Effects of monensin on growth performance of beef heifers consuming warm-season perennial grass and supplemented with sugarcane molasses

• Published in: Tropical animal health and production 2019-02, Vol.51 (2), p.339-344
• Main Authors: Moriel, Philipe, Vendramini, Joao M. B., Carnelos, Caio, Piccolo, Matheus B., da Silva, Hiran M.
• Format: Article
• Language: English
• Subjects: Beef; Biomedical and Life Sciences; Cattle; Cottonseed meal; Data collection; Digestibility; Forage; Grasses; Insulin-like growth factor I; Life Sciences; Molasses; Monensin; Nutritive value; Pasture; Pastures; Regular Articles; Seasons; Sugarcane; Supplements; Veterinary Medicine/Veterinary Science; Zoology
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-018-1693-5

The objective of this study was to evaluate the effects of monensin on performance of beef heifers fed warm-season forages. Brangus heifers ( n  = 24) were stratified by BW and BCS, and randomly assigned into 1 of 12 bahiagrass pastures (1.2 ha and 2 heifers/pasture). Heifers were offered 14 kg of sugarcane molasses and 3.5 kg of cottonseed meal weekly from day 0 to 84. Treatments were randomly assigned to pastures (6 pastures/treatment) and consisted of heifers supplemented with or without 200 mg/day of monensin. On d 85, heifers were allocated to individual drylot pens, provided free choice access to bermudagrass hay, and received their respective treatment for 10 d of adaptation and 11 d of data collection. Monensin did not impact ( P  ≥ 0.13) heifer BW, BCS, overall ADG, bahiagrass IVDOM, CP, herbage mass, and allowance. Supplement disappearance after 10 and 34 h of supplementation was greater for control vs. monensin heifers ( P  = 0.04) and tended to be greater for control vs. monensin heifers 24 h post-supplementation ( P  = 0.07). Plasma concentrations of glucose, IGF-1, and BUN ( P  ≥ 0.24) did not differ between treatments. From d 85 to 106, forage and total DM intake, in vivo DM digestibility, and heifer growth performance did not differ between treatments ( P  ≥ 0.12). Therefore, adding monensin to sugarcane molasses-based supplements decreased supplement consumption rate, but did not impact growth and blood parameters of heifers grazing warm-season grasses with limited nutritive value.