CONGENITAL BOVINE EPIZOOTIC ARTHROGRYPOSIS AND HYDRANENCEPHALY

SUMMARY Epizootics of congenital neurological defects in calves have been recorded at various intervals in south eastern New South Wales for over 40 years. In 1974 a particularly severe outbreak occurred. Field observations of the clinical entities, their time of appearance, distribution and incidence were recorded in an attempt to determine an epidemiological pattern. The neurological entities observed occupied different time spans in the opizootic, the order of appearance being polioencephalomyelltis, arthrogryposis, hydranencephaly and micrencephaly. The probable period of infection correlated well with the likely presence of Culiciodes brevitarsus in the epizootic area and the distribution and incidence of neurologic cases likewise correlated well with the expected geographical and climatic distribution of C. brevitarsus in this period. The probable association of Akabane virus infection and the outbreak of stillbirths and abortions which preceded the neurologic entities is discussed.     

Articular/epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: Influences of growth of the foal and prenatal copper supplementation of the dam

AIMS: To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age.

METHODS: Thirty-three Thoroughbred foals, born in two consecutive years, were weighed every 2 weeks from birth. The dams had been supplemented with parenteral Cu or saline during late gestation, and the supplementation regimens were different in each year. Foals had liver biopsies harvested at birth for determination of Cu concentration. Pasture samples were collected every 4–8 weeks for analysis of concentration of Cu and zinc (Zn). At 160 days of age, articular cartilage of long bones was examined. Gross lesions were counted and scored, then sawn and radiographed, and processed for histopathology. Lesions were given radiographic scores and histopathological scores. Maximum scores for each lesion were combined to give a total OC score for each joint and each foal. The fatness of 20 foals (10 each from Years 1 and 2) at 160 days of age was determined chemically.

RESULTS: Supplementation of dams with Cu had no significant effect on the concentration of Cu in the liver of foals at birth, or on the frequency or severity of lesions in articular cartilage at 160 days of age. The Cu and Zn concentrations of pasture were similar in Years 1 and 2, and were lower than current recommendations. All foals in Year 2, and 9/10 foals in Year 1 had irregularities in cartilage that was confirmed histologically to be indicative of OC. The average number of lesions per foal was 4.7 (SD 1.1) and 5.7 (SD 1.1) in Years 1 and 2, respectively. However, the severity of the lesions was considered mild, and no foals showed any clinical evidence of OC while alive. The number of lesions in the tarsocrural (TC) joint and the TC OC score at 160 days were positively associated with average daily weight gain (ADG) in the previous 4 weeks (p=0.005 and p=0.001, respectively). There was no significant effect of sex, fatness, birth-weight, weight at 160 days of age, or year of birth of the foal on the frequency and severity of OC lesions.

CONCLUSIONS: Many of the lesions classified as OC, using classification systems described by other authors, were likely to be normal variations of the process of endochondral ossification. Despite the high frequency of such lesions, they were considered to be of minor significance and none were clinically evident. The distribution of lesions was not typical, and most probably reflected the subtlety of the lesions. These results support the hypothesis that Cu is an over-emphasised factor in the aetiopathogenesis of OC. The relationship between subtle macroscopic lesions and lesions resulting in clinical signs of disease requires further investigation.     

Effect of Artificial Insemination Protocol and Dose of Frozen/Thawed Stallion Semen on Pregnancy Results in Mares

Deep intra‐uterine insemination is commonly accepted as a routine procedure for artificial insemination in horses. The motives and principles of deep insemination are well described, but the equipment used may differ. In this trial, the efficiency of two different insemination pipettes for deep intra‐uterine insemination in the mare was compared with insemination into the uterine body using commercially available frozen–thawed semen of two stallions of proven fertility. These inseminations were performed using two different doses. The semi‐flexible Minitube pipette was compared with a newly designed insemination device with a more flexible telescopic insemination catheter (Ghent device). The semi‐flexible Minitube pipette performed better than the newly designed insemination device with respect to pregnancy outcome (p = 0.008). The superiority of deep horn insemination over uterine body insemination was reflected by the better pregnancy rates obtained after deep insemination using the same low doses (30.6% better pregnancy rates) (p = 0.0123).     

Efficacy of Medroxyprogesterone Acetate in Suppression of Estrus in Cycling Mares

The effects of compounded medroxyprogesterone acetate (MPA) on follicular activity and estrous behavior were evaluated. Eighteen cycling mares were assigned to one of three treatment groups. Mares in the MPA group (n = 6) were injected intramuscularly with 1,600 mg MPA (week 1), then 400 mg weekly for the next 5 weeks. Saline mares (n = 6) were injected intramuscularly weekly for 6 weeks. Altrenogest mares (n = 6) received 10 mL orally daily for 7 weeks. Mares were teased daily for 60 days and categorized as displaying estrous, diestrous, or neutral behavior. Transrectal ultrasound examinations were performed three times weekly, or daily when a 30-mm follicle was identified, until ovulation. Blood samples were harvested weekly for analysis of progesterone concentration and daily from days 14 to 23 for analysis of luteinizing hormone (LH) concentration. Mares treated with saline or MPA showed normal intervals of diestrus and estrus during the study. All altrenogest mares showed behavioral diestrus during treatment. All mares in the saline and MPA groups showed normal follicular development and ovulations. No altrenogest mares ovulated during treatment; four mares returned to estrus and resumed normal follicular development after treatment ceased. Progesterone analyses agreed with transrectal ultrasonographic ovarian activity for all mares. LH levels were lower for altrenogest-treated mares compared with MPA-treated and saline-treated mares during the treatment period. In conclusion, compounded MPA at dose rates and intervals used in this study was not effective in suppression of estrus, follicular development, or LH secretion in mares.     

Effect of testicular tissue lysate on developmental competence of porcine oocytes matured and fertilized in vitro

The objective of the present study was to investigate the effect of testicular tissue lysate (TTL) on developmental competence of germinal vesicle (GV) stage porcine oocytes. Two types of TTL were prepared through repeated freeze–thaw in liquid nitrogen, one from whole testicular tissue (wTTL) and other from either of four different sections of testes, namely just beneath the tunica albuginea (TA), from the transitional area between the seminiferous cord/tubules and the mediastinum testis (TR) and from the intermediate area (parenchymal tissue origin) and CE (cauda epididymis origin). The whole or section‐wise TTL treatments were given for 44 hr during in vitro maturation (IVM). Oocyte maturation was done in either of the two media, namely defined (high‐performance basic medium for porcine oocyte maturation, commercially available) and serum containing (TCM199). After maturation, oocytes were co‐incubated with fresh spermatozoa for 6 hr and then transferred to embryo culture media. Treatment of GV stage oocytes with wTTL (1 mg/ml) increased the cleavage and morula percentage rate (69.23 ± 6.23 and 48.15 ± 6.77, respectively) than that of their control (58.33 ± 8.08 and 32.54 ± 5.53, respectively) in defined media, and in serum‐containing media, cleavage and morula percentage rate were almost equal in both treatment (54.56 ± 7.79 and 34.70 ± 6.78, respectively) and control (59.52 ± 8.21 and 38.52 ± 6.54, respectively). However, effect of wTTL was not significant. In case of section‐wise TTL supplements, TR section significantly (p < .01) improved cleavage and morula rate (58.43 ± 7.98 and 36.14 ± 6.89, respectively) followed by TA. In conclusion, present study indicates that IVM, in vitro fertilization and in vitro culture of embryo are improved in the presence of TTL, particularly its TR section. Further study is expected to reveal the principal components of TTL which may prove useful for IVM.     

Asbestos: scientific developments and implications for public policy

Asbestos is a commercial term for a group of fibrous minerals often associated with the development of pulmonary interstitial fibrosis (asbestosis), lung cancer, and malignant mesothelioma in occupationally exposed individuals. The pathogenicity of different forms of asbestos varies--long, thin amphibole fibers are most pathogenic, particularly in the induction of mesothelioma. Available data do not support the concept that low-level exposure to asbestos is a health hazard in buildings and schools. The concentration of asbestos fibers in air, type of asbestos, and size of fibers must be considered in evaluation of potential health risks.