Submitted to: Rangeland Ecology and Management
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/14/2006
Publication Date: 1/3/2007
Citation: Arthington, J.D., Roka, F.M., Mullahey, J.J., Coleman, S.W., Lollis, L.O., Muchovej, R.M., Hitchcock, D. 2007. Integrating ranch forage production, cattle performance and economics in ranch management systems for south florida. Rangeland Ecology and Management. 60(1):12-18. Interpretive Summary: One of the most critical regions for addressing sustainable management of grazing systems is south central Florida, where extensive subtropical range and pasturelands intersect with some of the most sensitive natural systems in the United States. In this region, most of the cattle production occurs on vast areas of rangeland and improved pasture. The region in environmentally important by supporting a rich diversity of plant and animal habitat and is home to a number of endangered species. Lake Okeechobee, the receiving water body in the region, is threatened by increased phosphorus inputs. It has been assumed that due to the vast acres devoted to cattle operations, those operations contribute significantly to the eutrification of the waterways and the lake. A broad-based partnership including the University of Florida, the Archbold Biological Station, the South Florida Water Management District, The USDA, ARS, STARS, and the Florida Cattlemen's Association, has been formed to increase understanding of the interrelationships among commercial livestock, native range flora and fauna, nutrient cycling soil microorganisms, and surface water quality on a working ranch. A series of eight improved bahiagrass pastures were grazed during the summer (May-October) and eight native pastures were grazed in winter (October to May) by mature pregnant crossbred cows and their subsequent calves, which were born in October to December each year. Treatments included 0, 1.4, 2,5 and 3.3 acres/cow for the summer pastures (50 acres ea) and 0, 2.3, 4.0, and 5.3 acres/cow for winter pastures (80 acres ea.). From other portions of the project, it was found that neither the presence of cattle (control vs. treatments) nor stocking density had any impact on water quality, bird density, or soil microbial populations. The goals of this phase of the project were to determine if increased stocking density had an impact on animal performance, forage quality, and profitability of the ranching enterprise. Body condition score of cows were affected by stocking density only when the cows were removed from the winter (native) pastures during lactation. Calf weaning weights were not affected, but profitability was increased with increased stocking density because more beef was harvested to offset fixed costs.
Technical Abstract: Decreasing cattle stocking densities is one practice that has been suggested to improve surface runoff quality draining into Lake Okeechobee, Florida. A holistic approach is needed to address both production and economic implications associated with lower animal densities. The objective of this study was to determine the effects of stocking rate on cow-calf performance, available forage and quality, and the ranch's financial position. Experimental pastures have been established on a typical south Florida cow-calf operation. Stocking rates of 0.58, 1.01, and 1.35 ha cow-1 on summer pastures and 0.93, 1.62, and 2.16 ha cow-1 on winter pastures corresponded to high, medium, and low rates, respectively. Cow body condition scores, pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside grazing exclusion cages and the available forage outside the cage. Crude protein, in vitro organic matter digestibility, and phosphorus concentration were used to estimate forage quality. Partial budgeting was used to estimate economic implications of reduced stocking rates. Forage yield, utilization, and quality were not significantly affected by stocking rate. While cattle in the medium and high stocking rates had lower body condition scores following the winter grazing period, no significant impacts were verified on pregnancy rate and calf gains. Production, as measured by kilograms of calf weaned ha-1 of dedicated land was improved (P<0.01) for high compared with medium and low stocking rates. Overall ranch profitability decreases as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch's fixed cost structure.