Table 3. Holstein Dairy Animals Used to Study Rate of Passage for Sand Particles Weight (ke) Start End* Days of Lactation Average Milk Production (kg/day)** Average Output (kg/day) *** Feces Urine Cow No. Age (Years) 123 6 891 848 227 9.6-5.3 27.3 21.8 153 5 832 766 32 22.3-19.1 35.1 32.0 184 4 739 682 159 12.7-8.9 33.2 28.8 241 3 580 553 156 14.6~12.1 28.4 23.1 *Weight after 8 days in metabolism stalls and 9 days in outside pens. **First number listed is the average milk production before study started, and the second is for the 7 days in the metabolism stalls. **k*Averape output while confined in metabolism stalls. 154