Recipient Organization
TEXAS A&M UNIVERSITY
750 AGRONOMY RD STE 2701
COLLEGE STATION,TX 77843-0001
Performing Department
Overton-TAMU Agr Res Cntr
Non Technical Summary
Forages supply approximately 70% of the nutrients consumed by the nearly $16 billion livestock and product industry in Texas (19). More than 90% of the feed supply in cow-calf operations and 60% in slaughter beef operations are derived from forages. Collectively, forages on pasture and rangeland occupy nearly 70% of the 130.5 million acres of land area in Texas. Much of this area includes land that is either marginally or completely unsuited for row crop production. Forages are therefore the primary crop in Texas that supports livestock, wildlife, and recreation as well as being an inseparable component of resource conservation and environment-sustainability. There is a research and implementation need for comparative information on forage varieties, sustainability, grazing systems, animal performance, and management strategies for pastures in Texas.Grasslands are complex, interdependent ecosystems influenced by the interactions of grazing animals, plants, soils, microorganisms, and climatic conditions (13). Grazing management strategies result primarily from long-term experience, and from grazing experiments targeted at defining input-output relationships. In a review, Sollenberger et al. (46) cited more than 460 articles to assess whether or not USDA-NRCS prescribed grazing practices on pastures met the purposes and criteria stated in policy guidelines. They identified the following primary purposes or desired outcomes from imposing management strategies: 1) grazing intensity (stocking rate); 2) stocking method (continuous vs rotational); 3) timing of grazing (season of grazing and deferment from grazing); 4) type and class of livestock used; and 5) livestock distribution on landscape. These management strategies significantly influence resource conservation and ecosystem sustainability. The inclusion of the livestock component in sustainable agricultural systems provides for greater opportunities to evaluate forage utilization, soil fertility, and nutrient cycling (16, 17, 38). Long-term field research is critically necessary to provide information on sustained agricultural systems that involve the complex interactions of soils, plants, animals, climate, and management (18, 30, 45, 50).The primary purposes of this research are to evaluate forages and forage-animal stocking systems under component methodology. Thus, a hierarchical method of experimentation will progress from evaluation of forages under defoliation regimens without an intent to monitor animal performance to pasture-sized experiments to quantify utilization systems and effects on animal performance. With existing pasture facilities and animal numbers, the intent and flexibility to retain ownership from birth to harvest provides an excellent opportunity to maximize biological databases (27). Special attention has been given in previous experiments to defining long-term stocking effects on soil-plant parameters and nutrient cycling (31, 33, 39, 40). The research objectives that follow outline the protocol involved with the progression of exclusive plant evaluations to soil-plant-animal evaluations to mathematical descriptions of forage-animal production systems.
Animal Health Component
75%
Research Effort Categories
Basic
25%
Applied
75%
Developmental
(N/A)
Goals / Objectives
1. Evaluate forage germplasm and cultivars for dry matter production, nutritive value, persistence, and sustainability under various defoliation regimens.2. Ascertain the impact of stocking rate and fertilization regimens on soil nutrient status, forage stand maintenance, biodiversity of forages, and nutrient cycling in bermudagrass pastures.3. Quantify the effects of stocking strategies, stocking methods, and forage utilization systems on pasture and animal performance parameters from birth-to-harvest.4. Describe biological efficiencies via modeling and project economic implications of production systems using forage-animal interface database.
Project Methods
Objective 1: Germplasm and cultivars of forages including, annual ryegrass, clovers, small grains, cowpeas, lablab, and alfalfa will be grown in replicated plot-sized areas and/or pasture units. Seasonal and total dry matter production and nutritive value will be assessed on forage defoliated at different regimens of height and frequency. Plot-sized areas of cowpeas, and lablabs will be harvested via mechanical, power-driven sickle-bar mower. Cultivars of cowpea and lablab will be evaluated for nematode resistance, N-fixation and transfer, biomass, and seed yield (23). An existing herd of F-1 cows (Hereford x Brahman) and their Simmental-sired calves will be used to defoliate pastures or plots to various levels of forage mass. Continuous and/or rotational stocking will be used to assess forage persistence and regrowth of bermudagrass, and cool-season annual forages (29). Animal performance, grazing behavior, and pasture utilization data will be collected. Forage parameters to be measured include mass, vigor, stand maintenance, and nutritive value. Forages will be assayed for protein, fiber components, and digestibility using accepted wet chemistry techniques (15, 20, 22, 43). Nutritive value parameters that affect animal performance and/or lignocellulose content for bioenergy alternatives will be quantified. Statistical procedures of SAS will be used for the completely randomized and randomized complete block designs. Principal procedures will include PROC MIXED and PROC GLIMMIX.Objective 2: Pastures of both common and 'Coastal' bermudagrass are available which have been grazed at three different stocking rates since 1969 (12). This unique, long-term stocked pasture area offers excellent opportunities to quantify the impact of recycled plant nutrients under stocking conditions (31, 38, 39, 40). At each of three levels of forage mass (stocking rates) for both bermudagrasses, overseeding x fertility treatments will include: (a) ryegrass plus N fertilizer split-applied during the ryegrass-bermudagrass growing phase (season total of 150 to 250 kg N/ha); and (b) clover without N fertilizer. All pastures will receive identical rates of P2O5 and K2O. Soil nutrient status (pH, N, P, K, etc) carbon (42, 51), soil compaction, root-rhizome density, forage mass, stand maintenance and density, vigor, species diversity and composition, and animal performance per animal and per unit land area will be quantified. Cows and calves from two calving seasons will graze the overseeded bermudagrass pastures from February to mid-June (fall calves) and from mid-June to early October (winter calves). At 28-day intervals, animals will be weighed and visual body condition scored. On each stocking rate x fertility treatment, forage mass and forage allowance (34, 35, 44) will be maintained as uniformly as possible, using variable stocking rates, between the ryegrass + N and the clover without N treatment pastures (36). Forage in quadrats will be clipped to ground level from at least 4 sites on each 0.5 to 1.0 ha pastures at 28-day intervals. Forage for nutritive analyses will be taken at 14-day intervals by hand-plucking plant parts that visually represent that selected by the grazing animal. Nutritive value will be assessed via wet chemistry techniques to quantify protein, fiber components, digestibility, etc (15, 20, 48). Grazing distribution (patch grazing), forage utilization, and animal excreta patterns will be monitored. Forage-animal performance from these grazed areas will be subsequently used as reference points for pasture fertilization recommendations for Coastal Plain soils. Each pasture will be blocked into 10 sub-plots for taking soil samples to various depths, assessment of forage stand, and species diversity. Two qualified people will make independent visual scores in each sub-plot to quantify forage composition and species diversity (37). Plant samples collected from stocking rate x fertility regimen pastures will be compared with adjacent bermudagrass pastures which have not been subjected to stocking treatments and are deemed to have the same as the original bermudagrass stand. This experiment will be analyzed via SAS procedures using PROC MIXED to account for: Year, Season within Year, Bermudagrass, Fertility Regimen, and Stocking Rate. Forage quality indicators, ADG of calves and cows as well as gain per acre will be compared among treatments.Objective 3: At weaning, calves previously raised during lactation on various stocking rate pastures will be weaned and grazed on Tifton 85 and Coastal bermudagrass (fall calves), or small grain-ryegrass (winter calves). During the stocker period, calves will be subjected to treatments of stocking strategies, stocking method, stocking rates, and/or supplementation (27, 28). Pastures will each be grazed at three or more stocking rates to assess forage allowance impact on animal performance. Forage parameters to be taken include mass, nutritive value, stubble height, and pasture utilization (grazing distribution). A visual, pasture-condition scoring method will be employed to serve as a potential technology transfer technique for those making grazing management decisions. Weight gain and condition scores of stocker calves will be collected at 28-day intervals and subsequent calculations of gain per animal and gain per hectare relationships will be conducted. After the stocker period, all yearlings will be transported to either a research feedlot facility or a commercial feedlot. At the end of the feeding period, cattle will be harvested at a research or commercial packing facility, and a broad array of physical and sensory carcass characteristics will be taken. Lifetime performance of animals and stocking strategies will be used for both segmented and life-time performance parameters (27, 32). Statistical procedures of SAS, primarily PROC MIXED and PROC GLIMMIX, will be used to assess potential relationships between previous forage treatment, feedlot performance, and carcass traits (2). Growth rate of calves will be assessed from various pasture systems using covariate and regression analyses to detect influence of previous treatment(s) on feedlot performance and carcass traits.Objective 4: Data collected from the previously-listed objectives as well as data from previous years' research from selected long-term stocking areas will have significant implications for management strategies of sustained pasture-animal production (33, 35). Use of these data to develop mathematical expressions for decision aids, management choices, expert systems, research initiatives, etc. will impact the biological-economic factors of forage-animal systems. The implementation of this objective will include cooperative relationships with statisticians, agricultural economists, plant physiologists, and animal nutritionists. It will also involve others who have expertise in the transformation of biological parameters into existing and new models for use by professionals and producers interested in sustained, economic production of forage-based systems for livestock or resource conservation. Efficiency of production parameters on pastures will impact environmental aspects and risks associated with management strategies. Existing and new models for using forage and/or animal production functions in decision aids, expert systems, etc. will accommodate plant-animal data from these trials.