Calving interval and timing of first artificial insemination with higher milk yield in 1000 days from first calving in Holstein cows

Abstract

We investigated calving interval （CI） and timing of first artificial insemination （AI） with higher milk yield （MY） in 1000 d from first calving （1000dMY）. Data were test-day record of 24,476 Holstein cows from first to third lactation collected in Hokkaido, Japan. The lactation curves were adapted to test-day records to estimate 1000dMY. Data contained only cows with first to third calving. Median of CI were 385 d between first and second calving and 396 d between second and third calving. Higher 1000dMY were obtained when both CIs were ranging from 357 d to 440 d. When CI were longer than 440 d, 1000dMY were gradually decreased. Because of gestation period were about 280 d, higher 1000dMY would be produced when first AI were started after 80 d from calving.