Effect of a daily outdoor access on the urination and defecation behaviors and nitrogen excretion by lactating cows

This study aimed to assess the urination and defecation frequency along with the nitrogen excretion produced by lactating cows spending either 2 or 4 h a day in an outdoor exercise area, to then estimate the load of cows allowed considering the nitrogen limitation in manure established by the EU directive. Six Italian Simmental lactating cows housed in a free-stall were paired and alternatively subjected to the following exit managements: no daily outdoor access, a 2-h daily outdoor access (U2; from 11:30 a.m. to 1:30 p.m.), and a 4-h daily outdoor access (U4) divided into a morning (U4a; 9:00 to 11:00 a.m.) and an afternoon (U4b; 2:00 to 4:00 p.m.) exit. Using a crossover design, each pair of cows was subjected to each exit management for a period of 2 weeks, then switched twice, until the completion of 6 weeks of evaluation in order to ensure all the three different group combinations. The study considered as treatments the two exit managements: U2 and U4. Cows in the paddock urinate...