicosis developed, the excretion of steroids in feces was delayed as anorexia reduced mass and rate of passage of feces. This had little effect on the amount of steroid excreted and the rate of urinary excretion was affected only minimally. Recovery of both radiolabels declined 10 to 20% by d 30 of dosing as excretion rate was reduced from pre-PBB dosing. Excretion declined sharply when animals were moribund. Despite developing toxicosis, both animals continued to have estrous cycles with normal periodicity.

Host defense systems in cattle exposed to polybrominated biphenyl.

In vivo and in vitro immunologic studies were undertaken in 114 Holstein cattle, 60 of which had detectable polybrominated biphenyls (PBB) in adipose tissue. The tissue PBB concentrations were between 0.02 and at least 1,000 mg/kg. An immunologic test profile was used to evaluate the influence of PBB on bovine immune competence. The profile included serum immunoglobulin determinations, autoantibody studies, lymphocyte subpopulation determinations, lymphoblastogenesis assays, delayed hypersensitivity skin testing, and neutrophil function studies. The results of the evaluation indicated that the host defenses are intact, both in quantity and function, in cattle with PBB body burdens ranging from 0.02 and 24.0 mg/kg for at least 2 years. Cattle fed 25 g of PBB daily during the acute toxicity study exhibited usual immune competence until they accumulated 500 g of PBB (tissue concentrations exceeding 1,000 mg/kg). Cattle that were fed more than 500 g of PBB became moribund and exhibited changes in neutrophil function tests and serum antibody titers.

Performance and health of offspring of cows experimentally exposed to polybrominated biphenyls.

Offspring of cows experimentally given polybrominated biphenyls(fire-Master BP-6) were studied from May 1976 through January 1981. Daily doses were 0,.25, and 250 mg for 60 days for Groups I, II, and III, and 250 mg for 180 or 202 days for Group V. Concentrations of polybrominated biphenyls in fat of dosed animals in Groups I, II, and III, and V were .05, .20, 25, and 30 micrograms/g at the end of dosing. Residue concentrations in body fat declined with a half life of about 1 yr. Seventy-five calves were born to these cows and their offspring, representing first through fifth parturition. Fifteen calves died, 10 of which were in Groups III and V. All deaths in Groups III and V were attributable to dystocia. Incidence od dystocia and calf mortality were related to birth weight of the calf which in turn was correlated with concentrations of polybrominated biphenyls in blood and tissues of the dam. Other variables that influenced birth weight were sex of calf, length of gestation, and parturition number of dam. There were no significant differences in growth and performance of calves from the four dosed groups. Clinical signs of polybrominated biphenyl toxicosis were not evident, and general health of offspring was not influenced. Number of inseminations for conception was greater among offspring from Groups III and V. Mechanisms for this dysfunction have not been determined.