A retrospective study on the effects of dry period length on milk yield and postpartum health in Holstein dairy cows.

Abstract

We retrospectively analyzed the effects of dry period length (DPL) on milk yield and postpartum health using 152 commercial dairy farm data, including 46,228 dairy cows in Hokkaido, Japan, and examined the optimal DPL. The DPL was divided into eight categories: ≤25, 26-35, 36-45, 46-55, 56-65 (reference), 66-75, 76-85, and ≥86 d. The total milk yields (the sum of milk yield during the 55 d before and the 305 d milk yield after calving) of cows with DPL of ≤55 d did not differ from the reference group. Cows with DPL of ≤55 d had lower odds ratios (OR) of a displaced abomasum (DA), ketosis, milk fever (MF), and abnormal milk fat-to-protein ratio but had higher puerperal fever (PF) and stillbirth ORs than the reference group. Cows with a DPL of 46-55 d had the lowest PF and stillbirth ORs among the short DPL categories. The extremely short (≤25 d) and long (≥86 d) DPL increased the ORs of mastitis and abnormal liner score of somatic cell counts (SCCs) compared with the reference group. We conclude that shortening DPL can reduce postpartum health problems without reducing milk yield and that the optimal DPL is 46-55 d.