Association between ketosis dynamics and fertility in dairy cattle from time-series measurements

Abstract

Due to the innovation of farming technology, biomarkers in milk can be measured frequently while milking and instant conditions of cows are available to farmers. The objective of this retrospective observational cohort study was to evaluate the association between ketosis dynamics and fertility in dairy cattle. Two-year time-series data from 4,041 dairy cows in 38 Dutch dairy farms were provided by DeLaval Herd Navigator (HN). Milk β-hydroxybutyrate (BHB) and progesterone (P4) are indicators of ketosis and fertility, respectively. Three Cox proportional hazard regressions were used to analyze days from calving to resumption of cyclicity, first heat, and first artificial insemination (AI), respectively. Poisson regression was used to analyze total number of inseminations. As a result, cows with higher average milk BHB in the first 20 days in milk (DIM) were found to have longer time intervals to resumption of cyclicity, first heat, and first insemination. Within the first 2 months after calving, cows reached maximum BHB later, the cows would have earlier first heat and fewer number of inseminations. Average milk yield in the first 60 DIM was found significantly to have effects on first insemination and number of inseminations. Days from calving to resumption of cyclicity, first heat, and first insemination are good fertility indicators for early lactation period, while number of inseminations is highly associated with milk production. Milk yield might be a crucial consideration for inseminations.