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PubMed1993

The effect of age on phenylbutazone pharmacokinetics, metabolism and plasma protein binding in goats.

Phenylbutazone (PBZ) was administered intravenously as a single dose (10 mg/kg) to adult male and 1-day-, 10-day-, 4-week- and 6 week-old male goats. The plasma concentration of PBZ and its major metabolites oxyphenbutazone (OPBZ) and gamma-hydroxyphenbutazone (gamma-OHPBZ) was measured over time. The elimination half-life (t 1/2 beta) of PBZ decreased from 120 h in the 1-day-old to 16 h in the adult goats. Although the volume of distribution (Vd) did not change significantly during maturation, the total body clearance (Cl B) increased from 2 ml.h-1.kg-1 in 1-day-old to 13 ml.h-1.kg-1 in the adult goats; the increase was 2-fold in the first 10 days of life. Oxyphenbutazone was detectable in the plasma of adult and 6-week-old goats as early as 15 min after PBZ administration. Its peak concentration occurred at 1.5 h (1.6 micrograms/ml) in adults and at 6 h (0.95 micrograms/ml) and 12 h (0.36 micrograms/ml) in 6- and 4-week-old goats respectively. The highest plasma concentration of gamma-OHPBZ was achieved in 4-week-old followed by 6-week-old and adult animals.

Aging↗

PubMed1993

Effect of gonadal hormones on the plasma clearance and metabolite formation of antipyrine in the dwarf goat.

The effect of gonadal hormones on the plasma elimination and urinary metabolite profile of antipyrine was studied in dwarf goats. Female goats were treated with testosterone and male goats were treated with 17 beta-oestradiol. Castrated males were treated with either testosterone or 17 beta-oestradiol. Antipyrine (25 mg/kg, i.v.) was given both before and after the hormonal treatments. The effects of the hormonal status on the plasma elimination of the parent compound were not consistent. This was possibly due to the fact that formation of the main metabolite of antipyrine in the goat, 4-hydroxy antipyrine (OHA), was not affected by sex or hormonal treatment. On the other hand, there were clear effects of hormonal status on urinary excretion of the three other metabolites. In females and castrated males testosterone suppressed the formation of norantipyrine (NORA), 3-hydroxymethylantipyrine (HMA) and 4,4'-dihydroxyantipyrine (DOHA). Intact males produced smaller amounts of these metabolites than females. It is concluded that distinct xenobiotic metabolizing pathways exist in the dwarf goat, which are influenced in their activity by gonadal hormones. This confirms previous findings in rats and mice. The possibility that sex hormones influence drug metabolism in food-producing animals could have consequences for veterinary therapeutics and public health. This study also demonstrates that, when using the antipyrine test for the assessment of hepatic drug metabolism, it is very important to include the determination of metabolites.

Animals↗

PubMed1993

Pharmacokinetic-pharmacodynamic modelling of meperidine in goats (I): Pharmacokinetics.

Plasma and cerebrospinal fluid (CSF) pharmacokinetics of meperidine were investigated after intramuscular (i.m.) or intravenous (i.v.) administration at a dose of 5 mg/kg in adult goats. After i.m. dosing, the plasma profile was best described by a one-compartment open model. In healthy (n = 16) and post-operative (n = 16) goats, the parameters were, respectively: tmax 8.3 +/- 3.9 and 9.2 +/- 5.5 min, Vd 2.763 +/- 1.231 and 3.929 +/- 2.101 l/kg, Clb 0.125 +/- 0.036 and 0.087 +/- 0.025 l/kg/min, Ke 0.0563 +/- 0.0358 and 0.0271 +/- 0.0136 min-1. The plasma profile was best fitted by a two-compartment open model following i.v. injection. In this case, the parameters for healthy (n = 7) and post-operative (n = 13) goats were, respectively: Vd 5.212 +/- 1.992 and 5.085 +/- 2.288 l/kg, Clb 0.096 +/- 0.028 and 0.075 +/- 0.026 l/kg/min, beta 0.0211 +/- 0.0093 and 0.0160 +/- 0.0052 min-1. There were, however, a few individuals with a prolonged elimination phase. Bioavailability of i.m. meperidine was 66.5 +/- 15.8% in healthy (n = 6) goats, but much higher in postoperative (n = 10) ones at 94.6 +/- 30.0%. Meperidine diffused into and out of CSF according to a first-order rate process. The time-course of CSF drug concentration was simulated by a biexponential function. CSF kinetic parameters of i.m. meperidine for healthy (n = 7) and postoperative (n = 13) goats were: elimination rate constant (K(ef)) 0.0269 +/- 0.0131 and 0.0305 +/- 0.0177 min-1, peak CSF concentration time (Tmaxf) 15.9 +/- 5.0 and 17.0 +/- 6.9 min. For the i.v. dosed healthy (n = 6) and postoperative (n = 8) animals, K(ef) was 0.0408 +/- 0.0107, 0.0414 +/- 0.0123 min-1 and Tmaxf was 10.0 +/- 5.0 and 7.7 +/- 2.5 min, respectively. It was demonstrated that an obviously lower peak concentration can be reached significantly later in CSF than in plasma, and the kinetic behaviour of meperidine in plasma is different from that in the CSF, indicating meperidine analgesia might not be predicted by simple extrapolation from the kinetic data.

Animals↗

PubMed1994

Probable post-synaptic alpha 2 adrenergic mediated effect of xylazine on goat uterine motility.

Xylazine has been characterized as a selective alpha 2-adrenoceptor agonist, which has explained its central nervous system depressant and other pharmacological effects. In order to characterize the effect of xylazine on uterine motility during the oestrus cycle in goats, intrauterine pressure changes were recorded in cycling goats using balloon-tipped catheters placed in the uterine horns and connected to pressure transducers and a recorder. The effect of xylazine on myometrial activity was studied by giving increasing doses of the drug (1.0, 10.0, 100.0 or 500.0 micrograms/kg) intravenously (i.v.) to animals either in the follicular or the luteal phase of the cycle. To establish the subtype of alpha adrenergic receptor mediating the action of xylazine, goats were pretreated with either prazosin (1.0 mg/kg, i.v.) or yohimbine (1.0 micrograms/kg, i.v.). To establish whether the effect of xylazine was pre- or post-synaptic, xylazine (100 mg/kg, i.v.) was administered to goats pretreated with reserpine (0.8 mg/kg, i.p.) to deplete presynaptic catecholamine stores. Xylazine induced a significant and dose-dependent increase on uterine motility in cycling goats, apparently mediated by post-synaptic alpha 2-adrenoceptors.

Adrenergic alpha-Agonists↗

PubMed1986

Interference between different serodemes of Trypanosoma congolense in the establishment of superinfections in goats following transmission by tsetse.

When domestic ruminants cyclically infected with Trypanosoma congolense are superinfected with a different serodeme of the same species, an interference phenomenon occurs which delays the development of the second cyclical infection. Experiments were carried out to investigate the influence of the time interval between the two infections on the degree of interference and to follow the course of the superinfection clinically, serologically and histologically. Goats infected with tsetse-transmitted T. congolense IL 1587 were either infected simultaneously or 7, 14, 18, 28 or 35 days later with a different serodeme, T. congolense IL 1180. Skin reactions due to superinfection were either absent or smaller in size and delayed in onset compared with control animals undergoing a primary infection with T. congolense IL 1180 which had been initiated by tsetse fly bites. All animals were treated with the trypanocidal drug Berenil 21 days after superinfection and 3 weeks later challenged with T. congolense IL 1180 using tsetse flies. The goats that had been infected simultaneously with the two serodemes were immune to the homologous challenge, but 11 (85%) of the animals that had been superinfected were not. The effect of interference on the host immune response to T. congolense IL 1180 was most marked in animals superinfected at day 7; thereafter there was evidence that the ability to respond immunologically against secondary infection was gradually recovered. Histological examination of skin removed 7 days after a simultaneous infection of goats with two serodemes, showed trypanosomes and a cellular reaction similar to that following infection with a single serodeme. In skin removed 7 days after superinfection of goats that had been infected for 7 days, the cellular response was less pronounced and trypanosomes were not seen, although by 14 to 16 days numerous trypanosomes were present and there was a marked cellular infiltrate. It is postulated that the presence or absence of a factor induced shortly after initiation of a trypanosome infection in the skin of goats might delay parasite development when metacyclic trypanosomes are deposited by tsetse following superinfection.

Animals↗

PubMedDate not supplied

Influence of different calcium concentrations in the diet on bone metabolism in growing dairy goats and sheep.

The purpose of this study was to investigate, if different Ca concentrations in diets have an influence on bone mineral metabolism in growing goats and sheep. Twelve growing goats and sheep were divided into two groups. The two control groups received 6.1 g calcium/day (nG) and 6.7 g calcium/day (nS) for goat and sheep respectively. The other two groups were fed 17.7 g calcium/day (hG) and 18.5 g calcium/day (hS). Blood samples were taken 2, 4, 5 and 6 weeks after the start of the experiment. In serum Ca and vitamin D were determined and bone metabolism was measured using crosslinked carboxyterminal telopeptide of type I collagen (ICTP), crosslaps, bone-specific alkaline phosphatase and osteocalcin (OC). Bone mineral density (BMD) was quantified using quantitative computed tomography. Bone resorption marker (ICTP) concentrations were significantly different between both groups control sheep/control goat and hS/hG, but no significant differences were evident in the different feeding groups within one species. OC concentrations showed a similar course to ICTP. The goats had significantly higher concentrations compared with sheep. The 1,25 dihydroxyvitamin D (VITD) concentrations in both hCa groups were significantly lower than in the control groups. BMD increased in the hCa groups compared with the control groups with the time, but significant differences were only evident in sheep in week 2. The hCa diet did not induce differences between the groups within one species for all bone markers. The control Ca diet seems to improve the active Ca absorption via VITD whereas the hCa diet leads to a higher amount of Ca apparently digested. Higher BMD was only observed in group hS compared with nS.

Alkaline Phosphatase↗

PubMed2006

Active immunization against leptin fails to affect reproduction and exerts only marginal effects on glucose metabolism in young female goats.

Approximately 150 days before expected breeding time, 12 female goats (3 months of age) were actively immunized against ovine leptin. Booster injections were given throughout the following year. Control animals (n = 6) were sham-immunized. After the first observed oestrus, a buck was introduced and goats were mated. Blood samples were collected twice weekly and frequent blood sampling series were performed on days -15, 76, 153 and 286 relative to the first immunization. Nine of the immunized goats developed titres within 3 months and had elevated serum concentrations of leptin compared with controls (p < 0.0001). Hematological parameters and blood chemistry were not affected by the immunization. No differences were detectable in all reproductive parameters recorded. Serum insulin was higher in immunized goats during the frequent blood sampling series of day 287 after the first immunization. Glucose metabolism was investigated during pregnancy using hyperglycaemic and euglycaemic/hyperinsulinaemic clamps. None of the parameters derived from the clamp studies was different (p > 0.05) between the two groups. During the hyperglycaemic clamp there was a trend (p < 0.15) towards increased insulin concentrations in immunized animals whereas glucose infusion rates were not different between the groups. This indicates decreased insulin sensitivity in immunized goats. Our study describes the ontogenesis of serum concentrations of leptin during growth, puberty and first pregnancy and parturition for the caprine species. The effects of the immunization were not detectable or only marginal and the approach aimed at therefore not effective to investigate leptin action in detail.

Animals↗

PubMed2005

Administration of hCG 5 days after breeding and reproductive performance in nulliparous dairy goats.

The objective of this study was to investigate the effect of hCG administration 5 days after breeding on plasma progesterone (P4) concentration and reproductive performance of oestrous-induced nulliparous dairy goats. A total of 59 nulliparous goats (36 Alpine and 23 Saanen) received intravaginal sponges with 60 mg medroxyprogesterone acetate for 9 days plus 200 IU equine chorionic gonadotrophin (eCG) and 22.5 microg d-cloprostenol 24 h before sponge removal. After detection of oestrus (day of oestrus = day 0) and breeding, 49 females were randomly assigned, according to the breed, into two treatments (T1 and T2). In T1 (n = 25) and T2 (n = 24), animals received intramuscular injection of 1 ml of saline solution (control) or 250 IU hCG, respectively, 5 days after breeding. Plasma P4 concentration (ng/ml) was determined from blood sampled on days 0, 5, 7, 13, 17, 21, 28 and 45 after breeding. Animals were scanned by transrectal ultrasound (5 MHz probe) on days 35 and 70 after breeding for detection of pregnancy. Plasma P4 concentration did not differ (p > 0.05) between treatments in all days, but it was increased (p < 0.05) in Saanen than in Alpine goats from days 13 to 45. Pregnancy and parturition rates, litter size and gestation period were similar (p > 0.05) to treatments and breeds. Results of this study indicate that human chorionic gonadotrophin (hCG) administration 5 days after breeding did not significantly alter reproductive performance in dairy nulliparous goats and that plasma P4 differed between Saanen and Alpine goats.

Animals↗

PubMed2005

Effect of nutrition on plasma progesterone levels, metabolic parameters and small follicles development in unstimulated goats reared under constant photoperiod regimen.

Sixteen local adult goats were submitted for 9 weeks to 2.09 (high group) and 0.54 (low group) x dietary maintenance respectively. During the experimental period, goats were weighed, oestrus was detected and plasma insulin, urea, non-esterified fatty acids and progesterone concentrations were assessed. At the end of the experiment, ovarian small follicles population was studied by histological analysis. Final weight loss in low group was 18.37 +/- 2.02%, whereas weight gain of high group was 13.84 +/- 2.70%. Insulin and urea were lower in low group, while non-esterified fatty acids were significantly higher. A lower number of fasted goats was in oestrus or ovulated and an extended length of oestrus (p < 0.05) and a higher frequency of short or long cycles (p < 0.05) were also observed. Fed animals showed heavier ovaries (p < 0.01) and a lower number of primordial follicles (p < 0.05). In restricted goats a significant qualitative alteration of follicle classes involved in the initiation process of primordial pool was found. In this phase, granulosa thickness and oocyte size were the most affected (p < 0.01). However in small follicles beyond the primary stage no differences were found between the groups in either number or qualitative characteristics (p > 0.05). Collectively, these results indicate that opposite dietary intakes for a medium period induce a composite reproductive response in goats and can regulate the early onset of follicle growth.

Animal Nutritional Physiological Phenomena↗

PubMed2006

Bacteriological findings and hormonal profiles in the postpartum Balady goats.

Twenty-six Balady goats categorized according to parity into primiparous and pluriparous goats were used to investigate bacterial flora of the genital tract and hormonal profiles during the postpartum (PP) period. Escherichia coli and Staphylococcus aureus were isolated in pure or mixed culture from the uterus. Arcanobacterium pyogenes was isolated from swabs obtained from the vagina and cervix of one primiparous goat. Uteri and cervices but not vaginas were free of bacterial contamination by day 10 PP except for one pluriparous goat with scanty E. coli contamination on day 25 PP. Fluctuating oestradiol 17beta (E2) levels demonstrated resumption of follicular activity as early as day 13 PP in both parity groups. Progesterone (P4) levels remained low at basal levels throughout the study period. Higher concentrations of 15-keto-13,14-dihydroprostaglandin F2alpha (PGFM) were observed during the first week PP compared with the rest of the PP period. PGFM concentrations dropped to low basal level by day 10 PP and remained constantly low throughout the study period. P4, E2 and PGFM profiles were not different between the different parity groups. In conclusion, intrauterine infection is not common in goats with normal kidding. E. coli was the most common intrauterine bacterial isolate. E2 and P4 profiles were consistent with resumption of follicular growth but not ovulation. High PGFM concentrations coincided with the fast regression phase of uterine involution. Hormonal profile and bacterial contamination and clearance were similar to those reported in other related species and not related to parity.

Animals↗

PubMed2004

Comparison of biochemical and cytotoxic functions of hepatocytes from goat, pig and human fetuses.

BACKGROUND AND AIM: To overcome the problem of shortage of donor organs, xenotransplantation of cells offers an alternative to orthotopic transplantation. Of the higher animals, the pig is considered as a suitable donor because of the similarity in size and function of pig organs to human organs. However, successful transplantation of pig organs/cells for human therapy is limited by hyperacute rejection, improper functioning of xenografts and the risk of transmission of endogenous retroviruses to the recipient. Thus, there is a pressing need to explore an alternate mammalian source to bridge the gap between the donor and the recipient waiting for transplantation. This has warranted us to explore the application of goat hepatocytes as a treatment modality in acute liver failure. METHODS: In the present investigation, isolated goat hepatocytes were assessed for their viability, membrane integrity, synthetic and cytotoxic functions, and compared with the hepatocytes of pig and human fetuses (28-36 weeks). RESULTS: The isolated hepatocytes from goat, pig and human fetuses were comparable in their viability, membrane integrity and synthetic functions. However, the cytotoxic functions assessed using 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide assay demonstrated a significant reduction in the viability of the pig hepatocytes (38%) as compared with the goat and human fetal hepatocytes, which retained their viability (98%) on incubation with normal human serum. CONCLUSION: These observations are significant as they suggest that goat hepatocytes probably can be explored as a source for cell therapy in the treatment of acute liver failure.

Analysis of Variance↗

PubMed2005

Iliocostalis muscles in three mammals (dolphin, goat and human): their identification, structure and innervation.

Iliocostalis (IC) muscles were studied in four dolphin embryos, three goat embryos and four Japanese adult cadavers through macroscopic dissection. The IC muscles of the dolphin were located on the lateral aspect of the trunk and displayed an intercostal arrangement. In contrast, the IC muscles in both the goat and human showed a double-layered architecture formed by a multisegmental muscle-tendon complex and were located on the lateral and medial sides of the costal angle, respectively. Generally, the nerve to the iliocostalis (NIC) in the dolphin and goat did not form a common trunk with the nerve to the longissimus on the epaxial plane, whereas in humans the NIC ran parallel to the nerve to the longissimus part of the way. The individual NIC ran caudolaterally, innervating the one lower (caudal) metameric division of the IC muscle in the dolphin and piercing the fascia of the IC muscles at a point in the next caudal intercostal level in the goat and human. In the upper thoracic part of the goat and human, the caudal shift of innervation was obscured, where the IC muscles were close to the vertebrae. The course of the NIC was closely related to that of the lateral cutaneous branch. The present study shows that the NIC is commonly destined for the one lower intercostal level among the three mammalian species, with their respective IC muscles having distinctly different structural complexity.

Animals↗

PubMed2005

A comparison of propofol, thiopental or ketamine as induction agents in goats.

OBJECTIVE: To compare propofol, thiopental and ketamine as induction agents before halothane anaesthesia in goats. STUDY DESIGN: Prospective, randomized cross-over study. Animals Seven healthy adult female goats with mean (+/-SD; range) body mass of 38.9 +/- 3.29 kg; 35-45 kg. METHODS: The seven animals were used on 21 occasions. Each received all three anaesthetics in a randomized cross-over design, with an interval of at least 2 weeks before re-use. Anaesthesia was induced with intravenous (IV) propofol (3 mg kg(-1)), thiopental (8 mg kg(-1), IV) or ketamine (10 mg kg(-1), IV). Following tracheal intubation, anaesthesia was maintained with halothane for 30 minutes. Indirect blood pressure, heart rate, respiratory rate and arterial blood gases were monitored. The quality of induction and recovery, recovery times and incidence of side-effects were recorded. RESULTS: Induction of anaesthesia was smooth and uneventful, and tracheal intubation was easily performed in all but two goats receiving ketamine. Changes in cardiopulmonary variables and acid-base status were similar with all three induction agents and were within clinically acceptable limits. Mean recovery times (time to recovery of swallowing reflex and to standing) were significantly shorter, and side-effects, e.g. apnoea, regurgitation, hypersalivation and tympany, were less common in goats receiving propofol, compared with the other treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Propofol 3 mg kg(-1) IV is superior to thiopental and ketamine as an induction agent before halothane anaesthesia in goats. It provides uneventful recovery which is more rapid than thiopental or ketamine, so reduces anaesthetic risk.

Anesthesia↗

PubMed1999

Tachycardia induced electrical remodeling of the atria and the autonomic nervous system in goats.

Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so-called electrical remodeling of the atria (ERA) and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 hours, interrupted at 4, 8, 16, and 24 hours for recording of 500 atrial (AA) intervals during sinus rhythm and measurement of the AERP(430ms) at 7.4 +/- 0.6 sites. After 24 hours, pacing was stopped and the electrophysiological study and recording of the AA intervals was repeated at 4, 8, 16, and 24 hours after cessation of pacing. Time- and frequency-domain parameters were computed from each 500 AA interval recording. After 24 hours of rapid pacing the AERP had shortened significantly (147 +/- 5.6 to 102+/- 6.4 ms, P < 0.0001). No significant changes in HRV and dispersion of refractoriness (AAERP) (47 +/- 7.1 to 44 +/- 4.2 ms) were observed. After cessation of pacing, the AERP prolonged again (102 +/-6.4 to 135+/-8.8 ms, P < 0.0001) and was paralleled by a significant increase in AAERP (44 +/- 4.2 to 63+/- 7.1 ms, P = 0.01). Furthermore, HRV increased significantly. At each time point an inverse relation between the logarithmically transformed vagal parameter HF (InHF) and AERP was observed. We calculated the mean InHF for each goat using all time points and used the median value to divide the 12 goats into high and low vagal tone groups. We compared the degree of ERA and recovery from ERA for both groups. The AERP shortened 47.4 +/- 6.5 versus 43.0+/-5.0 ms (NS) for goats with high and low vagal tone, respectively. During recovery from ERA the AERP lengthened 23.6 +/- 4.0 versus 42.5 +/- 1.7 ms (P = 0.001) for goats with high and low vagal tone, respectively. Multivariate regression analysis indicated a short AERP as the single independent determinant of the inducibility of AF during ERA and recovery from ERA (P < 0.0001). During recovery from ERA, the AERP prolonged and vagal tone and AAERP increased. A high vagal tone during recovery from ERA was associated with a short AERP and an attenuated recovery of ERA.

Animals↗

PubMed1987

Pharmacokinetics and metabolism of metioprim in pigs and goats.

The pharmacokinetics and metabolism of metioprim (MTP) have been studied after intravenous administration of a single dose of 5 mg/kg b.wt. to pigs (n = 4) and 10 mg/kg b.wt. to goats (n = 5). Kinetic parameters were calculated using a two-compartment open model. The elimination half-life was much shorter in goats (23 +/- 4 min.) than in pigs (169 +/- 17 min.). The apparent volume of distribution exceeded 1.0 1/kg b.wt. in both species indicating accumulation in tissues. Pigs excreted the major part of the dose (86 +/- 9%) in urine and only a small part (9 +/- 3%) in faeces, while the goats excreted almost equal amounts in urine (55 +/- 5%) and faeces (38 +/- 4%). Metabolism played the major role in elimination of MTP. Of the 80% of the dose excreted in urine within 24 hrs in pigs unchanged MTP made up 8%, metioprim sulfoxide 64% and O-desmethyl-MTP 8%. Metioprim sulfoxide was also the major metabolite in goats, but in this species another demethylated metabolite--metioprim sulfonic acid--was formed. Goats excreted 49 +/- 7% of the dose in urine within 24 hrs of which unchanged MTP made up less than 1%, while metioprim sulfoxide accounted for about 35% and metioprim sulfonic acid for approximately 14%. Metabolites isolated from urine were identified by NMR-spectroscopy combined with EI, FAB or 252Cf plasma desorption mass spectrometry.

Animals↗

PubMed1990

Sensitivity of goats to a light pulse during the night as assessed by suppression of melatonin concentrations in the plasma.

This study investigates the ability of a 1 h light pulse of different intensities at night to suppress plasma melatonin in goats. Six female Saanen dairy goats, about 2 yr old, were housed in a light-tight shed. The goats were habituated for 1 wk to an 8L:16D photoperiod (40.70 +/- 4.16 microW/cm2; 137 +/- 14 lux), lights on 0800 h. A 1 h light pulse, of different intensity on each occasion, was given from 1900 to 2000 h. Light intensity was measured by using a lux meter (mean of 36 measurements at goat's eye level). Five different light intensities were given during December in the order 4.22 +/- 0.62 microW/cm2 (14.2 +/- 2.1 lux), 0.68 +/- 0.09 microW/cm2 (2.3 +/- 0.3 lux), 0.26 +/- 0.004 microW/cm2 (0.87 +/- 0.14 lux), darkness, 40.70 +/- 4.16 microW/cm2 (137 +/- 14 lux), with 1-3 d between treatments. The goats were bled hourly from 1500 to 1900 h and every 15 min from 1900 to 2100 h, and a last bleed occurred at 2200 h. Dark-phase samples were taken in dim red light (less than 0.03 microW/cm2; 0.1 lux). Plasma was assayed for melatonin by radioimmunoassay. Suppression of melatonin concentrations increased as light intensity increased as follows: Darkness, 0%; 0.26 +/- 0.004 microW/cm2; 0%; 0.68 +/- 0.09 microW/cm2; 43.1%; 4.22 +/- 0.62 microW/cm2, 71.1%; 40.70 +/- 4.16 microW/cm2, 81.2%. Suppression was significant (P less than 0.05) at light intensities greater than 0.68 microW/cm2, 2.3 lux. A hyperbolic relationship existed between percent suppression and light intensities.

Analysis of Variance↗

PubMed1985

Effects of a synthetic vasopressin analogue (desmopressin) in pregnant, lactating and anoestral goats.

The effects of the long-acting synthetic vasopressin analogue desmopressin (dose 2 X 2 micrograms day-1 for two days) were investigated in pregnant, lactating and anoestral goats. Urine flow fell and urine osmolality increased in all experiments. However, pregnant goats continued to drink the same volumes of water each day with the result that the ratio of water intake/urine output increased markedly and the plasma osmolality fell. The results support the hypothesis that the regulation of water intake is changed during pregnancy and that pregnant goats have a lowered sensitivity to signals that normally inhibit water consumption. In lactating goats, milk secretion was not affected by desmopressin. The animals did not drink enough to compensate for the water losses in milk and urine, but more than was needed to cover the water losses in the urine. The plasma osmolality decreased slightly. It appears as if the mechanisms involved in the control of water balance are not sufficiently adapted to take water losses via the milk into account, if the animals are subjected to challenges. In anoestral animals, the water balance was maintained during desmopressin injections. The renal sodium excretion did not change, but the renal potassium excretion decreased in pregnant and lactating goats in response to desmopressin.

Anestrus↗

PubMed1987

Renal and hormonal responses to atrial natriuretic peptide infusions in goats on high and low sodium intake.

Synthetic atrial natriuretic peptide (ANP) was infused intravenously (1 microgram min-1; 60 min) in five goats during two series of experiments. For at least 4 weeks before the ANP infusions the goats received either no salt supplementation (= low sodium diet), or were given 16 g NaCl mixed with the food each day (Na = 274 mmol day-1; high sodium intake). The goats were changed between the treatments at random. ANP infusions caused diuresis, natriuresis and haemoconcentration during both diets. The urinary Na excretion increased about four-fold during the high sodium intake, and about 10 times during the low sodium intake. The urinary K excretion increased significantly during the low sodium diet, but decreased slightly during the high sodium intake. During both diets the K excretion became significantly lowered after the infusions. The mean glomerular filtration rate (GFR) was generally lower during the low sodium diet, but increased significantly during ANP infusions on both diets. The GFR returned to baseline immediately after the infusions, in contrast to urine flow and urinary Na excretion. Renal free water clearance increased slightly at the end of the infusion during the low sodium diet, but did not change during the high salt diet. Plasma renin activity (PRA) and plasma aldosterone concentration fell during ANP infusions in goats on the low sodium intake, but did not change significantly during the high sodium diet. These results indicate that the diuresis and natriuresis observed during intravenous ANP infusions in goats are mainly due to increased GFR.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗