Livestock disease threats associated with intensification of pastoral dairy farming

Abstract

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.

Invited review: Use of meta-analysis in animal health and reproduction: Methods and applications

“…For example, milk fever, dystocia and abomasal disorders (white bar), ketosis, retained placenta (gray bar), and metritis, mastitis and lameness (black bar). From Lean et al (2008). definition in studies can lead to problems of interpretation in meta-analysis.…”

Scientific Opinion on the assessment of dairy cow welfare in small‐scale farming systems

“…There is low prevalence of bloat and ketosis in intensive pasture-based systems, while acidosis has a high point prevalence (Lean et al, 2008). Mean herd-level prevalence of subclinical ketosis in New Zealand was 14.3 and 2.6 % at 7-12 and 35-40 days post calving, respectively (Compton et al, 2014), and in a grazing production system was 10.3 % between 4 and 19 days in milk (Garro et al, 2014).…”

Using a One Health approach to assess the impact of parasitic disease in livestock: how does it add value?

“…This intensification, together with changing management practices, alters the distribution and intensity of parasite infections. For example, increased stocking rates and more productive pastures increases faecal matter in the pasture whilst decreasing grazing intervals, with the combined effect of increasing the concentration of parasitic larvae that livestock are exposed to (Lean et al, 2008). The major impact of parasitic disease in livestock is now due to sub--clinical infections causing production losses, which are increasingly important because of low profit margins in the livestock sector.…”