Abstract :
[en] The Ecuadorian inter-Andean valley maintains large agricultural areas called haciendas whose main activity is milk production, surrounding these, we find small and medium producers also considered ranchers. Although both are oriented towards the same markets and implement a clear trend towards intensive production systems, they show a marked difference in the dynamics of productive activity despite sharing similar constraints in term namely of altitude and marked slopes for their pastures. To enhance productive yields, the most extensive and effective application of improved management is sought for by farmers. Options to reach this objective include the composition of herds, the size of the paddocks, the stocking rate and resting times of the meadows, the use of fertilizers, an efficient combination between agricultural crops and pasture renewal and stoking management methods, the latter being possibly one low cost short-term action lever to act upon in order to potentiate dairy farming productivity. However, it is difficult to predict the efficiency and profitability of such efforts, particularly when there is such a distant economic and cultural gap between ranchers in the same country. To the best of our knowledge, the link between grazing management and milk productivity has not been documented in high-relief situations. Our thesis aims to analyze the impact of stocking management methods on the productive performance of grazing cows, in intensive milk production in the Ecuadorian highlands. In addition to analyzing the influence of the relief in the decision making for the conformation of paddocks, in the context of different degrees of slope on the properties. We hypothesized that a grazing management system can be found that is better adapted to the organizational practices of dairy systems in the Ecuadorian tropical highlands, as well as identify some practices that better compensate for the detrimental effects of slopes on animal productivity. To do this, first, 42 milk-producing farms were characterized in different cantons of the rural area of the province of Pichincha (Quito, Mejía, Rumiñahui and Cayambe) of Ecuador. Through a questionnaire to identify the productive and management activities in the herds and evaluate the average slope of the pastures of the farms based on GIS data. The results showed that the farms had an average area of 40 ha, the herds were composed of 60 ± 63 milking cows, predominantly of the Holstein Friesian breed (65 %), and the daily production of cows in milk reached 15.1 ± 3.4 kg. The highest productivity was found in the farms using rotational stocking with high intensity of instantaneous grazing with very short occupation times (< 12 h), cultural tasks in the meadows (reseeding, resting time, equalization cuts, soil aeration, fertilization, manure dispersion) and a flat topography of the pastures (p < 0.05). The steepness of the slopes was not a limitation to establish pastures for grazing animals since pastures were observed in the entire range of slopes, including very steep ones (up to 55 %). The daily production of individual cows was negatively correlated (r = - 0.323, p = 0.037) with the average slope of the surveyed farms. Subsequently, we conducted two grazing experiments to determine the ingestive behavior of dairy cows, under the types of pasture rotation mostly used by farmers in the survey (from rotational stocking with long occupation time to grazing with very short occupation times of 3 hours), to test the relevance of rotations with shorter occupation times on the performance of the system. A first experiment was done on flat paddocks applying three rotational stocking contrasting treatments ranging from very short to long occupation times: three hours, 24 hours and seven days respectively of 7 days. Cows in the long occupancy time treatment spent more time eating, tended to have a higher average speed during forage intake, attributed to a greater displacement per exploration of the entire area assigned for the experimentation time. In the 3-h treatment, greater inactivity was perceived in anticipation of the opening of new areas for grazing during the day. Despite these differences in activity, milk production did not differ in quantity or quality (ie, fat, protein, non-fat solids, total solids). Showing that under grazing conditions with an intermediate forage allocation on flat paddocks and with low producing cows, the application of a labor-intensive stocking method that requires opening new areas every 3 hours does not lead to a significant increase in the production. Next, we carried out a second grazing experiment in which two stocking methods (long occupancy and very short occupation) on a terrain with moderate relief and with up and downhill displacement of cows on the pastures to harvest the forage. Results showed that cows that grazed the very short time treatment moved more during meals than those placed in the long occupation time treatment. This is explained by the fact that the sub-paddocks 3 hours were designed horizontally to favor lateral walking and avoid the effect of the slope on displacement. While the herd that had freedom of movement throughout the paddock (long occupation time), traveled less (-27 %), leaving higher stubble height in postgrazing (7 cm). Higher volumes and concentration in solids were found in milk for the herd that grazed in the treatment with assignment of new subpaddocks every three hours.
In conclusion, the combination of grazing management systems with operations that better compensate for the detrimental effects of slopes promote productive yields in dairy farms in the Ecuadorian highlands. The allocation of forage material must be based on a rotation with occupation times that adjust to the slope of the paddocks. Avoiding the unnecessary use of human and economic capital where it does not justify the implementation of shorter rotation times (flat paddocks), guaranteeing the optimization of resources, higher volumes and better quality of the milk produced. Finally, farmers can manage their agricultural processes using the proposals developed in this research according to the resources available in their environment.
