A.M. Padula

Reproductive responses of early postpartum dairy cattle to continuous treatment with a GnRH agonist (deslorelin) for 28 days to delay the resumption of ovulation

An experiment was conducted to investigate the potential of chronic delivery of a potent GnRH agonist (deslorelin) via subcutaneous implants to delay the resumption of ovulatory cycles in postpartum dairy cattle. Cows received either a single deslorelin implant (n=40; DES) within 7 days of calving or were untreated (n=24; CON). Blood samples were collected thrice weekly during the period the implants were in place. Plasma concentrations of progesterone (P4) and 17beta-oestradiol (E2) were measured along with selected serum metabolites. Implants were removed after 28 days and cattle monitored daily for behavioral oestrus. Serial weekly blood samples were collected to detect the occurrence of ovulation. Cows were artificially inseminated as they were detected in oestrus from 30 days after implant removal. Pregnancy status was subsequently determined by manual palpation of uterine contents at strategic intervals. Insertion of implants induced ovulation in 3/40 cows as determined by a rise in progesterone 7 days later. Deslorelin implants delayed the onset of ovulatory cycles compared with untreated herdmates (mean 43.4+/-4.2 versus 57.3+/-1.6 days postpartum; P<0.001). A noticeable delay of at least 12 days was observed between implant removal and the first animals ovulating. Mean plasma E2 concentrations during the period the implants were in place were similar for DES and CON cows that experienced a prolonged spontaneous postpartum anoestrus (low P4 >60 days), although both groups had concentrations only 20% of CON cows that had ovulated prior to 30 days postpartum. The patterns of recovery following implant removal were highly variable. A number of DES cows showed a low and transient rise in plasma progesterone around 21 days after implant removal. Some cows displayed oestrus but did not appear to form a fully functional corpus luteum with this phenomenon being more prevalent among DES cows (7 of 37 versus 1 of 21; P<0.05). Overall, significantly more DES cows were detected in oestrus without ovulating compared to CON cows. Final pregnancy rates did not differ between DES and CON groups. The mean time to conception for DES cows was longer (21.2+/-5.6 versus 41.1+/-7.4 days, CON versus DES; P<0.01). This difference was not present if the time from first ovulation to conception was compared (50.5+/-5.3 versus 43.5+/-9.3 days, CON versus DES; P>0.05). Deslorelin implants provided a reliable method of inducing anoestrus when treatment was initiated prior to 3 days postpartum. A variable pattern of recovery was observed which delayed conception but did not ultimately reduce the final proportion pregnant at the completion of mating. The study demonstrates the potential of GnRH agonists to control postpartum reproductive function to manipulate the fertility of dairy cows.

Restoration of LH output and 17β-oestradiol responsiveness in acutely ovariectomised holstein dairy cows pre-treated with a GnRH agonist (deslorelin) for 10 days

The objectives of the study were firstly to identify the role of the ovary in maintaining plasma luteinising hormone (LH) concentrations in cows treated with an implant of a potent GnRH agonist (deslorelin), and secondly to characterise the changes in LH following ovariectomy (OVX) in the same animals. Oestrus was synchronised in mature Holstein dairy cows and deslorelin implants were inserted 17 days later into two-third of the cows. A further 10 days later (day 0) all cows had bilateral OVX performed. A control group (CON; n=4) received no treatment and had blood samples collected at 15-min intervals for 8h on the day prior to OVX (day -1) and similarly on days 4 and 10. One group (DES_IN; n=4) had implants in place for the duration of the study while another group had implants removed (DES_OUT; n=4) at the time of OVX. DES_IN cows were sampled hourly at each sampling session (days -1, +4 and +10), whereas DES_OUT cows were sampled similarly to CON except on day -1 when hourly samples were collected. Predictable post-operative increases in mean LH (0.61 ng/ml versus 1.79 ng/ml; P<0.01) and LH pulse amplitude (0.66 ng/ml versus 1.56 ng/ml; day -1 versus day +10; P<0.01) occurred after CON cows were ovariectomised. Smoothed LH means showed a delayed effect of time compared to arithmetic means. Pulse frequency was unchanged following OVX in CON cows. A comparison of all cows that had been treated with deslorelin from day -1 showed a significant elevation of smoothed mean LH compared to untreated cows (0.80 ng/ml versus 0.34 ng/ml; DES_IN and DES_OUT versus CON; P<0.05). DES_IN cows had a 54% reduction in mean LH from day -1 to +4 following OVX (1.05 ng/ml versus 0.48 ng/ml; P<0.01) indicating the probable involvement of the ovary in the maintenance of elevated basal LH. No further reduction was detected by day +10. The LH response to an intramuscular (IM) injection of 500 microg 17beta-oestradiol (E2) on day +11 varied significantly between treatment groups (P<0.01). CON cows showed a typical LH surge, reaching maximum concentrations (10.3 ng/ml) at 17.3h post-injection. Even though low amplitude LH pulsatility had been restored in DES_OUT cows by day +4, there was an inconsistent response to E2 on day +12; one cow had an apparently normal surge yet, others showed only attenuated responses. Pulse amplitude in DES_OUT cows was lower at days +4 and +10 compared to CON (P<0.05). DES_IN cows did not produce any surge after E2. Mean LH prior to OVX (day -1) remained unchanged following the 500 microg oestradiol injection (0.38 ng/ml versus 0.45 ng/ml pre-E2 versus post-E2 compared to 1.05 ng/ml pre-OVX). The results of this experiment implicated ovarian involvement in maintaining elevated basal LH output in cows that were chronically treated with a GnRH agonist. Individual cows varied in their LH surge response to exogenous E2 given 12 days after implant removal, even though LH pulse amplitude and frequency had been restored.

Fatal presumed tiger snake (Notechis scutatus) envenomation in a cat with measurement of venom and antivenom concentration.

A fatal outcome of a presumed tiger snake (Notechis scutatus) envenomation in a cat is described. Detectable venom components and antivenom concentrations in serum from clotted and centrifuged whole blood and urine were measured using a sensitive and specific ELISA. The cat presented in a paralysed state with a markedly elevated serum CK but with normal clotting times. The cat was treated with intravenous fluids and received two vials of equine whole IgG bivalent (tiger and brown snake) antivenom. Despite treatment the cats condition did not improve and it died 36 h post-presentation. Serum concentration of detectable tiger snake venom components at initial presentation was 311 ng/mL and urine 832 ng/mL, this declined to non-detectable levels in serum 15-min after intravenous antivenom. Urine concentration of detectable tiger snake venom components declined to 22 ng/mL at post-mortem. Measurement of equine anti-tiger snake venom specific antibody demonstrated a concentration of 7.2 Units/mL in serum at post-mortem which had declined from an initial high of 13 Units/mL at 15-min post-antivenom. The ELISA data demonstrated the complete clearance of detectable venom components from serum with no recurrence in the post-mortem samples. Antivenom concentrations in serum at initial presentation were at least 100-fold higher than theoretically required to neutralise the circulating concentrations of venom. Despite the fatal outcome in this case it was concluded that this was unlikely that is was due to insufficient antivenom.

Absorbable deslorelin implants (Ovuplant) prolong postpartum anestrus in early ovulating dairy cows.

Two experiments were conducted to investigate the use of a bioabsorbable implant of the GnRH agonist deslorelin to temporarily delay the resumption of postpartum ovulatory cycles in Holstein cows. In Experiment 1, recently calved cows were paired and received either a single implant (Ovuplant); Peptech Animal Health, Sydney, NSW, Australia) within 48 h of parturition (OVP; n=17), or remained as untreated controls (CON; n=17). Blood samples were collected for plasma progesterone assay three times weekly for 6 weeks to profile the pattern of resumption of ovulatory cycles. In Experiment 2, there were 15 CON and 15 OVP cows initially treated as for Experiment 1 as well as 15 OVP+SYNCH cows. Each cow in the CON and OVP+SYNCH groups received a progesterone vaginal insert (CIDR); Genetics Australia, Bacchus Marsh, Vic., Australia) for 7 days at 23 days postpartum (23 dpp) to synchronise estrus in cycling animals or to induce an ovulation with estrus in anestrus animals. Blood samples were collected weekly until removal of the CIDR insert, and then twice weekly until 56 dpp to monitor plasma P4 for retrospective determination of ovulation. Milk yield was monitored by twice daily electronic volume measurements and milk composition with once weekly milk composition analysis. In Experiment 1, CON cows began ovulating from 9 dpp; 15 of 17 had ovulated by the end of blood sampling at 42 dpp. None of the OVP cows ovulated until at least 24 dpp, and only 6 of 17 had ovulated by 42 dpp. The average day of first ovulation was extended from 22.4+/-2.7 dpp to 39.3+/-2.7 dpp (P<0.05). In Experiment 2, ovulation had occurred in 8 of 15 CON cows at the time of CIDR insertion (23 dpp), 0 of 15 OVP cows and 1 of 15 OVP+SYNCH cows. By 40 dpp (or 10 days following removal of the CIDR insert) every CON cow (15/15) had ovulated, but only 2 of 15 OVP+SYNCH cows and 1 of 15 OVP cows. None of these effects of treatment was associated with any changes in milk yield or composition in either experiment. In conclusion, inserting a bioabsorbable implant of deslorelin within 48 postpartum extended the interval to first ovulation to at least 24 dpp in 46 of 47 cows. Recovery periods were highly variable. This variability was not reduced by using a form of intravaginal progesterone supplementation that did produce a synchronised estrus with ovulation in anestrus animals that had not been treated with deslorelin.

Temporary suppression of pulsatile LH release following a single injection of a GnRH agonist (deslorelin) in ovariectomised Holstein dairy cows.

The objective of the experiment was to investigate the potential for using a single injection of the GnRH agonist [D-Trp(6), Pro(9)-des-Gly(10)-NH(2)] GnRH-ethylamide (deslorelin) to suppress LH secretion in ovariectomised Holstein cows. Each dose of 10, 100 and 1000 microg deslorelin was injected intravenously into each of four ovariectomised cows on day 0. Blood samples were collected hourly on day 0 to profile the induced LH release. Frequent serial blood samples were collected at 10min intervals over 4h on days -3, -1, +2, +4 and +6. The injection of deslorelin induced a surge-like release of LH that begun within 1h in all cows. There was no difference between deslorelin doses in terms of maximum LH concentration, area under the LH curve (AUC) or log(10)(AUC). The average interval from injection to maximum LH concentration was longer for cows receiving 1000 microg than in those receiving 10 microg (3.5 versus 1.5h; P<0.01), though no different to 100 microg (2.8h; P>0.1). This relationship was described by a logarithmic function of deslorelin dose in micrograms (R(2)=73.3%, P<0.01). Pre-treatment smoothed mean LH concentration was significantly correlated with peak LH concentration of the induced surge: max_LH=5.37+9.57 x pre-amplitude (R(2)=33.2%, P=0.05). Similarly, LH pulse amplitude pre-deslorelin was also correlated with peak LH of the induced surge max_LH=0.07+12.9 x pre-amplitude (R(2)=53.7%, P=0.07). Pulsatile release of LH was suppressed only with the 1000 microg dose on day +2. Suppression was characterised by a reduction in mean LH, smoothed mean LH and LH pulse amplitude. By day +4, LH parameters were no different to pre-treatment ones. Pulse frequency was not affected by the treatment, although a small non-significant reduction at day +2 for 1000 microg dose was observed (3.9 versus 2.8, P=0.14). In conclusion, temporary suppression of LH output for at least 48h occurred following a single intravenous injection of 1000 microg of deslorelin, even though there were similar peak LH concentrations were for the three doses.

Eastern brown snake (Pseudonaja textilis) envenomation in dogs and cats: Clinical signs, coagulation changes, brown snake venom antigen levels and treatment with a novel caprylic acid fractionated bivalent whole IgG equine antivenom

&NA; This report describes the diagnosis and treatment of 16 confirmed cases of snakebite from the Australian eastern brown snake (Pseudonaja textilis) in dogs and cats. The clinical signs, brown snake venom antigen concentrations, coagulation parameters, and treatment outcomes following administration of an experimental caprylic acid fractionated bivalent whole IgG antivenom are documented. A brown snake venom antigen specific sandwich ELISA was used to retrospectively quantify venom levels in serum and urine. The characteristic clinical signs of envenomation in all cases were neurotoxicity to a variable extent and coagulation disturbances. The median serum venom concentration at presentation was 122 ng/mL and ranged from 1.9 to 3607 ng/mL. The median urine venom concentration at presentation was 55 ng/mL and ranged from 3.3 to 2604 ng/mL. Mechanical ventilation was used to successfully support respiration in three severely paralysed cases for 1–30 h. In four cases where serum samples were available post‐antivenom treatment, venom was no longer detectable. Coagulation parameters measured on citrated plasma samples collected prior to antivenom from each case were abnormally prolonged to variable degrees in all cases. Three cases (2 dogs; 1 cat) were euthanized within four hours of presentation for either cost based reasons (2) or poor prognosis (1). One dog developed massive and potentially fatal pulmonary haemorrhage and was euthanazed. In vitro testing of the venom procoagulant neutralising efficacy of the experimental antivenom demonstrated it was 9.6–72 times more effective when compared to two other commercial veterinary antivenom products. This is the first detailed report of a case series of P. textilis envenomation in dogs and cats. The envenomation syndrome in dogs and cats differed to that reported humans, dominated by neurotoxicity and coagulopathy; unlike in humans, where coagulopathy is of primary clinical significance. HighlightsCase series of 16 brown snake envenomation (Pseudonaja textilis) in dogs and cats.Neurotoxicity is a clinical feature in dogs and cats in contrast to humans.Mechanical ventilation required to support respiration in some severe cases.Coagulation changes present in all cases.Potentially fatal haemoptysis observed in one case leading to euthanasia.

Severe acute pulmonary haemorrhage and haemoptysis in ten dogs following eastern brown snake (Pseudonaja textilis) envenomation: Clinical signs, treatment and outcomes

This report describes a series of ten cases of fulminant pulmonary haemorrhage in dogs following envenomation by the eastern brown snake (Pseudonaja textilis) in south eastern Queensland, Australia. All cases were presented for veterinary treatment during 2011-2018 at a specialist veterinary emergency centre. Each case received prompt antivenom treatment and supportive care. Pulmonary haemorrhage was diagnosed based on clinical examination; overt haemoptysis; thoracic radiographic demonstration of a diffuse alveolar pattern; and, the presence of venom induced consumptive coagulopathy. The median elapsed time from hospital admission to onset of haemoptysis was 2 h (range 0-18 h). In 80% (8/10) of cases endotracheal intubation was required, whilst 20% (2/10) were successfully treated with mask oxygen supplementation alone, and 40% (4/10) received mechanical ventilation; but only 25% (1/4) of these survived to hospital discharge. Fresh frozen canine plasma was administered to 70% (7/10) of cases and 43% (3/7) of these survived. Of the total number of cases presented for treatment, 30% (3/10) survived to hospital discharge, 60% (6/10) were euthanised due to poor prognosis and 10% (1/10) died from cardiac arrest. Initial serum brown snake venom antigen levels were retrospectively measured from frozen serum samples by venom specific sandwich ELISA in two dogs at 154 ng/mL (survived) and 3607 ng/mL (euthanised); no free venom was detected post-antivenom. Dogs that survived were discharged from hospital without apparent complications. Pulmonary haemorrhage is an uncommon event following envenomation by P. textilis in dogs and has not been described in similarly envenomed humans. This case series highlights the potential for fulminant and fatal pulmonary haemorrhage in dogs following eastern brown snake envenomation.

Severe haemolysis and spherocytosis in a dog envenomed by a red-bellied black snake (Pseudechis porphyriacus) and successful treatment with a bivalent whole equine IgG antivenom and blood transfusion

This case report describes a dog envenomed by a red-bellied black snake (RBBS; Pseudechis porphriacus) that experienced severe and life-threatening haemolysis. The dog presented with hypersalivation, facial swelling, mildly prolonged activated clotting time and the absence of neurological deficits. Envenomation was confirmed by positive identification of the snake and retrospective measurement of RBBS specific venom antigen (24 ng/mL) in serum. The dog was initially hospitalised, treated with intravenous fluids and one vial of tiger-brown snake antivenom which is recommended for RBBS envenomation in Australia. However, after 3.5 d the dogs PCV had declined to 15% and the dog was dull and tachycardic. A second vial of tiger-brown antivenom followed by a packed red blood cell transfusion was administered. A rapid clinical improvement within 12 h was observed. No free RBBS venom was detected in serum at any time point after the first vial of antivenom. Longitudinal haematology and biochemical profiling was performed to 62 d post-envenomation and revealed a gradual recovery in the haematocrit to normal reference range. Spherocyte numbers on blood smear were highest at 5 d post-envenomation and gradually declined to undetectable after 62 d. This case highlights the potential for unpredictable, severe and life-threatening anaemia resulting from RBBS envenomation in dogs.