Estrategias de alimentación en sistemas pastoriles intensivos de producción de leche contrastantes en inversión de infraestructura y simplicidad operativa

This study was conducted at the Centro Regional Sur (CRS) of the Faculty of Agronomy, located in the department of Canelones, Uruguay. The experimental period lasted four months, comprising data obtained from August to November 2021. The objective of this research was to evaluate the impact on biophysical variables of two contrasting systems in operational dedication, animal stocking rate, feeding strategy, and production cost structure during the spring season of 2021.

A system with a stocking rate of 1.82 VO/haPP, sustained mainly with forage produced within the system (within the grazing platform), using a perennial-based forage model (excluding summer forage crops), called "low cost" (BC), with an average live weight (LW) of 483 ± 20.5 kg LW and a stocking rate of 892 kg LW/ha. On the other hand, a system was implemented where productivity (l/ha) was prioritized, which implied an increase in the stocking rate (3.06 VO /haPP), with an average LW of 465 ± 27.2 kg and a stocking rate of 1416 kg/haPP. This system, called "high productivity" (AP), required the importation of corn and sorghum silage from adjacent areas.

Feeding was based on pasture consumption, adjusted to the growth rate, supplemented with additional feed if demand exceeded supply. The available pre-grazing and post-grazing kgDM was measured with the C-Dax, allowing the calculation of pasture consumption in each paddock of both systems.

The feeding structure in BC consisted of 582 kgDM/haPP/month of forage, 100 kgDM/haPP/month of reserve, and 321 kgDM/haPP/month of concentrate, while in AP it was 780 kgDM/haPP/month of forage, 385 kgDM/haPP/month of reserve, and 540 kgDM/haPP/month of concentrate.

Milk production was 1421 and 2159 kg of milk/haPP/month for the BC and AP systems respectively. To estimate solid production, the milk composition (% fat and protein) analyzed in the Colaveco Laboratory was recorded, averaging 109 kg of solids in AP and 163 kg in BC.

The forage production of both systems showed no significant differences, being 4581 kg of DM/haPP in BC and 3772 kg of DM/haPP in AP. The overall harvest was 75% and 80% in BC and AP respectively, with an instant harvest between 25-30%. Pre-grazing and post-grazing did not show statistical differences between the systems. The average forage stock was 2498 kg of DM/haSEP in AP and 2488 kg of DM/haSEP in BC.