Prevalence of subclinical ketosis in mainly pasture-grazed dairy cows in New Zealand in early lactation

Abstract

AIMS: The main aim of this study was to describe the prevalence of primary subclinical ketosis (SCK) in mainly pasture-grazed dairy cows in three dairy-farming regions of New Zealand 7–12, and 35–40 days post-calving. A second aim was to investigate herd- and cow-level factors associated with the prevalence of SCK.

METHODS: A cross-sectional longitudinal prevalence survey was undertaken in 1,620 dairy cows from 57 herds. A random sample of cows without disease in the prior 30 days were enrolled at one farm visit within 5 days of calving, and blood samples were collected 7 and 28 days later (7–12 and 35–40 days post-calving) for measurement of beta-hydroxy butyrate (BHBA) concentrations using an electronic cow-side meter. SCK was defined as blood BHBA concentration ≥1.4 mmol/L.

RESULTS: Mean cow-level prevalence of SCK varied with interval post-calving (16.8 and 3.2% at 7–12 days and 35–40 days post-calving, respectively) and age (13.0 and 13.1% of 2-year olds and ≥8-year olds, respectively, compared to 7.2% of 3–4-year-old cows). Mean herd-level prevalence of SCK was 14.3 (min 0, max 60.0)% and 2.6 (min 0, max 24.4)% at 7–12 days and 35–40 days post-calving, respectively, and was greater in Southland (13.3%) than Waikato and Canterbury herds (6.9 and 4.7%, respectively).

CONCLUSIONS: This is the first population-based report of the prevalence of SCK in New Zealand dairy herds and demonstrates that age and interval post-calving are important risk factors determining prevalence; and that there is wide variation in prevalence between herds.

CLINICAL RELEVANCE: Subclinical ketosis may be unrecognised but common in many New Zealand dairy cows in the first 2 weeks of lactation.

KEY WORDS:

• Subclinical ketosis
• beta-hydroxy butyrate
• pasture
• risk factor

Acknowledgements

The authors gratefully acknowledge the cooperation of the herd owners, and thank the technicians and veterinarians at each of the three veterinary practices involved (Anexa Animal Health, Morrinsville; Riverside Veterinary Services, Ashburton; and VetSouth, Winton) for their collection of data for this study. The authors also thank Elanco Animal Health (NZ) for funding this study.