Breed structures in Australian dairy herds.

Breed structures of Australian dairy herds over time were described for a large subset of milk-recording herds. The focus for this study was to describe the use of crossbreeding by dairy farmers, specifically proportions of herds using crossbreeding, whether they were using two-breed or three-breed crossbreeding systems, and how herd-breed structures changed over time. The most common breed structure in Australian milk-recording herds between 2000 and 2013 was two-breed crossbreeding (39% of herd-years). The next most common breed structure was purebred (35%). Over the period studied, the proportion of herds that were purebred decreased, while the proportion of herds that were crossbreeding increased (particularly three-breed crossbreeding herds). Herd-breed structures and changes over time varied with region and with the herd's calving system. There were also considerable changes in breed structure within herds, including herds changing breed structure before reverting back to their original breed structure. These results indicate that breed structures in milk-recording dairy herds in Australia are dynamic, and that farmers have commonly employed crossbreeding strategies.

Bovine digital dermatitis in Victoria, Australia.

AIMS: The objectives of this study were to estimate the prevalence of digital dermatitis (DD) in Victoria, Australia, and to investigate which organisms are consistent with typical DD lesions. The prevalence and causative pathogens of DD are not clear yet in Australia and this paper is one of the first to explore these questions in this country. METHODS: Examination and sampling of limbs was undertaken at three knackeries in Victoria, Australia. Limbs were classified as normal (N), active DD-lesion (A), dried or chronic DD-lesion (D) or suspected case of DD (S). A total of 823 cows were examined. Six skin biopsies were taken at each knackery, from which DNA was extracted for diversity profiling. Histochemical staining of samples was performed on eight of the skin biopsies. RESULTS: DD was detected in 29.8% of all cows. The prevalence of DD was significantly higher in dairy cows (32.2%) than in beef cows (10.8%). The differential abundance of Treponema-species was significantly increased in dried lesions, compared with the normal skin biopsies. Actinobacteria, Proteobacteria, Firmicutes and Tenericutes were found to be significantly different in abundance in the DD lesions compared with normal skin biopsies. Silver staining of samples showed only mild inflammation and in two samples organisms with morphology consistent with Spirochaetes were detected. CONCLUSIONS: The calculated prevalence indicates that DD is present in Victoria, Australia. The results of diversity profiling showed that the presence of Treponema-species was significantly different between the samples of DD lesions and normal skin.

Antimicrobial stewardship in the dairy industry: responding to the threat of antimicrobial resistance.

Dairy Australia is the national service body for the Australian dairy industry. Its role is to help farmers adapt to a changing operating environment and achieve a profitable, sustainable dairy industry. Although the use of antibiotics in Australian agriculture is relatively low in global terms, Dairy Australia recognises important drivers for continuous improvement in antimicrobial stewardship (AMS). Dairy Australia's first strategic priority is to support profitable farms. This priority has driven the development of a range of on-farm change management programs in the animal health and welfare fields to optimise the unit cost of production and dairy cattle welfare. Dairy Australia's third strategic priority is to further develop a 'trusted dairy industry'. Previous and current work under these two strategies position the dairy industry favourably with respect to confronting the challenge of antimicrobial resistance (AMR) and supporting sound AMS with the guiding principle of 'as little as possible, as much as necessary'. However, given an incomplete but ongoing threat of AMR, more work is needed. Supported by Dairy Australia, the dairy industry has developed an antimicrobial use strategy aligning with the Australian Animal Sector National AMR Plan 2018.

The effects on ruminal pH and serum haptoglobin after feeding a grain-based supplement to grazing dairy cows as a partial mixed ration or during milking.

Ruminal pH and serum concentrations of haptoglobin (Hp) were measured in order to assess the risk of subacute ruminal acidosis (SARA) in grazing cows offered rolled wheat grain twice daily in the dairy at milking (Control group; n= 64), or as a partial mixed ration (PMR group; n= 64) on a feedpad. Cows were allocated various levels of the supplement (8, 10, 12 or 14 kg dry matter/day). Ruminal pH was measured in 16 rumen-fistulated cows (eight PMR and eight Control group cows), using indwelling pH meters, recording every 10 min for 14 days. Serum Hp was analysed in samples collected from 125 cows. No differences in ruminal pH or serum Hp concentration were found between treatment groups, or levels of feeding. It was concluded that, using ruminal pH patterns and Hp as markers of SARA at the feeding levels used in this study, there were no differences between grazing cows fed the supplement either as grain in the dairy or as a PMR fed on a feedpad.