Effect of a 2-h daily exit on milk quality, activities and outside behavior of lactating cows

This study investigated the effect of a 2-h daily exit on milk traits and behavior of dairy cows. A 4-week trial was conducted using 10 lactating cows divided into two homogeneous groups for DIM (129.2 ± 18.8), parity (3.0 ± 1.4) and absence of mastitis and lameness. The experimental design was a crossover (2 groups × 2 periods), so each group was alternatively under treatment IN or OUT in each period. The IN group remained inside a free-stall, while the OUT group had a 2-h daily exit (15:00-17:00) to a short-mowed grass paddock. Milk yield, milk quality, and activities were monitored via individual collars linked to the automatic milking machine. Activities included the number of milkings, feeding (min/d), compound feed intake (kg/d), and rumination (min/d, min/h). Outdoor behaviors were monitored using six digital video cameras covering the paddock area (1,500 m²) and connected to a video recorder. Recordings were analyzed by a trained observer. Climate data (relative humidity, temperature, wind speed, solar radiation, rainfall) and the adjusted Temperature-Humidity Index were used to better understand outside behaviors. Statistical analysis followed a mixed model. Results showed a higher daily number of milkings for the IN group (3.02 vs. 2.88; p < 0.05), but no differences in milk production (on average 32.6 kg/d) or milk quality traits such as: fat, lactose, and SCS. Milk protein was higher for the IN group (4.81 vs. 4.80%). Eating behaviors were not affected by the treatment with a daily average of 236 min of feeding and 4.53 kg of compound feed intake. Daily rumination was higher for the IN group (485 vs. 472 min), due to the lower rumination of the OUT group during the exit (at 16:00) (19 vs. 7 min) that may have been affected by the grass in the paddock. The main outdoor behaviors were standing (60.45%), grazing (38.10%) and ruminating (11.81%). Rainfall affected (p < 0.05) walking, standing, positive interaction, playing and sexual behavior. In conclusion, offering lactating dairy cows a 2-h daily exit in the afternoon is an effective management system, allowing cows to exhibit natural behavior while maintaining milk production and composition comparable to a full indoor system.