Effects of Stocking Rate On "Jiggs" Bermudagrass Forage Characteristics and Animal Performance.

There is increasing interest in ‘Jiggs’ bermudagrass (Cynodon dactylon L.) for grazing systems in South Florida, primarily because of its greater tolerance to poorly drained soils.  However, there is limited information available about Jiggs grazing management.  The objective of this study was to test the effect of different stocking rates on animal performance and herbage characteristics of Jiggs pastures. The experiment was conducted at the UF/IFAS Range Cattle Research and Education Center – Ona, FL from May to September 2011. Treatments were three stocking rates (SR) [2 (low), 5 (medium), and 8 (high) calves liveweight (LW) = 199±30 kg ha^-1], in a randomized incomplete block design. Pastures were 0.25 ha stocked continuously using a fixed stocking rate. Calves were supplemented with 1% BW concentrate [140 g kg^-1 crude protein (CP) and 780 g kg^-1 total digestible nutrients (TDN)] during the experimental period. Calf weight was recorded every 28-d and used to calculate average daily gain (ADG). Herbage parameters were measured every 14 d. There was a linear (P < 0.05) decrease in herbage mass (from 2.8 to 1.7 Mg ha^-1), light interception (from 95 to 87%), forage height (from 35 to 22 cm), in vitro digestible organic matter concentration (from 560 to 480 g kg^-1), and herbage allowance (from 1.8 to 0.3 kg DM kg^-1 LW) with increasing SR. However, there was no effect of SR on herbage accumulation rate (Mean = 58 kg ha^-1 d^-1) and CP concentration (Mean = 165 g kg^-1). Calf’ ADG and gain per ha were negatively affected by increasing SR and decreased from 0.63 to 0.30 kg d^-1 and from 1300 to 700 kg ha^-1 for ADG and gain per ha, respectively. The grazing stubble height of Jiggs affects ADG and gain per ha and the target stubble height may be dependent upon the objectives of the manager. Long-term studies are necessary to verify the persistence of Jiggs under greater stocking rate and shorter stubble height.