2011 Annual Report
Information is being obtained on the quality and utilization of four subtropical grasses and two cool-season grasses and the associated plant-animal factors that alter their conversion to value added animal products. Grazing Trials: One trial (3 years) compared the animal and pasture productivity of endophyte-free 'Au-Triumph' tall fescue when three management strategies were stocked to effect efficient herbage utilization relative to average daily gain and steer gain ha-1. The second trial (2 years) evaluated per animal and per ha productivity of flaccidgrass when stocked over a range of three forage mass (FM) levels to determine the influence of FM on digesta kinetics and dry matter intake (DMI) of steers (data in press). Findings: During spring (about 70% of seasonal production) endophyte-free tall fescue continuously stocked (CS) from April to July was compared with either a daily allowance (DA) or a lax (7 to 12d) rotation (LR). The FM was managed to average 2673 kg/ha for the CS and 3057 kg/ha at turn on and 2844 kg/ha residue for DA and 2851 kg/ha at turn on and 2559 kg/ha residue for LR. Steer daily gain, stocking rate gain and effective feed units/ha were not altered by management strategy averaging 0.95 kg/day, 6.7 steers/ha, 585 kg/ha, and effective feed units of 3111 kg/ha. Furthermore, canopies wer similar averaging 54.9% leaf, 32.6% dead, 11.9% stem and 0.5% hears. Tall fescue can be managed flexibly to enhance animal production systems. 'Carostan' flaccidgrass was continuously stocked during the summer at increasing FM ranging from 1245 to 3585 k/ha with neither mean retention time nor passage rates of either liquid or digesta phases altered by FM. Fecal output increased linearly (P=0.04) from short to tall (0.643 to 0.739 kg/100 kg BW) indicating possible variation in dry matter intake (DMI). However, DMI and disgestible DMIs were similar in in-vitro dry matter disappearance (mean=713 g/kg) and neutral detergent fiber (mean=468 g/kg) regardless of FM. 'Carostan' flaccidgrass canopies were flexible and no optimum height was detected to optimize diet composition. This species has potential as a pasture species when properly managed. Stall Trials: Several intake and digestion trials to compare Caucasian bluestem (CBS) with Coastal and Tifton bermudagrasses, switchgrass, and big bluestem were conducted and summarized and published during fiscal year 2011. Findings: CBS was evaluated in four experiments and was readily consumed by steers whether cut as initial or regrowth hays.
Burns, J.C. 2011. Maturity and Regrowth Influences on Quality of Caucasian Bluestem Hay. Crop Science. 51:1840-1849. Burns, J.C., Fisher, D.S., Pond, K.R. 2011. Effects of Tall Fescue Forage Mass on Steer Ingestive Behavior and Performance. Crop Science. 51:1850-1864. Chavez, S.J., Huntington, G.B., Burns, J.C. 2011. Use of Plant Hydrocarbons as External Markers to Measure Voluntary Intake and Digestibility in Beef Steers. Journal of Animal Science. 139:245-251. Burns, J.C. 2011. Intake and Digestibility Among Caucasian Bluestem, Big Bluestem, and Switchgrass Compared with Bermudagrass. Crop Science. 51:2262-2275.