Exploring intensification strategies of pasture-based dairy systems in Uruguay: high-productivity and inputs vs. medium-productivity and simpler systems

Lucía Gil-Zibil^*Gastón OrtegaDiego CustodioMaría Pía BriñónPablo Chilibroste^*

• Universidad de la Republica Facultad de Agronomia, Montevideo, Uruguay

Intensification in pasture-based dairy systems has led to greater external inputs, increasing the risk of nutrients losses to the environment. There is limited information in Uruguay on how intensification strategies affect productivity and nutrient balances at the farm scale. This study compared productive variables and farm-gate nutrient balances of nitrogen (N), phosphorus (P) and potassium (K) under two pasture-based dairy intensification strategies over three fiscal years (July 2021-June 2024). Two intensification strategies were evaluated in a three-year completely randomised block design: 1) High Productivity (HP), with 2.8 cows ha-1, used bought-in conserved forage and concentrates; and 2) Medium Productivity (MP), with 1.7 cows ha-1, self-sufficient in conserved forage, bought-in concentrate and simplified management. Cows were paired by calving date, body condition score, body weight and previous milk yield, then randomly assigned to each system. Farm-gate nutrient balances accounted for inputs from feeds, fertilisers, biological N fixation and atmospheric deposition, and outputs from milk, live weight changes and bedding materials. Data were analysed using linear mixed models, with treatment and year as fixed effects and blocks as random effect. No significant differences were observed in forage production between both systems; however, HP relied more on harvesting by grazing (7,073 vs. 4,782 kg DM ha-1, HP and MP respectively; p<0.05), whereas MP had higher mechanical harvest (473 vs. 1,862 kg DM ha-1, HP and MP respectively; p<0.05). Milk (22,178 vs. 13,606 kg milk ha-1), and solids (1,907 vs. 1,184 kg solids ha-1) productivity were significantly higher for HP than MP. Regarding nutrient inputs, feed was the main source of N for HP, whereas fertiliser for MP. For nutrients P and K, feed was the greatest input in both systems. Nutrient surpluses for N, P and K were 312 vs. 205, 82 vs. 50, and 128 vs. 44 kg ha⁻¹, for HP and MP, respectively. Nutrient use efficiency was not significantly different between treatments. Time in confinement was higher for HP (55% vs. 37%), highlighting the importance of infrastructure and effluent management under higher intensification strategies. Moreover, effluent re-utilization emerged as an opportunity to improve nutrients use efficiency in intensified systems.