Evaluación de estrategias de alimentación en sistemas lecheros de base pastoril de alta productividad y bajo costo operativo durante el otoño

This study was conducted between March and June 2022 at the CRS experimental station of the Faculty of Agronomy (UDELAR) in Canelones, Uruguay, where two contrasting dairy systems in terms of stocking rate and operating cost, designated “low cost” (LC) and “high productivity” (HP), were evaluated during autumn. Homogeneous groups of cows were assigned considering live weight (LW), body condition score (BCS), number of lactations, and calving date. The study was carried out on a 20.7 ha grazing platform with average stocking rates of 1.4 and 2.7 DC/ha for LC and HP, respectively, under a six-year forage rotation. The two treatments differed in the time of occupancy of grazing strips: three days in LC and one day in HP. During this period, the effect of stocking rate was analyzed on variables related to forage production and harvest, feed intake, milk yield and composition, body condition, and live weight, using a Completely Randomized Design (CRD) evaluated through Analysis of Variance (ANOVA). No significant differences were observed in daily growth rate (DGR) or forage mass between treatments, remaining within the target of 2400 kg DM/ha SEP. However, the HP system tended to achieve higher forage production per hectare (+24%), greater direct harvest efficiency (46 vs. 50%), and higher total feed intake (5464 vs. 2980 kg DM/ha). Individual reserve intake was higher in HP, whereas LC showed greater pasture intake (kg DM/cow/day), with no differences in concentrate consumption. Stocking rate influenced grazing opportunities, with LC spending more time grazing than HP (88% vs. 76%), affecting diet composition. Individual milk yield was higher in LC (+4%), while no statistically significant differences were observed in individual milk solids yield. Milk and solids production per hectare was higher in HP (+83% and +82%, respectively). No significant differences were detected in live weight or body condition. In conclusion, increasing stocking rate allowed higher efficiencies and greater production per hectare. Although intensification slightly reduced individual milk yield compared to the LC system, overall system productivity increased significantly.