Stocking method and monensin supplementation effects on cow and calf performance and pasture productivity

Abstract

In the northeastern United States, pastures are predominantly cool-season perennial grasses and legumes that are dormant in the summer resulting in a decline in forage nutritive value and availability, commonly referred to as "summer slump." Strategies to alleviate summer slump may include stocking management or supplementation with or without an ionophore such as monensin to maximize efficiency. A 3-yr study (n = 32 cow-calf pairs; 718.0 ± of 83.9 kg) was conducted to evaluate the effects of rotational (ROT) or continuous (CONT) stocking method with or without monensin on forage production, pasture nutritive value, and animal production. Continuous and ROT stocking treatments were assigned to eight 2.9-ha pastures with two replicates/year for 56 grazing days during the summer. Treatments were arranged as a 2 × 2 factorial, and supplements included with or without monensin (200 mg cow −1 daily; Rumensin 90, Elanco Animal Health) delivered once daily (0.45 kg cow −1 ). Disk meter height was maintained using put-and-take animals with four tester cow-calf pairs per pasture. Carrying capacity (CC) and calf average daily gain (ADG) were not influenced by stocking management. Rotational stocking increased cow body weight (BW) change by 6.6 kg. Monensin improved CC by 9% regardless of stocking method but did not affect cow BW change or calf ADG. Based on this study, monensin can improve carrying capacity and stocking rate regardless of stocking method. Implementing rotational stocking may improve pasture health by suppressing weed growth and enhancing forage nutritive value in pastures containing cool-season perennial forages.