Efecto del manejo del pastoreo en la recría de borregas en campo natural

This study was conducted at the Palo a Pique Experimental Unit of INIA Treinta y Tres, Uruguay (33°15'10''S, 54°30'15''W, at 45 m above sea level), located in the Sierras and Lomadas del Este region, within a 30-year long-term experiment (LTE). This Final Degree Project was developed using data from the first three years of the experiment (2021–2022, 2022–2023, and 2023–2024). The central issue addressed is how grazing management, through different grazing intensities based on sward height, affects forage structure and animal production. In this context, the objective is to identify the optimal sward structure(s) for proper management, aiming to achieve higher animal productivity. This would allow for increased production and reduced risk under adverse conditions (e.g., drought).The experimental design was a randomized complete block design with four different forage structures based on pasture height (T4 = 4 cm, T8 = 8 cm, T12 = 12 cm, and T16 = 16 cm). Key variables such as sward height, forage mass, stocking rate, individual live weight gain, and productivity per unit area were estimated. Climatic monitoring was carried out using records from the on-site weather station. For data analysis, mixed linear models were applied using R software. For forage-related variables (height and biomass), treatment was considered a fixed effect, while block, measurement, and year were treated as random effects. For animal production variables (individual and per-hectare gains), treatment was also considered a fixed effect, and block and year as random effects. Pairwise comparisons between treatments were performed using Tukey’s test, with a significance level of 5%. The average pasture heights for each treatment were 3.8 cm for T4, 7.9 cm for T8, 10.1 cm for T12, and 12.3 cm for T16, with the latter two not reaching the target heights. Regarding forage mass, significant differences were observed among treatments (T4 = 508 kg DM/ha; T8 = 1,731 kg DM/ha; T12 = 2,313 kg DM/ha; T16 = 2,682 kg DM/ha). Results indicated that the higher height treatments (T12 and T16) promoted greater individual weight gain (0.048 and 0.051 kg/animal/day, respectively), while the lower height treatments (T4 and T8) optimized productivity per hectare, albeit with lower individual performance (0.035 and 0.041 kg/animal/day, respectively). In conclusion, treatments T8 and T12 promoted the best functional balance between pasture structure, individual gain, and productivity per hectare of the ewe lambs. This intermediate height range (8–12 cm) allowed for adequate sward recovery, favoring canopy structure. These findings contribute to the development of grazing management strategies that balance animal productivity with the conservation of the forage resource.