Radioimmunoassay of the anabolic agent zeranol. V. Residues of zeranol in the edible tissues, urine, faeces and bile of steers treated with Ralgro.

Two trials were conducted on steers implanted with zeranol (Ralgro) to determine the edible tissue residues and the secretion pattern in faeces, urine and bile of zeranol residues throughout and beyond the recommended withdrawal period (70 days) for this drug. In the first trial there was considerable variation in the zeranol residue concentration in all edible tissues, the highest concentrations found in the liver being significantly above the control values (P less than 0.05). In the other tissues, only fat sampled 14 days after implanting was significantly above the control value (P less than 0.05). The zeranol concentration in bile samples obtained at slaughter [70 days (18), 90 days (5) and 120 days (2)] were all higher than the apparent concentration in the bile of untreated steers. The mean concentration of zeranol in the faeces and urine varied from day to day and between animals sampled on the same day following implantation. The highest mean concentrations were observed during the first 40 days following implanting, declining steadily to approach the control values 70 days after implantation. The second trial using steers prepared with bile duct re-entrant cannulae resulted in a similar pattern of zeranol excretion in bile, faeces and urine. The highest concentrations of zeranol were observed in bile and ranged from 24 to 34 micrograms/l; there was considerable variation between animals and within animals sampled on successive days. Although the concentration declined steadily, zeranol was still readily detectable 120 days after implanting.(ABSTRACT TRUNCATED AT 250 WORDS)

Radioimmunoassay of the anabolic agent zeranol. III. Zeranol concentrations in the faeces of steers implanted with zeranol (Ralgro).

Using a monoclonal antibody raised against zeranol, a radioimmunoassay has been validated for the determination of zeranol residues in the faeces of treated steers. The limit of decision defined as the mean apparent concentration of zeranol in the faeces of untreated cattle + 3 SD was 1 ng/g faeces. In a trial in which 27 steers were implanted with zeranol (36 mg) at the base of the ear and six steers were sham implanted, the mean maximum concentration of zeranol in faeces was 5.8 ng/g on Day 15 following implanting, declining to 1.67 ng/g on Day 34 following implanting. During this period there was a marked variation between animals sampled on the same day following implanting. At no time during the trial did the apparent concentration of zeranol in the faeces of untreated animals rise above 0.91 ng/g, which is below the limit of decision for this assay.

Barium selenate injections in cattle: effects on selenium concentrations in plasma and liver and residues at site of injection.

Twenty Angus cross heifers were fed a complete diet which contained 0.07 mg selenium/kg dry matter. Thirteen were injected subcutaneously with barium selenate at a dose rate of approximately 1 mg selenium/kg bodyweight and seven remained untreated. All the heifers were slaughtered during the following 121 days, the last of the treated group 119 days after injection. Glutathione peroxidase activity in blood increased within four weeks of administration and remained high thereafter. The selenium dependent glutathione peroxidase activity did not increase in liver kidney or muscle. The concentrations of selenium in the blood, liver and muscle were increased significantly from 30 days until 119 days. Between 76 and 99 per cent of the selenium injected remained at the site of injection.

Boluses of controlled release glass for supplementing ruminants with cobalt.

Boluses of controlled release glass containing cobalt and weighing approximately either 60 g or 14.5 g were administered to 22 steers and 21 sheep respectively. The steers were housed and slaughtered at intervals between 17 and 145 days after dosing. The boluses released more than 0.85 mg cobalt daily. In both untreated and dosed animals serum and liver vitamin B12 concentrations were at the upper end of the normal range. Two types of glass were administered to sheep. In five wethers one glass released 0.07 mg cobalt per day, and in 16 grazing lambs a second glass released more than 0.15 mg cobalt per day. Fourteen of the boluses were recovered from the lambs up to 276 days after dosing. The concentration of B12 in serum of lambs increased significantly from a mean +/- sd of 1.64 +/- 0.47 to 2.02 +/- 0.04 ng/ml serum and the concentration in liver from 3.84 +/- 0.85 to 4.99 +/- 0.72 micrograms/g dry weight liver.

Boluses of controlled release glass for supplementing ruminants with copper.

A controlled release glass was formulated into boluses weighing approximately 17 g or 75 g and administered to 19 lambs and 20 steers respectively. The animals were at pasture during the summer months. The lambs were slaughtered between 57 and 219 days after dosing when the mean concentration of copper in their livers had increased to 107.8 +/- 33.4 mg copper/kg fresh weight compared with 55.9 +/- 23.0 mg copper/kg fresh weight in undosed controls. The steers were slaughtered more than 140 days after dosing; the mean concentrations of copper in plasma had increased and the mean concentration of copper in liver was significantly greater than in undosed control steers (14.1 +/- 4.8 mg copper/kg fresh weight liver in dosed steers, 4.7 +/- 1.4 mg copper/kg in control steers) and was similar to the concentration in steers which had received 200 mg copper as copper calcium edetate (18.2 +/- 4.2 mg copper/kg fresh weight). In sheep the minimum rate of release of copper into the reticulorumen was 2.1 mg/day and in steers 11 mg/day.

Parenteral methods of supplementation with copper and selenium.

Parenteral treatments can provide a rapid successful method of supplementing ruminants with copper and selenium, and avoid the possible interactions between an oral supplement and other dietary constituents. The copper preparations studied contained copper complexed with calcium edetate (EDTA) or copper methionate , copper oxide or copper oxyquinoline sulphonate. The recommended doses of these commercial preparations contain different amounts of copper only part of which is transferred to the liver stores from which it can be released during the following months. The recommended dose of copper oxyquinoline sulphonate contains only 12 mg copper and the duration of its protective effect is short. Only a small proportion of the copper in copper methionate and copper oxide is transferred to the liver whereas nearly all the copper in a single dose of the EDTA complex (50 mg copper for sheep) is transferred to the liver stores. Although no longer recommended for use in sheep the copper EDTA complex can be administered to cattle to provide up to 1 mg copper/kg bodyweight. Selenium deficiency in both cattle and sheep can be corrected by the subcutaneous administration of up to 0.15 mg selenium/kg bodyweight as sodium selenate. However, if a dietary deficiency persists copper and selenium treatments are effective for only a few months. To avoid the need for repeated treatments, slowly dissolving or controlled release systems have been developed. Subcutaneous depots of barium selenate have been used (1 mg selenium/kg bodyweight) but large residues remained at the site of injection for up to three months. Initial trials with controlled release glasses containing copper have shown that they maybe useful for routine parenteral therapy.

Effects of selenium and copper supplementation on the growth of beef steers.

During the grazing seasons of 1978 and 1979, 126 Hereford cross Friesian and 25 Charolais cross Friesian steers were used in controlled trials of the effects of injecting them with copper and, or, selenium. In both seasons the unsupplemented steers had low blood concentrations of copper, selenium and glutathione peroxidase, whereas the supplemented steers maintained their serum copper concentrations within the normal range and had significantly higher whole blood concentrations of selenium and glutathione peroxidase than the unsupplemented animals. Supplementing the steers with 400 mg copper during 1978 increased their growth rate by 0.032 kg/day and supplementing them with 200 mg copper during 1979 increased it by 0.080 kg/day. Supplementing the steers in each year with two doses of selenium, each of 0.15 mg selenium/kg bodyweight, increased their growth rate by 0.041 kg/day in 1978 and by 0.060 kg/day in 1979. There was no interaction between the selenium and copper treatments and the total increases in liveweight gains due to both supplements were around 11 kg in 1978 and 16 kg in 1979.

Bile flow, bile salt secretion and the excretion of iron, copper, zinc and manganese in the bile of calves infected with Fasciola hepatica.

The rate of flow of bile and the concentrations of iron, copper, zinc and manganese in bile were measured in four bull calves, before and for at least 23 weeks after infection with 1000 metacercariae of Fasciola hepatica. Bile flow rate began to increase about 10 weeks after infection and had increased nearly three-fold by 23 weeks but bile salt (total-cholate) secretion rate remained similar to that of two control calves. The excretion of iron in bile increased rapidly eight weeks after infection from a mean of 21.5 nmol per minute to reach 469 nmol per minute at 14 weeks and this increase was accompanied by an increase in gamma-glutamyl transpeptidase activity in plasma. 59Fe studies showed that most of the iron in the bile of infected calves was derived from red blood cells. There were no changes in the excretion of zinc, copper or manganese in bile which could be associated with the infection.

Maximum capacity of the bovine liver to remove manganese from portal plasma and the effect of the route of entry of manganese on its rate of removal.

The rate of uptake of manganese by the liver was measured during infusions of manganese into either the visceral or the systemic circulation of four cows surgically prepared with cannulae in a mesenteric vein, the portal vein and a hepatic vein and in one carotid artery. In three experiments the maximum capacity of the liver to remove manganese from plasma was measured by infusing manganese chloride solution into a mesenteric vein at increasing rates for six hours. In two experiments the rate of uptake of manganese by the liver was determined during infusions of manganese chloride solution into a jugular vein for six hours at a constant rate. Virtually all the manganese infused into a mesenteric vein was cleared during its first pass through the liver, up to a maximum rate (mean +/- SEM) of 97.1 +/- 14.1 mumol per minute or 12.7 +/- 2.3 mumol per minute per kg of liver weight. However, when manganese was infused into a jugular vein at rates less than this maximum rate of uptake only approximately 50 per cent of the manganese in portal plasma was removed during a single passage through the liver.

Study of combined injections of 1 alpha-hydroxy-cholecaldiferol and cloprostenol in the prevention of parturient paresis.

Dairy cows were injected with 1 alpha-hydroxycholecalciferol (1 alpha-HCC) and, or, cloprostenol at 275 days of gestation. Blood samples were taken daily from 270 days of gestation until seven days after parturition and analysed for calcium, inorganic phosphate, magnesium and hydroxyproline. In all treated and control cows concentrations of calcium, inorganic phosphate and magnesium decreased around the time of parturition. Concentrations of hydroxyproline increased from the second to the fourth day after parturition. This increase was slightly smaller in cows injected with cloprostenol but was unaffected by 1 alpha-HCC. There was a greater indicence of retained placenta and endometritis in cows receiving cloprostenol. The injection of cloprostenol with 1 alpha-HCC at 275 days of gestation did not prevent milk fever.

Differences between lactating and non-lactating dairy cows in concentration and secretion rate of insulin.

1. Four parameters of insulin metabolism were compared in catheterized lactating and non-lactating Friesian x Ayrshire dairy cows. 2. The four parameters, i.e. arterial and portal-venous concentrations of insulin, and pancreatic output and hepatic uptake of insulin, were approx. 2-, 3-, 3- and 5-fold higher respectively in the non-lactating cows than in the lactating cows in the normal fed state. Statistical significance was not achieved for the differences in magnitude in the case of the latter two parameters, however. 3. All four parameters increased significantly about 4-fold when non-lactating cows were infused intravenously with glucose for 48 h at a rate of 4.2 mmol/min. The parameters also increased in the lactating cows during glucose infusion, but the values reached were substantially lower than in the non-lactating cows and the increases were not statistically significant. 4. Arterial insulin concentrations doubled in the non-lactating cows during a 3 h infusion of propionate into a mesenteric vein, but remained unaltered in the lactating cows. 5. Differences in insulin concentration and output between the lactating and non-lactating cows were not consistently related to differences in either glucose concentration or glucose-entry rate. Arterial propionate concentrations were similar in both groups of cows at all times. 6. It is concluded that in the dairy cow, insulin secretion in response to an insulinotropic agent is diminished during lactation.

Plasma concentrations of ovarian hormones during the oestrous cycle of the sheep and cow.

Measurements were made of the plasma concentrations of testosterone, progesterone and oestradiol-17 beta during the oestrous cycle of the ewe, and of the plasma concentrations of testosterone and progesterone during the oestrous cycle of the heifer. The maximum concentration of progesterone in the heifer was nearly twice that in the ewe. The maximum concentration of testosterone was similar in both species and occurred at the onset of luteolysis; in the ewe the peak concentration of 19.5 ng/ml plasma was significantly greater (P less than 0.05) than the concentrations of testosterone measured during the remainder of the oestrous cycle.

The effect of xylazine and xylazine followed by insulin on blood glucose and insulin in the dairy cow.

The effect of xylazine and xylazine followed 20 minutes later by insulin upon glucose metabolism and plasma insulin concentrations was examined in three cows. After doses of 0.18 mg per kg xylazine given intramuscularly (IM) or 0.15 mg per kg given intravenously (IV) hepatic glucose production increased, plasma insulin concentrations decreased to 25 to 33 per cent of control values, and there was a prolonged hyperglycaemia. When 200 units of soluble insulin were given 20 minutes after similar doses of xylazine there was a rapid fall in blood glucose and a reduction in the rate of glucose production by the liver. Xylazine-induced hyperglycaemia arose from a combination of increased hepatic glucose production and reduced plasma insulin concentrations. Peripheral tissues were still responsive to insulin and when adequate insulin was available blood glucose concentrations rapidly decreased.