ATLANTO-AXIAL MALARTICULATION IN ANGORA GOATS

SUMMARY Two male Angora goats presented with ataxia and weakness of the hind limbs. Both tired easily when exercised and often stumbled and fell. In both cases, post-mortem examination revealed focal areas of gliosis and diffuse Wallerian degeneration in the spinal cord at the level of the atlanto-axial joint. There were also two areas of myelomalacia in one of the goats. In the other, the caudal articular surfaces of the atlas were unusually convex and the odontoid process of the axis was laterally compressed. It is suggested that these vertebral anomalies resulted in excessive mobility of the joint leading to the development of a compressive myelopathy.     

Identification of envelope and nucleocapsid proteins of infectious bovine rhinotracheitis virus by SDS-polyacrylamide gel electrophoresis

Infectious bovine rhinotracheitis (IBR) virus was purified by rate zonal and isopycnic centrifugation in potassium tartrate gradients. Viral nucleocapsids were isolated from purified virions by treatment with the nonionic detergent Triton X-100 followed by high speed centrifugation. This treatment was shown to produce a suspension of 74% completely de-enveloped nucleocapsids, 24% incompletely de-enveloped nucleocapsids, and 2% whole virions. The viral nucleocapsids contained DNA and banded at a density of 1.25 g/cm3. Analysis of the viral polypeptides by gradient SDS-polyacrylamide gel electrophoresis revealed that 33 virion proteins, ranging in molecular weight from 13,000 to 275,000 dalton, were present in the complete virus particle. Detergent treatment of the virus quantitatively removed two of the major proteins (vp8, 90,000 dalton, and vp13, 73,000 dalton) and partially removed eleven other proteins. Fifteen viral polypeptides appeared to remain firmly associated with the viral nucleocapsids.     

Monitoring and surveillance in abattoirs of residues of antibacterial substances – a description of programs in Australia and the USA

SUMMARY Australia and the USA are major international meat exporting countries. Both countries conduct programs to monitor and survey for antibacterial residues. Australian programs use a urine screening test, whereas the US programs use tissue fluids as the test medium. The development of surveillance programs to provide rapid feedback to producers is a feature of the Australian programs. The programs in each country compare favourably with regard to numbers of animals tested, results and action taken to prevent residues. The results of the Australian programs justify the promotion of a ‘clean food’ image for Australian meat products with respect to antibacterial drugs.     

Recent Developments in Oestrous Synchronization of Postpartum Dairy Cows with and without Ovarian Disorders

This report reviews the most recent developments in prostaglandin‐based oestrous synchronization programmes for postpartum dairy cows and addresses the efficiency of controlled breeding protocols based on such developments for cows with abnormal ovarian conditions. A double prostaglandin protocol applied 11–14 days apart seems to be capable of bringing most cows to oestrus. Because of varying oestrus onset times, improved conception rates are obtained following artificial insemination (AI) at detected oestrus rather than fixed‐time AI in prostaglandin‐treated cows. The administration of oestradiol or human chorionic gonadotrophin, or both these hormones, after prostaglandin treatment, improves the synchrony of oestrus yet does not enhance the conception rate. Progesterone‐based treatments for oestrous synchronization are considered the most appropriate for non‐cyclic or anoestrous postpartum dairy cows; prostaglandin alone being ineffective because of the absence of a mature corpus luteum in these cows. Improved oestrus synchrony and fertility rate have been reported using short‐term progesterone treatment regimes (7–9 days) with or without oestradiol benzoate combined with the use of a luteolytic agent given 1 day before, or at the time of, progesterone withdrawal. The ovulation synchronization (Ovsynch) protocol, based on the use of gonadotrophin releasing hormone and prostaglandin, was developed to coordinate follicular recruitment, CL regression and the time of ovulation. This protocol allows fixed time insemination and has proved effective in improving reproductive management in postpartum dairy cows. However, timed AI following Ovsynch seems to have no beneficial effects in heifers, because of an inconsistent follicle wave pattern, and in anoestrous cows, given their lack of prostaglandin responsive CL. To date, there are several prostaglandin based, fixed‐time insemination oestrous synchronization protocols for use in early postpartum dairy cows with ovarian disorders such as ovarian cysts and acyclicity.     

Effect of age of the laying hen on the composition of the egg

1. All eggs laid by a group of 16 light‐body‐weight hens during the laying year were weighed and divided into yolk, albumen and shell and the wet and dry weights of the components determined.

2. After an initial period of about 2 months, the weights of egg, water, wet albumen, wet and dry yolk increased with age, whereas those of dry albumen and wet and dry shell remained constant. Dry shell per square centimetre surface area decreased with age but water per square centimetre surface area remained constant.     

The development of a formulated feed containing Ulva (Chlorophyta) to promote rapid growth and enhanced production of high quality roe in the sea urchin Tripneustes gratilla (Linnaeus)

This study investigated growth and gonad production of Tripneustes gratilla fed four protein‐rich artificial diets supplemented with varying amounts (0%, 5%, 15% and 20% weight/weight (w/w); designated 0, 5, 15 and 20U, respectively) of the macroalga Ulva over a 12‐week period. Gonad size, texture, colour and a number of production performance parameters were quantified and compared with urchins fed fresh Ulva (FU) and a combination of FU and artificial feed (FB). All artificial diets significantly (P ≤ 0.05) increased gonad somatic indices (GSI) compared with the FU treatment. The 20U treatment increased GSI by 205% by week 9, compared with a 57% increase in the GSI of urchins fed FU. Gonad colour was calculated using three colour parameters, namely L* (lightness), a* (redness) and b* (yellowness). Whereas L* and a* values did not differ significantly between treatments, b* values for all treatments, with the exception of the 20U and FB treatments, were significantly (P ≤ 0.05) lower or less yellow than the FU treatment by week 12. These results show that we have successfully formulated a feed (20U) which can produce commercially acceptable gonads in terms of both size and colour, indicating the potential for this artificial feed to support commercial echinoculture.     

Some Factors Affecting the Abortion Rate in Dairy Herds with High Incidence of Neospora‐Associated Abortions are Different in Cows and Heifers

The aim of this study was to determine if the factors affecting the abortion rate in dairy herds with high incidence of Neospora‐associated abortions are different in pregnancies of cows and heifers chronically infected with Neospora caninum. In heifers (n = 229), an increase in the cumulative number of days with a mean relative humidity (RH) lower than 60% during the second trimester of gestation increases the risk of abortion. Yet, the likelihood of abortion was 7.6 times lower for pregnant heifers inseminated with Limousin bull semen, compared with those inseminated with Holstein‐Friesian bull semen. In pregnancies of parous cows (n = 521), an increase in rainfall and in the cumulative number of days with a mean RH lower than 60% during the second trimester of gestation increased the abortion rate. However, in contrast, an increase in the lactation number produced a decrease in the abortion rate, with a likelihood of abortion 4.8 times lower for pregnant cows inseminated with Limousin bull semen, and three times lower for those inseminated with Belgian Blue bull semen, compared with dairy cows inseminated with Holstein‐Friesian bull semen. Finally, the likelihood of abortion was 3.2 times lower for pregnancies of parous cows with low antibody titres against N. caninum (6–30 units) as compared to those with high antibody titres (≥30 units), whereas in heifers this variable had no effect. The practical recommendations of the present study include the control of the cow environment during the second trimester of gestation, the priority of culling for parous cows with higher antibody titres against N. caninum and the insemination of Neospora‐seropositive cows with semen from the Limousin breed.