Why Reevaluate Dry Period Length?

Abstract

Possible advantages of reducing length of dry period include increased income from milk production, simplified dry cow management, decreased metabolic disorders, and alleviation of overcrowded dry cow facilities. There is abundant data to support a 60-d dry period to maximize milk yield the next lactation. The great majority of data is from studies using farm records (e.g., DHI data). In these data sets, cows with less than 6-to 8-wk dry periods probably were not intended to have short dry periods and consequently were not managed for short dry periods. Additionally, recommendations from observational data may be biased due to interactions, e.g., between milk yield and length of dry period. Some experiments specifically designed to compare 30and 60-d dry periods indicate that shorter dry periods are possible without sacrificing milk production the next lactation. There is a paucity of data to determine the effects of shortening the dry period on milk composition, metabolic disorders, and reproductive performance. The limited amount of information that is available indicates that shortening the dry period will probably not have negative effects on these parameters and may have slight beneficial effects. In some cases, the beneficial effects may have resulted, in part, due to negative effects on milk production. Cows with longer calving intervals and older cows may be more likely to avoid negative effects of shortening dry periods on subsequent milk yield. Shortening the dry period by initiating milking after a dry period but prior to parturition does not increase milk yield or improve animal health sufficiently to warrant consideration. Several studies indicated complete elimination of the dry period results in a 20 to 25% decrease in milk yield the following lactation. However, these studies have utilized low cow numbers and cows with extremely low milk production. As milk yield and persistency of lactation increases, either through genetic