Rangelands in the Campos region of South America managed as stockpiled forage: impacts on intake, digestibility, nitrogen-use efficiency, and methane emissions in sheep

Stockpiling forage is the practice of deferring grazing to allow forage accumulation in the field for use later during periods of limited pasture growth. Whereas stockpiling forage from rangeland offers a cost-effective strategy for grazing ruminants in the Campos region of South America, identifying the optimal duration of the stockpiling period remains a challenge. This study evaluated key nutritional parameters, including forage nutritive value, intake, nitrogen (N)-use efficiency, and methane (CH4) emissions in sheep fed stockpiled forage from native rangeland accumulated under varying growing degree-days (GDD) thresholds. The study used forage from a native rangeland in Uruguay, stockpiled between October 2020 and February 2021 under four GDD accumulation thresholds (1000, 1500, 2000, and 2500). Sixteen 18-month-old Corriedale wethers (46.2 ± 2.8 kg body weight) were fed ad libitum in a feeding trial conducted in individual metabolism cages over two periods (n = 32). Although GDD thresholds affected the sward structure, forage chemical composition was unaffected in this study. Nutritional parameters, including nutrient intake, digestibility, N-use efficiency, and CH4 emissions in sheep fed stockpiled native rangeland forage accumulated under varying GDD thresholds, were also unaffected in this study. Managing multi-species native rangeland as stockpiled forage in the Campos region, with pre-stockpiling mowing and up to 2500 GDD thresholds during the warm season, does not affect forage chemical composition, nutrient intake and digestibility, ruminal parameters, N-use efficiency, or CH4 emissions in sheep. In practical terms, stockpiling thresholds from 1000 to 2500 GDD during the warm season (November to February) correspond to approximately 30–115 days, represent a wide window of thermal sums and time to efficiently accumulate forage in this type of rangeland without impairing sheep nutrition.