Location: Forage and Livestock Production Research
Project Number: 3070-31630-006-00-D
Project Type: In-House Appropriated
Start Date: Oct 1, 2012
End Date: Sep 30, 2017
The long-term objective is to improve understanding of forage-based production systems and genetics that allow ruminant livestock to efficiently consume and convert feedstuffs, primarily forages, in profitable production systems while mitigating negative impacts on the environment. Specifically, during the next five years we will focus on the following objectives. Objective 1: Determine how forage livestock production systems interact with plants, soils, and climate with respect to carbon and nitrogen cycling under forage and grazing systems typical for the southern plains. Sub-objective 1A: Evaluate continuous and management intensive rotational grazing systems on native prairie pastures and quantify cow-calf production traits, animal and plant productivity, input requirements, and carbon (C) and nitrogen (N) dynamics in the soil-plant-animal-atmosphere continuum. Sub-objective 1B: Determine greenhouse gas (GHG) emissions from soil, plant, and animal components of diverse grazing systems. Objective 2: Determine the most efficient ruminant genetic types for forage-based production systems to optimize forage use efficiency. Sub-objective 2A: Determine how frame score affects calf growth rate, carcass quality, and economic returns under different finishing systems. Sub-objective 2B: Evaluate growing and finishing systems for impact on growth rate, carcass quality, and economic returns for sheep of different genetic types. Objective 3: Evaluate feed intake and nutrient use efficiency of beef cattle fed diets varying in proportions of forage and grain in varying environments. Sub-objective 3A: Determine the effect of frame score on intake and feed efficiency of growing cattle in different seasons. Sub-objective 3B: Determine the effect of frame score and dietary metabolizable energy density on intake and feed efficiency of mature cows. Sub-objective 3C: Determine intake, diet nutritive value, and growth rate of stocker calves grazing cool-season annual and perennial forages. Objective 4: Improve breeding and management decisions by characterizing current genetic and phenotypic variation within and between predominant beef breeds and crosses using novel genomic and genetic evaluation technologies and identify novel genomic variants to optimize forage based production efficiencies for beef cattle within and across diverse physical environments in the US Great Plains.
The research will focus on improving production efficiency while mitigating the environmental impact of forage-livestock systems by matching animal genetic type to the proper production and nutritional regime. For objective 1), two farm-scale replicates of two grazing systems on tallgrass prairie are used to evaluate the long-term impacts of grazing system on input costs, animal performance, rangeland health, soil ecological function, and plant diversity. Grazing systems consist of continuously and rotationally grazed under an adaptive management framework. Animal production, forage biomass and species diversity will be monitored. Angus:Brahman F1 cows bred to Charolais bulls will constitute the grazing cow herd. Greenhouse gas (GHG) emissions will be monitored on: 1) native tallgrass prairie and 2) wheat pasture. Eddy covariance flux towers will be established in each pasture type to calculate CH4, CO2, water, and energy fluxes. Cattle position will be monitored using global positioning devices. Differences in GHG production with and without cattle will be determined. Simultaneously, forage intake, diet digestibility, and methane emissions will be determined using marker systems on a select group of individual animals to assess components of efficiency at the animal scale. Under objective 2, research will be conducted to match finishing system with cattle genetics to optimize biological, economic, and ecological efficiency. Frame score, associated with rate of maturity and reproductive efficiency, will be used to characterize different genetic types. At weaning, calves from each frame score class will be assigned to one of two postweaning treatments: 1) conventional (wheat pasture followed by feedlot), and 2) extended forage followed by a short feedlot phase (30-50 days) if needed]. When finished, calves will be harvested; carcass data, Warner-Bratzler shear, sensory by a trained panel, and fatty acid profile will be determined. Under objective 3, all replacement heifers, and some companion steer herd mates, will be evaluated for feed efficiency at weaning. They will be fed forage-based diets to achieve 1 kg/d gain, and individual daily intake and weight gain will be recorded. After the heifers reach maturity they will again be evaluated as mature, non-lactating cows (5 years of age). Cows will be fed a ration based on Bermudagrass baleage at maintenance for 84 d, weighed at 14-d intervals, and after final body weights are recorded on day 84, offered ad libitum access to the same ration. Efficiency will be determined as the difference in requirements and feed consumed and related to productivity during the first four calf crops. Under objective 4, research will be coordinated with the Range and Livestock Unit at Miles City, MT, and the Genetics, Breeding, and Animal Health Research Unit at Clay Center, NE. Sample collection and analysis protocols will be developed collaboratively. Novel genomic approaches will be used to enhance knowledge of the bovine genome, improve genetic merit of purebred and crossbred beef cattle, and improve beef cow energetic efficiency, especially related to grazing and high forage based diets.