A comparison of the effects of electroimmobilisation and, or, shearing procedures on ovine plasma concentrations of beta-endorphin/beta-lipoprotein and cortisol

The effects of electroimmobilisation (EIM) and shearing procedures on the plasma concentrations of beta-endorphin/beta-lipotrophin (beta-EP/beta-LPH) and cortisol were compared in conscious sheep. Serial blood samples were collected from five groups of animals subjected to either EIM during simulated shearing (EIM + SS), SS, EIM, shearing or control procedures. EIM and shearing each caused significant increases in the plasma concentrations of beta-EP/beta-LPH and cortisol. The responses to EIM and shearing were significantly greater than in the control animals but were not significantly different from each other. There were no significant differences in the mean plasma concentrations of cortisol following treatment between EIM and EIM + SS groups or between SS and control groups. However, the plasma cortisol concentrations after treatment in the EIM + SS group were significantly greater than in the SS group.     

Electroimmobilization and ovine plasma cortisol concentrations: effect of current intensity, current duration and diazepam

Whether the increases in plasma cortisol concentrations which are associated with electroimmobilization (E-IM) of conscious sheep are modified by current intensity, current duration or prior treatment with diazepam was assessed. Sheep were electroimmobilized at 30, 40 or 60 mA for one minute and at 40 mA for two or four minutes. After E-IM of one minute's duration, peak plasma cortisol concentrations occurred at 20 minutes and were 39.1 +/- 7.8 ng ml-1 at 0 mA (control), 56.7 +/- 9.6 ng ml-1 at 30 mA, 62.1 +/- 6.9 ng ml-1 at 40 mA and 78.4 +/- 3.2 ng ml-1 at 60 mA. Both the peak plasma cortisol concentrations and the integrated cortisol responses to E-Im were correlated with current intensity (P less than 0.01). The cortisol responses to E-Im at 40 mA for one, two and four minutes were not significantly different and the response to E-IM at 40 mA for one minute was not affected by the administration of diazepam (0.2 mg kg-1 intravenously) 15 minutes before E-IM. These results indicate that the cortisol response to E-IM is directly dependent on current intensity and that adrenocortical activation by E-IM may be minimised by choosing the lowest current at which effective restraint is maintained.     

Effects of chronic lameness on the concentrations of cortisol, prolactin and vasopressin in the plasma of sheep

Plasma cortisol, prolactin and vasopressin concentrations were measured by radioimmunoassay in blood samples from control and lame sheep. The lame sheep were all suffering from naturally occurring clinical cases of footrot and showed all the behavioural characteristics of chronic pain; they were scored for impairment of gait and pathology of the foot and divided into mild and severely lame groups. The severely lame sheep had increased plasma prolactin and decreased plasma cortisol concentrations. Plasma vasopressin was variable and showed no consistent changes with lameness. The relationships between plasma cortisol, prolactin and vasopressin may be a useful index in the assessment of animals experiencing chronic pain, when taken in conjunction with other measurements.     

Effect of naloxone on serum luteinizing hormone, cortisol and prolactin concentrations in anestrous beef cows

Two experiments were conducted with the opioid antagonist naloxone to determine the effect of opioid receptor blockade on hormone secretion in postpartum beef cows. In Exp. 1, nine anestrous postpartum beef cows were used to measure the effect of naloxone on serum luteinizing hormone (LH), cortisol and prolactin concentrations. Cows received either saline (n = 4) or 200 mg naloxone in saline (n = 5) iv. Blood samples were collected at 15-min intervals for 2 h before and after naloxone administration. Serum LH concentrations increased (P less than .01) in naloxone-treated cows from 1.8 +/- .04 ng/ml before treatment to 3.9 +/- .7 ng/ml and 4.2 +/- .5 ng/ml at 15 and 30 min, respectively, after naloxone administration. In contrast, LH remained unchanged in saline-treated cows (1.6 +/- .3 ng/ml). Serum cortisol and prolactin concentrations were not different between groups. In Exp. 2, 12 anestrous postpartum beef cows were used to examine the influence of days postpartum on the serum LH response to naloxone. Four cows each at 14 +/- 1.2, 28 +/- .3 and 42 +/- 1.5 d postpartum received 200 mg of naloxone in saline iv. Blood samples were taken as in the previous experiment. A second dose of naloxone was administered 2 h after the first, and blood samples were collected for a further 2 h. Serum LH concentrations increased (P less than .01) only in cows at 42 d postpartum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electroacupuncture-induced analgesia in sheep: measurement of cutaneous pain thresholds and plasma concentrations of prolactin and beta-endorphin immunoreactivity

Eleven male and 15 female sheep were subjected to electroacupuncture (EA) treatment, using 2 needle loci described in the Chinese veterinary literature as Yao Pang (lumbar region) and San Yang Lu (1 thoracic limb). Noninjurious cutaneous stimuli were applied, using a calibrated pin-prick probe, a clamp, and a contact heat (75 to 95 C) probe. Cutaneous pain thresholds (PT) were quantified in 7 body areas during control (no acupuncture needles and no electrostimulation) and EA experiments, before and after IV injection of naloxone. Using each animal as its own control, each EA experiment was classified as inducing either good or poor anagelsia on the basis of whole-body PT values. Plasma concentrations of immunoreactive beta-endorphin (beta E) and prolactin were quantified in sequential plasma samples collected at 9-minute intervals throughout all experiments. Electroacupuncture at each locus increased (P less than 0.01) PT (ie, caused cutaneous analgesia) in 6 of 7 body areas, and increased (P less than 0.05) plasma concentrations of immunoreactive beta E and prolactin. In EA experiments in which good analgesia was induced, plasma beta E was increased more (P less than 0.05) than in EA experiments in which poor analgesia was induced. This difference was more evident for the Yao Pang locus. Generally, plasma prolactin concentrations were increased more with good analgesia than with poor analgesia for the Yao Pang locus. Electroacupuncture stimulation of the San Yang Lu locus was associated with higher plasma beta E concentrations than that associated with the Yao Pang locus. Increases in plasma prolactin concentrations were comparable between loci.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of furazolidone and nitrofurazone on egg production, on plasma luteinising hormone and on prolactin concentrations in turkeys

1. Furazolidone or nitrofurazone were given orally to laying turkeys at doses of 7.5, 15 or 30 mg/kg for 7 d. Plasma concentrations of luteinising hormone (LH), prolactin (PRL) and egg production were measured before, during and after treatment. 2. Both drugs produced dose-dependent decreases in LH concentration which were statistically significant at doses of 15 and 30 mg/kg. Plasma PRL concentration was significantly increased in birds receiving 15 or 30 mg/kg of nitrofurazone, and tended to increase in the other treated groups, but this was not statistically significant. 3. Egg production was lowered in a dose-dependent manner by both drugs. However, nitrofurazone appeared to be more potent in reducing egg production than furazolidone. 4. Birds given 15 mg/kg of either drug were injected intramuscularly with luteinising hormone releasing hormone (LHRH) at a dose of 5 micrograms/kg and blood was collected immediately before and 30 min after LHRH administration. 5. Nitrofurazone significantly reduced the rise in LH induced by LHRH. Seven days after withdrawing the drug, the LHRH-induced LH release was not significantly different when compared to that in the control group or that seen on day 7 of treatment.     

Effects of exercise intensity and duration on plasma beta-endorphin concentrations in horses

OBJECTIVE: To determine the relationship between plasma beta-endorphin (EN) concentrations and exercise intensity and duration in horses. ANIMALS: 8 mares with a mean age of 6 years (range, 3 to 13 years) and mean body weight of 450 kg. PROCEDURE: Horses were exercised for 20 minutes at 60% of maximal oxygen consumption (VO2max) and to fatigue at 95% V02max. Plasma EN concentrations were determined before exercise, after a 10-minute warmup period, after 5, 10, 15, and 20 minutes at 60% VO2max or at the point of fatigue (95% VO2max), and at regular intervals after exercise. Glucose concentrations were determined at the same times EN concentrations were measured. Plasma lactate concentration was measured 5 minutes after exercise. RESULTS: Maximum EN values were recorded 0 to 45 minutes after horses completed each test. Significant time and intensity effects on EN concentrations were detected. Concentrations were significantly higher following exercise at 95% VO2max, compared with those after 20 minutes of exercise at 60% VO2max (605.2 +/- 140.6 vs 312.3 +/- 53.1 pg/ml). Plasma EN concentration was not related to lactate concentration and was significantly but weakly correlated with glucose concentration for exercise at both intensities (r = 0.21 and 0.30 for 60 and 95% VO2max, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: A critical exercise threshold exists for EN concentration in horses, which is 60% VO2max or less and is related to exercise intensity and duration. Even under conditions of controlled exercise there may be considerable differences in EN concentrations between horses. This makes the value of comparing horses on the basis of their EN concentration questionable.     

Effects of synthetic ovine corticotropin-releasing hormone on plasma concentrations of immunoreactive adrenocorticotropin, alpha-melanocyte-stimulating hormone, and cortisol in dogs with naturally acquired adrenocortical insufficiency.

We evaluated the effect of ovine corticotropin-releasing hormone (CRH) on plasma immunoreactive (IR) concentrations of ACTH, alpha-melanocyte-stimulating hormone, and cortisol in 8 dogs with naturally acquired adrenocortical insufficiency. Of the 7 dogs with primary adrenal insufficiency, 6 had markedly high basal plasma IR-ACTH concentrations and exaggerated ACTH responses to CRH administration, whereas 1 dog that was receiving replacement doses of prednisone at the time of testing had normal basal IR-ACTH concentrations and a nearly normal response to CRH. In contrast, the 1 dog with secondary adrenocortical insufficiency had undetectable basal plasma IR-ACTH concentrations, which failed to increase after administration of CRH. Basal plasma alpha-melanocyte-stimulating hormone concentrations in the dogs with adrenal insufficiency were within normal range and were unaffected by CRH administration. In all 8 dogs with adrenal insufficiency, plasma cortisol concentrations were low and did not increase after administration of CRH. Therefore, stimulation with CRH produced 2 patterns of plasma IR-ACTH response when administered to dogs with naturally acquired adrenal insufficiency. Dogs with primary adrenal insufficiency had high basal plasma IR-ACTH concentrations and exaggerated responses to CRH, whereas the dog with secondary adrenal insufficiency had undetectable basal plasma concentrations of IR-ACTH that did not increase after stimulation with CRH.     

Effect of age and sex on plasma cortisol and dehydroepiandrosterone concentrations in the dog (Canis familiaris)

Limited data exist on age-related physiological variations in plasma concentrations of cortisol and dehydroepiandrosterone (DHEA) in dogs, despite their potential role in the pathophysiology of ageing. This study examined plasma cortisol and DHEA concentrations and cortisol/DHEA ratio variations, according to age and sex in 311 dogs, aged from two months to 16 years. Before adulthood, DHEA concentrations were higher in peri-pubertal males. During adulthood, cortisol and DHEA were higher in males than females. Among females, DHEA was lower in older dogs, but the decrease was observed at an older age in intact than ovariectomised females. Variations in the cortisol/DHEA ratio inversely reflected those of DHEA. Results indicate that testicles are an important source of DHEA in males, and that DHEA is mainly secreted by the adrenal glands in females. The ovaries’ contribution to circulating DHEA appears to be limited, although it may partially compensate an age-related decrease in adrenal secretion.     

Relationships among prolactin binding, prolactin concentrations in plasma and metabolic activity of the porcine mammary gland

The current studies were designed to investigate relationships among prolactin (PRL) binding, PRL concentrations in plasma and metabolic activity of porcine mammary glands. Preliminary studies revealed specific high-affinity binding of oPRL to porcine mammary gland. Conditions for optimal specific binding were similar to those observed for other species. To address the main objectives of the study, four mammary biopsies and blood samples were obtained from each of four gilts during lactogenesis and lactation (d-11, 4, 21 and 42 of lactation) to measure in vitro rates of metabolic activity, PRL binding to mammary membranes and PRL concentrations in plasma. Metabolic activity, as measured by oxidation of glucose or acetate to CO2 and incorporation into lipid, was low during pregnancy, increased two- to five-fold on d 4, and then paralleled the lactation curve for sows. There were highly significant positive correlations between PRL binding and all measures of mammary metabolism when data from pregnancy and lactation were utilized. Coefficients were positive but generally not statistically significant when lactation data only were utilized. During lactation, significant negative correlations were observed between concentrations of PRL in plasma and PRL binding and between PRL in plasma and mammary metabolic rate. These data provide evidence that binding of PRL to its receptor is an important effector of milk production in sows. Furthermore, oPRL is a suitable ligand to quantify PRL binding to porcine mammary tissue.     

Ergotamine alters plasma concentrations of glucagon, insulin, cortisol, and triiodothyronine in cows

Bovine plasma was assayed to determine whether ergotamine, an ergopeptide isolated from endophytic tall fescue, affected cortisol, triiodothyronine, insulin, and glucagon concentrations. In Exp. 1, four heifers received an i.v. bolus injection of ergotamine tartrate (19 microg/kg BW) or saline vehicle in a simple crossover design 2 d after induced luteolysis. Oxytocin (100 USP units) was i.v. administered 4 h after ergotamine or saline. Treatment x time affected (P < .01) respiration rates and plasma concentrations of cortisol, triiodothyronine, insulin, and glucagon. Respiration rates were elevated (P < .01) 2 to 7 h after ergotamine, but they were unchanged after saline. Plasma cortisol concentrations were increased (P < .01) 1 to 3 h after ergotamine but not after saline. Plasma triiodothyronine was elevated 2 h after ergotamine, but it was unchanged in response to saline. Insulin decreased (P < .01) and glucagon increased (P < .01) during the 1st h after ergotamine, but not in response to saline. A second increase (P < .01) of glucagon was observed 3 h after ergotamine. In Exp. 2, six cows were treated with an i.v. bolus injection of ergotamine (20 microg/kg BW) or saline in a simple crossover design 10 d after receiving a s.c. ear implant containing norgestomet. Oxytocin (100 USP units) was i.v. administered 4 h after ergotamine or saline. Treatment x time affected (P < .001) respiration rates, cortisol, insulin, and glucagon and tended to influence (P = .12) triiodothyronine concentrations. Respiration rates were elevated (P < .01) 1 to 7 h after ergotamine but were unaltered by saline. Plasma cortisol was elevated (P < .01) 1 to 5 h after ergotamine, but not in response to saline. Plasma triiodothyronine was elevated (P < .01) 1 to 2 h after ergotamine, but not after saline. Insulin was decreased (P < .01) and glucagon increased (P < .01) within 1 h after ergotamine treatment, but they were not altered by saline. A second increase (P < .01) of glucagon occurred by 4 h after ergotamine. In Exp. 1 and 2, glucagon increased (P < .01) 1 h after oxytocin in saline and ergotamine cows. Results indicate that ergotamine can alter plasma concentrations of hormones that mediate nutrient metabolism and thermoregulation in cattle.     

Comparison of cortisol concentrations in saliva and plasma of dogs

It is increasingly important to have simple, non-invasive indicators of stress in animals. Studies in various species have shown that concentrations of cortisol in saliva relate closely to plasma levels of the free hormone; the aim of the present procedure was to show a similar correlation in the dog. Baseline blood and saliva samples were collected concurrently from six male beagles. Synthetic adrenocorticotrophic hormone was given and further samples were collected at 0.25, 0.5, one, two and 2.5 hours later. The results indicated a statistically significant correlation between the levels of cortisol in blood and saliva. Concentrations in saliva were between 5 and 10 per cent of those in plasma at each collection time. To demonstrate a response to a more natural stimulus, saliva samples were taken from a dog during exposure to a known stressor for that individual. The results showed a marked, delayed increase from baseline which was maintained for at least 0.5 hours after stressing.     

Effect of transportation on cortisol concentrations and on the circadian rhythm of cortisol in gilts

A study was conducted to determine whether the circadian rhythm of cortisol in gilts is disrupted or altered by transport. Sixteen ovariectomized gilts with indwelling jugular catheters were individually penned in an enclosed building (location 1). Blood samples were collected at 0700 and 1900 hours for 6 days. On day 7, gilts in groups of 4 were transported 5.6 km to environmentally controlled chambers (25 C) and were individually penned (location 2). On the day of transport, samples were collected at 0700 hours at location 1, immediately before and after transport in a trailer, after unloading at location 2, and at 1900 hours at location 2. For the first 6 days at location 2, blood samples were collected daily at 0700 and 1900 hours. For the 6 days at location 1, circadian rhythm was evidenced by higher cortisol concentrations in the AM hours than in the PM hours. During transport, serum cortisol concentrations increased (P less than 0.01). Highest concentrations developed at 0.5 hour after unloading; concentrations declined thereafter. During the first 6 days at location 2, circadian rhythm was evidenced by higher serum cortisol concentrations in the AM hours than in the PM hours. Therefore, the transportation of gilts 5.6 km to new pens was a transient stress causing a temporary increase in serum cortisol concentrations, but did not cause a disruption in the endogenous rhythm of cortisol.     

Effect of administration of adrenocorticotropic hormone on plasma concentrations of testosterone, luteinizing hormone, follicle stimulating hormone and cortisol in stallions

In boars and rabbits, administration of adrenocorticotropic hormone (ACTH) results in a testis-dependent, short-term increase in concentrations of testosterone in peripheral plasma. This experiment was designed to assess the short-term effects of a single ACTH injection on plasma concentrations of testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH) and cortisol in stallions. Eight light horse and two pony stallions were paired by age and weight and then one of each pair was randomly assigned to the treatment (ACTH, .2 IU/kg of body weight) or control (vehicle) group. Injection of ACTH increased (P<.01) plasma concentrations of cortisol by approximately twofold in the first 60 minutes; control stallions showed no change (P>.10) in concentrations of cortisol during the blood sampling period. Control stallions exhibited a midday increase (P>.05) in concentrations of testosterone similar to that reported previously; ACTH treatment prevented or delayed this increase such that concentrations of testosterone in treated stallions were lower (P<.05) than in controls 4 to 5 hours after injection of ACTH. Treatment with ACTH had no effect (P<.10) on plasma concentrations of LH or FSH up to 12 hours after injection.     

Effects of intravenous infusion of lipopolysaccharide on plasma micromineral, magnesium, and cytokine concentrations and serum cortisol concentrations in lactating goats

OBJECTIVE: To assess the effects of various doses of lipopolysaccharide (LPS) administered IV on plasma microminerals, magnesium, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-6 concentrations and serum cortisol concentrations in lactating goats. ANIMALS: 6 lactating goats. PROCEDURES: Goats were allotted to 3 LPS-treatment groups: control (0 microg/kg), low LPS (10 microg/kg), and high LPS (50 microg/kg). Rectal temperatures and behaviors of goats were recorded immediately before a 10-minute IV infusion of LPS and at 0.5, 1, 2, 4, 6, 8, and 24 hours after infusion. Blood samples were obtained before IV infusion and at 0.5, 1, 2, 4, 6, 8, and 24 hours after infusion. Plasma zinc, copper, iron, and magnesium concentrations were determined by atomic absorption spectrometry; plasma TNF-alpha and IL-6 concentrations were measured by use of an ELISA; and serum cortisol concentrations were determined by use of a radioimmunoassay. RESULTS: A monophasic fever developed in low-LPS and high-LPS groups. In the low-LPS and high-LPS group, plasma zinc concentrations decreased at 6 hours after infusion; compared with control groups. Plasma iron concentrations were lower at 24 hours after infusion in low-LPS and high-LPS groups than in the control group. Plasma TNF-alpha and IL-6 concentrations were higher in low-LPS and high-LPS groups than in the control group at 1, 2, and 4 hours after infusion. In low-LPS and high-LPS groups, serum cortisol concentrations increased from 0.5 hours onward and peaked at 1 (high-LPS group) and 2 (low-LPS group) hours after infusion. CONCLUSIONS AND CLINICAL RELEVANCE: Following IV infusion of LPS, the immune system is activated, which might affect micromineral homeostatic regulation and, subsequently, the metabolic health of lactating goats.     

Effect of octreotide on plasma concentrations of glucose, insulin, glucagon, growth hormone, and cortisol in healthy dogs and dogs with insulinoma

The inhibitory effect of the somatostatin analogue octreotide on the secretion of insulin could be used in the treatment of insulinoma. However, current information on the effectiveness of octreotide in dogs is conflicting. Therefore, the endocrine effects of a single subcutaneous dose of 50 microg octreotide were studied in healthy dogs in the fasting state (n=7) and in dogs with insulinoma (n=12). Octreotide did not cause any adverse effects. In healthy dogs in the fasting state, both plasma insulin and glucagon concentrations declined significantly. Basal (non-pulse related) GH and ACTH concentrations were not affected. A slight but significant decrease in the plasma glucose concentrations occurred. Dogs with insulinoma had significantly higher baseline insulin concentrations and lower baseline glucose concentrations than healthy dogs in the fasting state. Plasma glucagon, GH, ACTH, and cortisol concentrations did not differ from those in healthy dogs. Baseline plasma insulin concentrations decreased significantly in dogs with insulinoma after octreotide administration, whereas plasma concentrations of glucagon, GH, ACTH, and cortisol did not change. In contrast to the effects in the healthy dogs, in the dogs with insulinoma plasma glucose concentrations increased. Thus, the consistent suppression of plasma insulin concentrations in dogs with insulinoma, in the absence of an suppressive effect on counter-regulatory hormones, suggests that further studies on the effectiveness of slow-release preparations in the long-term medical treatment of dogs with insulinoma are warranted.     

Effect of chronic hypocortisolaemia on plasma cortisol concentrations during intravenous infusions of hydrocortisone sodium succinate in dogs

Intravenous infusions of hydrocortisone sodium succinate (HSS) were given at 0·625 mg kg⁻¹ hour⁻¹ and 0·312 mg kg⁻¹ hour⁻¹ to six dogs. Plasma cortisol concentrations were measured by radioimmunoassay at 0, 15, 30, 45 and 60 minutes and then every 30 minutes for a further five hours. Chronic hypocortisolaemia was induced and maintained with mitotane and the HSS infusions were repeated after 31 and 50 days. No statistically significant difference was observed in the plasma cortisol concentrations after either period of hypocortisolaemia, but the plasma cortisol concentrations tended to be higher in most of the dogs.     

Effects of castration on behaviour and plasma cortisol concentrations in young lambs, kids and calves.

Behavioural and cortisol responses to the husbandry practice of castration with tight rubber rings were investigated in lambs and kids one day after birth and in hand reared calves aged one to seven days. There were three treatments: control handling and blood sampling, castration and, in lambs and kids only, intravenous adrenocorticotrophin injection (ACTH). The integrated cortisol responses (area under the cortisol curve) in lambs and kids were least in control, intermediate in castrated and greatest in ACTH animals. No cortisol responses were detected in control or castrated calves. The incidences of behaviour used to assess the intensity of distress apparently experienced in the different species corresponded generally with the magnitudes of the cortisol responses. Behavioural and cortisol responses together suggested that the distress caused by castration was greatest in lambs, intermediate in kids and least but not necessarily absent in hand reared calves.     

Effects of sexual stimulation, with and without ejaculation, on serum concentrations of LH, FSH, testosterone, cortisol and prolactin in stallions

Six lighthorse stallions with previous sexual experience were used to determine the short-term effects of sexual stimulation (SS; 5 min exposure to an estrous mare), SS plus ejaculation (SSE), and no stimulation (control) on serum concentrations of LH, FSH, testosterone, cortisol and prolactin. Stallions received one treatment per day on d 1, 4 and 7. Treatments were assigned such that each stallion 1) received each treatment once and 2) experienced a unique sequence of treatments. Neither SS nor SSE had any consistent effects on LH or FSH concentrations. Testosterone concentrations during control bleedings increased (P less than .05) with time. This increase was suppressed (P less than .05) by both SS and SSE. Cortisol concentrations increased (P less than .05) immediately after SS and SSE. Cortisol concentrations also tended to increase during the control bleedings, but only in stallions that previously had been exposed to SS or SSE. Prolactin concentrations increased (P less than .05) immediately after SS and SSE and tended to rise during control bleedings in stallions previously exposed to SS or SSE. We conclude that 1) prolactin and cortisol were secreted rapidly in response to SS and SSE, 2) the rise in cortisol concentrations likely suppressed testosterone secretion within the next hour, and 3) stallions appeared to associate the distant sounds of other stallions with their own previous exposure to SS and SSE, resulting in a cortisol response (and perhaps a prolactin response) even in the absence of direct stimulation.