Efecto del método de pastoreo sobre la producción y composición de leche y desaparición de la pastura

The experiments were carried out from May 23 to June 11, from October 8 to October 25, from November 18 to December 7, 2019, at the M.A. Cassinoni, Faculty of Agronomy, Paysandú, Uruguay. The objective of this study was to compare two grazing methods (daily vs. weekly interval) and record if they influenced the performance and behavior of the dairy cow, and the rate of pasture disappearance throughout the days. To achieve this, 10 Holstein cows were used in each experiment. On the one hand, 5 cows corresponded to the weekly treatment and the remaining 5 to the daily treatment. In experiment 1, the cows accessed the pasture only in the morning shift and received supplementation. In contrast, in experiments 2 and 3, the cows were exclusively under grazing in the morning and afternoon shifts. The methods differed in the frequency of allocation of the plot, the weekly slot corresponded to 1 plot of 7 days and the daily slot 7 plots of 1 day of occupation. When the data analysis was carried out, it can be concluded that both treatments did not present differences in terms of milk production and composition. In the 3 experiments there were no significant differences (P>0.05) for height of entry and exit of the plot when comparing daily treatment with weekly. In experiment 1, the average inlet height was 16.3 ±1.04 cm and 10.6 ±0.23 cm for outlet. For experiment 2 it was 17.6 ±0.95 cm at the entrance and 11.9 ±0.83 cm at the exit. For experiment 3 it was 28.1 ± 0.89 cm and 16.3 ± 1.37 cm for outlet. When analyzed to compare the milk production of both grazing methods, no significant differences were found (P>0.05) for milk production (L/day). In experiment 1, productions of 27.0 ±2.38 L/day were obtained. In the second experiment it was 20.8 ± 0.69 L/day. Finally, in experiment 3 the values were 14.7 ±0.66 L/day. The time dedicated to grazing was 196, 535 and 592 min/cow/day for experiment 1, 2 and 3, respectively. Therefore, there were no significant differences (P>0.05). Regarding the number of grazing sessions performed by the cows, they performed 3 sessions in experiment 1 where they only grazed one shift a day, and 7-8 sessions in experiments 2 and 3 where they grazed double shift. As we have been able to verify, the daily treatment and the weekly treatment do not present significant differences in terms of production and composition of daily milk per cow. In addition, it was not possible to record differences in the behavior of the animals and in the disappearance of the pasture throughout the days in each experiment.