Preference and usage of pasture versus free-stall housing by lactating dairy cattle.

The aim of the current study was to assess if cows preferred pasture or indoor housing, and how diurnal and environmental factors affected this preference. Lactating dairy cows (n = 5 groups, each containing 5 cows) were sequentially housed either in a free-stall barn on pasture, or given the choice between the 2 environments. Each group was tested 3 times under each condition, for a total of 21 d, to assess the effects of varying climatic conditions (outdoor temperature ranged from 9.9 to 28.2 degrees C and daily rainfall from 0 to 65 mm/d over the course of the experiment). When provided the choice, cows spent on average (+/- SD) 13.0 +/- 0.6 h/d on pasture, mainly at night. The time cows spent on pasture during the day decreased with the temperature-humidity index (R(2) = 0.55); time on pasture at night decreased with rainfall (R(2) = 0.12). When provided a choice, cows spent more of their lying time on pasture (69.4 +/- 0.02% of the total lying time/d) than indoors in the free-stalls. Cows also spent more time in total lying down when provided a choice than when confined to pasture [0.6 h/d more lying time; standard error of the difference (SED) = 0.21 h/d] and spent even more time lying down when confined indoors (1.1 h/d more time; SED = 0.21 h/d). Cows used the indoor housing especially for feeding; feeder use peaked when cows returned from morning and afternoon milkings. However, cows with free access to pasture spent 1.0 h/d (SED = 0.09 h/d) less time eating the TMR available indoors, resulting in a decline in intake of 2.9 kg of dry matter/d (SED = 0.36 kg of dry matter/d). How cows used the indoor housing differed when cows were provided a choice; for example, cows spent a greater percentage of their time indoors at the feed alley both during the day (47% of the total time spent indoors, versus 41% for cows confined indoors, SED = 0.02%) and at night (22 vs. 5%, SED = 0.04%). In conclusion, under the housing and environmental conditions tested, cows showed a strong preference for access to pasture at night and for access to indoor housing during the day when temperature and humidity increased.