Environmental mastitis in intensive high‐producing dairy herds in New South Wales

Objective To determine the prevalence of mastitis pathogens in high‐producing intensive dairy herds in New South Wales. Design Field survey. Procedure Milk samples from the mastitis‐affected quarter were collected from cows on five high‐producing dairy farms in NSW. The 820 samples were cultured using standard microbiological culture techniques. Results Bacteria or fungi were isolated from 83.3% of samples (683/820). More than two colony types were isolated from 16.7% of samples (137/820), two types from 6.6% (54/820), and one type from 52.3% (429/820). No bacteria were isolated from 24.4% (200/820) of the primary cultures, but enrichment cultures of these samples yielded single colony type bacterial isolates from 36.5% (73/200) of samples. Environmental pathogens, including coliforms, environmental Streptococcus and Staphylococcus spp., made up 91% (555/610) of isolates and accounted for 33.6% (205/610), 41.6% (254/610) and 15.7% (96/610), respectively, of isolates. Escherichia coli accounted for 76.1% (156/205) of the coliform isolates, Streptococcus uberis and Streptococcus dysgalactiae accounted for 32.3% (82/254) and 28.0% (71/254), respectively, of the environmental streptococcal isolates. Contagious pathogens were uncommon, comprising only 2.5% (15/610) of the total isolates. Conclusion The incidence and causes of mastitis are largely influenced by farm management. The relatively high prevalence of coliform mastitis in the intensive high‐producing herds in this survey contrasts with the low incidence reported in surveys of pasture‐based herds in Victoria. If the Australian dairy industry continues its current trend of intensification, coliform intra‐mammary infections may emerge as an increasingly important cause of mastitis.     

Prevalence, spread and control of caprine arthritis-encephalitis virus in dairy goat herds in New South Wales

SUMMARY A study of the prevalence, spread and control of caprine arthritis-encephalitis virus (CAEV) in dairy goat herds in New South Wales (NSW) during 1986–1988 found that 56.8% of 1484 goats in 14 dairy herds were infected with CAEV. The prevalence of CAEV infection within most herds not implementing control measures increased during the study. At the end of the study, 59.7% of 1322 goats were infected. The prevalence of CAEV increased with age. Differences between breeds were less apparent. Within seven herds with a high standard of identification of goats, 149 of 812 goats seroconverted in an ELISA. Of these newly infected goats, 142 (95.3%) were > 1 yr of age and 96 (64.4%) were > 2 yr suggesting lateral spread of the virus. Most of the goats > 2 yr of age had been in the milking herd for a minimum of 3 to 6 months. The high seroconversion rate within the milking herd suggested that factors other than the ingestion of infected colostrum and milk before weaning were important for the spread of CAEV. Observations indicated that behaviour of goats, particularly reproductive behaviour among lactating does, and milking herd management practices are important in the spread of CAEV. A high density of livestock, poor livestock control and contamination of feed, water, equipment and personnel were implicated in transmission. Poorly functioning milking machines may also be involved. CAEV was eradicated from 3 herds by the implementation of strict control measures.     

Reproductive performance in South Australian dairy herds

SUMMARY Herd breeding records (161) were examined from a random 10% sample of dairy farms (96) in South Australia with more than 40 cows and suitable breeding records for 1988 and/or 1989. Of these farms, 53 (55.2%) had a year-round calving pattern, 42 (43.8%) claimed to be seasonal and one was changing from a year-round to a seasonal pattern. Only 14.6% of farmers observed oestrous behaviour outside milking times and 18.8% used tailpaint. Overall, the average proportion of unobserved heats was estimated to be 32%. Artificial insemination (AI) was carried out on 85.4% of farms (16.7% used AI alone and 68.7% also used bulls) of which 32.9% used commercial technicians and 67.1% were do-it-yourself operators. Overall, the average 30-day submission rate was 59.9% and the average 49-day non-return to service rate was 58.9%. Investigation into the probable causes of suboptimal reproductive performance gave a tentative diagnosis of inefficient oestrous detection, deferral of service, inadequate nutrition, poor AI technique, insufficient bulls, and venereal/other diseases in 69.1, 32.1, 27.2, 28.4, 13.6 and 7.4% of records, respectively.     

The epidemiology of subfertility in non-seasonal calving dairy herds in the Camden region of New South Wales: preliminary investigation of risk factors

OBJECTIVE: To investigate relationships between biographic, reproductive, production and disease traits and subfertility among 965 Holstein cows from 10 non-seasonal calving dairy herds in the Camden region of New South Wales. DESIGN: A retrospective case-control study METHODS: Biographical, disease and reproductive data were collated from computerised records for cows with lactations that commenced between 1 July 1995 and 30 June 1996 and univariable and bivariable associations with subfertility were determined. RESULTS: Records from 965 cows that conceived were considered for risk factor analyses. Associations between subfertility and a number of risk factors (P < 0.3) were detected. Significant (P < 0.05) risk factors for subfertility in multiparous cows included herd of origin and, after controlling for the effect of herd, subfertility in the previous lactation, greater than 62 days dry, parity greater than five, interval between calving and first recorded heat, metritis and cystic ovarian disease. Herd of origin and, after controlling for herd effects, dystocia, metritis and percentage of milk fat plus protein at the time of first service were significant (P < 0.05) risk factors for subfertility in primiparous cows. The direction and magnitude of these associations are presented. CONCLUSION: Subfertility has a similar rate of occurrence in the herds examined to that reported overseas. Although herd of origin has a substantial effect on individual risk of subfertility, cow-level risk factors for subfertility are likely to exist. Exposures differ between primiparous and multiparous cows.     

Kunjin flaviviral encephalomyelitis in an Arabian gelding in New South Wales, Australia

Flaviviruses, including Kunjin virus, are arboviruses that cause encephalomyelitis in humans and horses. This case report describes an Arabian gelding exhibiting neurological signs of flavivirus encephalomyelitis, the diagnostic investigation and confirmation of an unreported case of Kunjin virus equine encephalomyelitis in Australia.     

A report on surveys of the incidence of mastitis infection in New Zealand dairy herds

Extract

New zealand holds a leading position among the world's exporters of dairy produce. In most dairying countries, mastitis is considered a major disease problem and certainly this is true in New Zealand, but until now there has been very little published evidence on the incidence of the disease in this country.     

Significant features of the epidemiology of equine influenza in New South Wales, Australia, 2007

Equine influenza (EI) was first diagnosed in the Australian horse population on 24 August 2007 at Centennial Park Equestrian Centre (CPEC) in Sydney, New South Wales (NSW), Australia. By then, the virus had already spread to many properties in NSW and southern Queensland. The outbreak in NSW affected approximately 6000 premises populated by approximately 47,000 horses. Analyses undertaken by the epidemiology section, a distinct unit within the planning section of the State Disease Control Headquarters, included the attack risk on affected properties, the level of under-reporting of affected properties and a risk assessment of the movement of horses out of the Special Restricted Area. We describe the epidemiological features and the lessons learned from the outbreak in NSW.     

Risk factors for repeat-breeder syndrome in New South Wales dairy cows

A retrospective case-control study involving 1041 cow lactations from 10 commercial dairy herds in Australia determined relationships between biographic, production, reproductive and disease factors and repeat-breeder syndrome (RBS) (conception to greater than two inseminations). The study population was stratified into primiparous- and multiparous-cow sub-groups and logistic regression was used. Effects of herd were examined by including this variable alternatively as a fixed and a random effect. In the primiparous-cow fixed-effect model, the risk of RBS was increased with post-calving metritis, stillbirth, and with increasing days taken to reach peak milk yield, and reduced following dystocia. An inverted U-shaped relationship with total milk-solids percentage at the time of first service was detected. In the multiparous-cow fixed-effect model, the risk of RBS was increased in cows with chronic metritis, cystic ovarian disease (COD), in cows of parity >5 and in cows that were sub-fertile in the previous lactation. Increasing days to first recorded heat (DFH) reduced risk of RBS and a non-linear relationship with average 120-day milk-protein percentage was found. When herd was fitted as a random effect, stillbirth and 120-day average milk-protein percentage were no longer significant in the primiparous and multiparous models, respectively. The study emphasises the need to control appropriately for the clustering effect of herd and supports the need to minimise periparturient disease and improve nutrient balance to achieve optimal fertility in dairy herds.