Livestock disease threats associated with intensification of pastoral dairy farming.

This paper provides an overview of the changes in the pasture-based dairy systems of New Zealand and Australia that may influence the health of cattle. There are relatively few available data that can be used to quantify the effects of increased intensification of milk production on the health of cattle. There is evidence that increased production increases the risk of mastitis and culling for udder health. Increased risks of mastitis with treatment with somatotropin support these findings; however, the risk of mastitis may decrease with increased milking frequency. Larger herds with greater stocking density should increase the risk for infectious disease, but evidence to support this contention is sparse. Very intensive grazing patterns associated with higher grass yields achieved using better cultivars and greater use of fertilisers favour nematode parasites. There is some evidence of anthelmintic resistance in both nematodes and liver fluke. Veterinarians will need to be aware of the potential for these to reduce the productivity of cattle. There have been benefits of improved nutrition on the efficiency of energy use for dairy production. Diseases such as bloat and ketosis appear to be of lower prevalence. It also appears that mineral nutrition of pasture-fed cattle is being better addressed, with gains in the control of milk fever, hypomagnesaemia and trace-element deficiencies. However, acidosis is a condition with a high point prevalence in pasture-based dairy systems where cows are fed supplements; one study in Australia found a point prevalence of approximately 11% of cows with acidosis. There is evidence from this study that the neutral detergent fibre (NDF) in pasture-based diets may need to be higher than 30% of the diet to maintain rumen stability. Laminitis and acidosis are different conditions with a similar pathogenesis, specifically highly fermentable diets. The prevalence of lameness was 28% in herds in Australia, suggesting that this condition must be a focus for preventive medical approaches, including the design of laneways, feed pads and dairies.

Locomotive disorders associated with sow mortality in Danish pig herds.

Given the increase in sow mortality in Danish pig herds over the last 10 years, we have investigated the causes of spontaneous death and killing of sows, especially those due to locomotive disorders. A total of 265 culled sows (93 spontaneously dead sows and 172 killed sows) from 10 different herds were sent for complete necropsy, and grouped according to primary diagnoses. From 35 of these sows, tissue for histological evaluation and samples for bacteriological cultivation were also collected, and secondary diagnoses and body condition were recorded. The main causes for killing were related to the locomotive system (72%), arthritis (24%) and fractures (16%) being the most frequent lesions. The main causes of spontaneous death were related to the gastrointestinal system and spleen (45%) and the reproductive system (24%). Arthrosis was a secondary diagnosis in 88% of the killed sows and in 92.5% of the spontaneously dead sows. Arcanobacterium pyogenes was the main cause of arthritis. The killed sows had significantly lower body condition compared with spontaneously dead sows. The first two parities and the time around farrowing were associated with the highest mortality in both groups. Hopefully, these observations can guide breeding units attempting to monitor, control and reduce sow mortality.