Stockpiled Tifton 85 bermudagrass for backgrounding stocker cattle

Abstract

A 2-yr grazing trial was conducted to evaluate the use of conserved forage type, stockpiled Tifton 85 bermudagrass (Cynodon dactylon L.; T85) or T85 hay, and supplement type for stocker cattle during the fall forage deficit in the southeastern United States. The study site consisted of six 0.75-ha paddocks of stockpiled T85 for grazing and six 0.20-ha drylot paddocks for feeding T85 hay. Steers (n = 5 per paddock; mean initial BW for both yr, 263 ± 30 kg) were randomly assigned to paddocks on November 11, 2014 and October 28, 2015 in yr 1 and yr 2, respectively. Treatments included T85 hay or stockpile (control), T85 hay or stockpile plus 0.2 kg cottonseed meal and 0.7 kg soybean hulls∙steer-1∙d-1 (SUPPL1), or 0.45 kg cottonseed meal and 0.45 kg soybean hulls∙steer-1∙d-1 (SUPPL2). Polytape fencing was used for frontal grazing stockpiled T85 paddocks to allocate a 3-to 4-d allotment of forage DM for the animals based on available forage mass and steer DMI requirements. There were no differences among treatments (P > 0.10) in mean pregrazing forage mass across sampling dates (5,099 kg DM/ha and 7,998 kg DM/ha in yr 1 and yr 2, respectively), forage allowance (1.9 kg DM/kg steer BW and 3.0 kg DM/kg steer BW in yr 1 and yr 2, respectively) and forage utilization (84% and 88% in yr 1 and yr 2, respectively). No differences (P > 0.10) were detected for nutritive value parameters CP, ADF, NDF, and TDN among stockpiled T85 treatments in both yr. However, there were differences across sampling dates (P < 0.0001) for stockpiled T85 such that forage quality generally declined as the grazing season progressed in both yr. Steers fed T85 hay had greater final BW and ADG (P = 0.018) than those grazing stockpiled T85. Mean final BW and ADG of steers grazing T85 stockpile or fed hay with no supplementation was less (P = 0.020) than those receiving supplementation. Steers grazing stockpiled T85 had decreased ADG in the second half of the grazing season in both yr of the study, which is a result of declining forage nutritive value as the stockpiling season progressed. Results indicate that stockpiled T85 supplemented with CP and energy can support stocker cattle at a maintenance level, but to achieve a target gain of 0.9 kg/day would require a greater level of supplementation to overcome decreasing forage nutritive value dynamics.