The effect of GnRH or oestradiol injected at pro-oestrus on luteal function and follicular dynamics of the subsequent oestrous cycle in non-lactating cycling Holstein cows

Oestrous synchronization involves synchronization of ovarian follicular turnover, new wave emergence, and finally induction of ovulation. The final step can be synchronized by the parenteral administration of either GnRH or oestradiol benzoate. This study investigated corpus luteum and follicular emergence after ovulation had been induced by the administration of either GnRH or oestradiol benzoate. The injection of oestradiol benzoate may have delayed the emergence of the first follicular wave subsequent to the induced ovulation; administration of oestradiol benzoate or GnRH lowered the progesterone rise so that the maximum dioestrous concentration of progesterone on Day 9 was lower when cows were treated during pro-oestrus compared to the spontaneously ovulating controls. One implication of findings from the present study is that induction of ovulation with either oestradiol benzoate or GnRH, administered 24 or 36 h after withdrawal of the CIDR device, respectively, may lower fertility. Future studies must identify the timing of administration relative to the time of CIDR device withdrawal and the optimum concentration of oestradiol benzoate or GnRH that would not have untoward effects on the development of the corpus lutea, particularly within the first week of dioestrus.     

Effects of the gill monogenean Zeuxapta seriolae (Meserve, 1938) and treatment with hydrogen peroxide on pathophysiology of kingfish, Seriola lalandi Valenciennes, 1833

Infections by the gill fluke Zeuxapta seriolae are a serious concern for sea cage aquaculture of kingfish, Seriola lalandi. The present study aimed to determine the pathophysiological effects of a progressive infection with Z. seriolae and the effects of treatment with hydrogen peroxide. For the progression of infection study, infected fish were taken from a sea cage farm, treated to remove parasites and then infected by cohabitation with heavily infected fish. Samples were taken at 2-week intervals for 8 weeks. Infection intensity peaked at 4 weeks post-infection (mean intensity 565.9) and the number of mature worms (2 mm fixed length or larger) peaked at 6 weeks post-infection. Attachment of Z. seriolae appeared to cause little localized pathology; however, the occurrence of hyperplastic lamellae increased as the infection progressed. Haemoglobin concentrations were negatively correlated with Z. seriolae intensity and were lower than controls at 4 weeks (35.8% decrease) and 6 weeks (57.4% decrease) post-infection. Blood lactate concentration and plasma osmolality increased throughout the course of infection. For the effect of treatment experiment, groups of infected and non-infected fish were sampled either before or after treatment with hydrogen peroxide. Treated fish from both infected and uninfected groups had increased plasma lactate, osmolality and pH compared with pre-treatment groups. Treatment with hydrogen peroxide appeared to have acute effects on fish health but the magnitude (e.g. lactate, osmolality) and extent of the effects (e.g. haemoglobin) was much less than that caused by chronic infection with Z. seriolae.     

The spread of Corynebacterium pseudotuberculosis infection to unvaccinated and vaccinated sheep

SUMMARY The decrease in the prevalence of Corynebacterium pseudotuberculosis after two generations of vaccination against the disease it causes, was used to estimate the rate of control of caseous lymphadenitis (CLA). Three groups of 150 sheep, of which 50 in each group were artificially infected with C pseudotuberculosis and 100 in each group were uninfected sheep, were run separately for 40 months and shorn 5 times to promote the spread of CLA. One lot of 50 infected sheep and 2 lots of 100 uninfected sheep were vaccinated against CLA. The rate of spread of CLA was recorded. Sheep vaccinated against CLA and naturally exposed to infection had a 74% lower infection rate than unvaccinated sheep. Sheep vaccinated against CLA and exposed to only vaccinated infected sheep had a 97% lower infection rate. Unvaccinated sheep had a 76% infection rate, with 77% of the transmission occurring at the 4th and 5th shearings, without any discharging CLA abscesses being observed. This study supports the view that in Australian wool producing flocks, CLA spreads mainly from sheep with discharging lung abscesses to sheep with shearing cuts. Vaccinated sheep infected with CLA have 96% fewer lung abscesses compared with unvaccinated infected sheep and are therefore less likely to spread this disease to other sheep .     

Bovine platelets retain functional activity in the presence of penicillin G.

It has been reported that antibiotics of the penicillin family impair the functional response of human, canine and lapine platelets to a broad range of agonists. In contrast, we have shown that the bovine platelet retained full functional responses to stimulation by adenosine diphosphate (ADP) or platelet activating factor (PAF) following administration of penicillin G to clinically normal cattle at 20,000 IU/kg for three days. The aggregation response to collagen was transiently reduced to approximately 50% of pretreatment values, but only while the drug was detectable in the circulation. When penicillin was added to platelet rich plasma suspensions, ADP-induced aggregation was similar to that of the control untreated platelets, while the PAF-induced aggregation response was reduced by not more than 25%. Only collagen-induced aggregation exhibited a modest dose-dependent inhibitory response in the presence of penicillin. It is postulated that the relative insensitivity of the bovine platelet to penicillin may be related to differences in postreceptor biochemical events compared to the human platelet.     

Morphologic, immunohistochemical, and molecular characterization of hepatosplenic T-cell lymphoma in a dog

A 13-year-old neutered male Jack Russell Terrier (Parson Russell Terrier) was presented to the Texas Veterinary Medical Center with a history of lethargy, depression, vomiting, and fever. The dog had mildly regenerative anemia, severe thrombocytopenia and low antithrombin activity. Marked splenomegaly was found on physical examination and imaging studies, and malignant round cell neoplasia and marked extramedullary hematopoiesis were diagnosed on aspirates of the spleen. The dog underwent exploratory laporatomy and splenectomy. Because of a rapid decline in clinical condition postsurgery, the dog was euthanized. Splenic and hepatic biopsies were submitted for histopathologic evaluation. A neoplastic population of round cells was found throughout the splenic parenchyma and within hepatic sinusoids. The neoplastic cells stained strongly positive for CD3 (T-cell marker) and were negative for CD79a (B-cell marker) and lysozyme (histiocytic marker). A diagnosis of T-cell lymphoma was confirmed by assessment of T-cell clonality using canine-specific polymerase chain reaction-based techniques. Although expression of the gammadelta T-cell receptor was not evaluated, this case shares many similarities with a rare syndrome in humans known as hepatosplenic gammadelta T-cell lymphoma.     

New infection with Corynebacterium pseudotuberculosis reduces wool production

SUMMARY The effect of natural Corynebacterium pseudotuberculosis infection on wool production and quality in sheep was examined in light of evidence that artificial C pseudotuberculosis infection causes wool production loss. A toxin ELISA was used to identify sheep that had been infected with C pseudo tuberculosis. Greasy and clean fleece weights and fibre diameter were compared in infected and uninfected sheep. C pseudotuberculosis infection caused a 3.8 to 4.8% decrease in greasy wool production and a 4.1 to 6.6% decrease in clean wool production. C pseudotuberculosis infection did not affect fibre diameter. The effects of caseous lymphadenitis (the disease caused by C pseudotuberculosis infection) cause an annual loss of about $17 million in wool production to the Australian wool industry.