Lifetime survival of Jersey‐sired cows following natural challenge with facial eczema during first lactation

Abstract

During a serious natural outbreak of facial eczema (FE) in March‐May 1989 in the Northland, Auckland, and Taranaki regions of New Zealand, over 1500 Jersey‐sired 1st‐lactation heifers in 60 spring‐calving herds were blood sampled between 24 April and the end of May. The objective was to monitor their response to the FE challenge, as measured by serum activity of the enzyme gamma‐glutamyltransferase (GGT); 43 (72%) of the herds contained heifers that had been exposed. In these herds, compared with the remaining ("non‐exposed") herds, the cumulative percentages of heifers (still present for the blood sample) which were culled or had died were not significantly affected by type of herd. In the exposed herds only, the difference in log e GGT between cows culled or dead by the end of the 1 st lactation and those that survived was 0.52 ± 0.23 log e i.u. litre^–1 (P < 0.05). The survival of animals to the end of the 2nd lactation in exposed herds was 5.9% lower in heifers with serum GGT > 100 i.u. litre^–1 than in those with lower GGT levels (P = 0.05); the survival difference in heifers with serum GGT above or below a threshold of 200 i.u. litre^–1 was 9.1% (P < 0.01). From all animals blood sampled in the exposed herds (daughters from 65 sire groups), the heritabilities of survival past the end of the 1st, 2nd, 3rd, and 6th lactations following the FE field challenge were 0.01 ± 0.03, 0.02 ± 0.05, 0.02 ± 0.05, and 0.00 ± 0.05, respectively. The heritability estimate for log e GGT in the FE challenge season was 0.32 ±0.10. This study has shown significant negative associations between the GGT level after an FE challenge and cow survival.

Key words:

• facial eczema
• dairy cows
• liver enzyme
• survival
• heritability
• GGT