OC9Effect of Melatonin Implants in Guirra Ewes

In extensive systems, beef cows should be continuously with their calves to optimise pasture use but this practice can lengthen post-partum interval (PPI). A study was conducted to determine the influence of suckling frequency on Parda de Montaña cow-calf performance when cows are fed 70% energy requirements during lactation (outdoor winter conditions simulation). Thirty-six autumn-calving cows with similar body condition at calving (2.57) were assigned to three suckling systems [ ad libitum (AL), twice (2D) or once daily (1D) for 30 min]. Blood samples were collected twice a week to analyse progesterone concentrations by RIA. Cows lost similar weight until start of mating period (day 52 post-partum; −0.583, –0.513, –0.520 kg/day in AL, 2D and 1D). Standard milk yield was higher in AL than the rest (8.9, 6.2, 7.0 kg; p < 0.05), which was reflected on greater calf gain (0.895, 0.752, 0.676 kg/day; p < 0.05) and larger cow weight loss within 90 days post-partum in this treatment (–0.345, –0.188, –0.083 kg/day; p < 0.05). Suckling system did not affect either PPI (69.6, 89.1, 65.5 days) or cows cycling within 90 days post-partum (55, 46, 58%), which may compromise the target calving interval. In Parda de Montaña breed fed moderately pre-calving and undernourished during lactation, restricted suckling did not favour ovarian activity resumption, but post-partum subnutrition delayed about 40 days PPI observed in similar body condition at calving and calf management (Sanz et al., 2003; Anim Reprod Sci 79: 57–69)     

Epidemiological and economic models for spread and control of citrus tristeza virus disease

Citrus tristeza virus (CTV) causes a most destructive citrus disease in many parts of the world, and indications of natural spread were found in Israel in 1970. The strategy for controlling the disease in Israel is based on the eradication of virus-infected trees, detected by test plants or immunological methods. Mathematical models for CTV infection and spread were developed and used to assess the cost-effectiveness of the eradication policy. It was concluded that the discovery-eradication program is economically justified and superior to allowing the disease to progress unchecked.     

Expression and Activity of Steroid Sulphatase in the Boar Testis

Oestrogens are essential for male fertility targeting the testicular-epididymal compartment. However, the underlying mechanisms are only vaguely known and species specificities must be considered. The boar has a remarkably high testicular-oestrogen output, with the biologically inactive oestrone-sulphate being the major oestrogen occurring in the testicular vein. In the boar testis and epididymis, activity of steroid sulphatase (StS) and oestrogen sulphotransferase has been demonstrated. Thus apart from their synthesis in Leydig cells, provision of biologically active free oestrone seems also to depend on the activity and localization of these enzymes. Our aim was to establish expression patterns and activity of StS in boar testis. Testes were randomly collected from healthy boars and allotted to five age groups, five animals in each, aged 50, 100, 150, 200 and 250 days. Three extra boars aged over 250 days were castrated to obtain fresh tissue for enzyme activity tests. Immunohistochemistry detected StS only in the cytoplasm of Leydig cells and – except for day-50 group in which 65.1 ± 4.9% (X ± SD) of the cells were positive – expression was constant with virtually all the cells staining positive. RT-PCR and in situ hybridization confirmed expression and localization of StS mRNA. The V _max and K _m value (X ± SD) for StS was 24.05 ± 0.3 fmol/s/μg protein and 2.15 ± 0.12 μ m . These data suggest that StS within the Leydig cells of the boar is involved in modulation of testicular oestrogen bioavailability and that the site of sulpho-conjugation is not the testis but a different compartment of the testes–epididymidis complex.     

A canine distemper virus seroprevalence study of dogs on three islands in the Torres Strait region,Australia

Canine distemper virus (CDV) can cause mortality in domestic dogs, which is easily prevented by the consistent application of vaccination protocols. The aim of this study was to determine if the dog populations of three strategically located islands in the Torres Strait of Australia, adjacent to Papua New Guinea, are infected by CDV. Eighty-four serum samples were collected from 70 dogs resident on Saibai, Dauan and Boigu Islands during 2017–2018. Sera were tested for CDV antibodies by a virus neutralization test (VNT). Overall, 7 (8.3%) sera from 6 (8.6%) dogs resident on all three islands were test positive. VNT titres ranged from 20 to >1280. Male adult dogs were more commonly seropositive than female and juvenile dogs. Considering the origin and age of test positive dogs, and veterinary visits to these islands, it was concluded that there is evidence of exposure to a field strain of CDV – rather than previous vaccination – in 4 of the 70 dogs (5.7%) tested in this study. Given the strategic location of these islands in a zone of high biosecurity risk, ongoing surveillance of pathogens such as CDV could inform on potential disease spread pathways in this region. In addition, the presence of high serological titres in the apparent absence of clinical disease requires further investigation.     

Disposition of ampicillin trihydrate in plasma,uterine tissue,lochial fluid,and milk of postpartum dairy cattle

The objective of this study was to determine the disposition of ampicillin in plasma, uterine tissue, lochial fluid, and milk of postpartum dairy cattle. Ampicillin trihydrate was administered by intramuscular (i.m.) injection at a dose of 11 mg/kg of body weight every 24 h (n = 6, total of 3 doses) or every 12 h (n = 6, total of 5 doses) for 3 days. Concentrations of ampicillin were measured in plasma, uterine tissue, lochial fluid, and milk using HPLC with ultraviolet absorption. Quantifiable ampicillin concentrations were found in plasma, milk, and lochial fluid of all cattle within 30 min, 4 h, and 4 h of administration of ampicillin trihydrate, respectively. There was no significant effect of dosing interval (every 12 vs. every 24 h) and no significant interactions between dosing interval and sampling site on the pharmacokinetic variable measured or calculated. Median peak ampicillin concentration at steady‐state was significantly higher in lochial fluid (5.27 μg/mL after q 24 h dosing) than other body fluids or tissues and significantly higher in plasma (3.11 μg/mL) compared to milk (0.49 μg/mL) or endometrial tissue (1.55 μg/mL). Ampicillin trihydrate administered once daily by the i.m. route at the label dose of 11 mg/kg of body weight achieves therapeutic concentrations in the milk, lochial fluid, and endometrial tissue of healthy postpartum dairy cattle.