Location: Forage and Livestock Production Research2017 Annual Report
1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
Three barns used for beef cattle research were destroyed in May 2011 by a tornado. One research barn was repaired in 2012 and an area retro-fitted in 2017 to provide office and laboratory space for the new Veterinary Medical Officer. A second barn was replaced, retro-fitted with a Calan Gate Feeding System in 2012-2015. It was used to determine feed intake and feed efficiency by beef cattle. A third barn was replaced and is currently being installed with a GrowSafe Cattle Feeding System which uses advanced technology to collect research data related to feed intake and feed efficiency. Pasture-based systems using various forages for backgrounding and finishing beef cattle were evaluated (Objective 1). Included was a systems-level (soil-plant-animal) study of grazed agro-ecosystems evaluating responses of forage quality of sorghum-sudangrass pasture supplied N from cool-season forage green manures, soil properties, water balance, and animal performance (currently in the fifth year of data collection). Canola was evaluated to determine its suitability as grazing crop for stocker cattle during winter months (Objective 2). Soil type and seeding rate did not impact canola dry matter forage production during the fall growing season. Twenty acres of canola provided 930 grazing days for 500-pound heifers from mid-November until late-December. The growing heifers averaged 1.5 pounds per day gain during that period. Weight gain, carcass parameters, and meat quality when beef cattle were finished on pasture was compared to beef cattle contemporary groups finished on high concentrate (corn diets) and high forage diets (Objective 2, Sub-objective 2A). During the finishing period, cattle on concentrate averaged 3.0 pounds per day gain while those finished on alfalfa pasture averaged 2.25 pounds per day gain. Across all finishing treatments, smaller framed cattle had average daily gains (ADG) of 2.3 pounds per day while larger framed cattle had 2.5 ADG. Larger frame cattle also had heavier carcasses, equating to more salable product per head. Frame size and finishing diet did not impact beef tenderness. Feed intake, rumination time, and weight gain were measured in beef heifers differing in frame size to better understand feed- and nutrient-use efficiency for identifying and selecting the type of beef animal more adapted to the production environment of the Southern Great Plains (Objective 3). Heifer frame size did not appear to influence feed efficiency on a forage diet (Objective 3, Sub-objective 3A). Rumination time does not appear to be related to feed efficiency, but may be related to genetic type. Enteric methane production from individual cows (large and small frame) was measured throughout the grazing season (Objective 1, Sub-objective 1B). In addition, periods of more intensified sampling of forage quality and determination of forage intake and methane production by cattle grazing native warm-season grassland during times of high forage quality (July), declining forage quality (October), and dormant forage quality (January) were completed to better understand enteric methane trends. Larger framed (LF) cows produce heavier calves than smaller framed (SF) while being maintained on Native Prairie pastures. During the summer and fall, LF cows emitted greater daily amounts of methane (CH4) and carbon dioxide (CO2) than SF cows. However, when expressed as unit of CH4 or CO2 per unit of weaned calf, there was no difference in CH4 or CO2 emissions due to size of cow. Both sizes of cows emitted greater amounts of CH4 and CO2 in summer than fall (Objective 1, Sub-objective 1B). Studies were completed to determine intake by beef steers grazing pastures of Jose tall wheat grass or winter wheat pastures to better understand differences in weight gains (Objective 3, Sub-objective 3C). A long-term agroecosystem research (LTAR) crop and livestock production-scale farm site was planned and established in 2012-2015 (Objective 1). The LTAR crop farm integrates winter wheat (for grain and grazing), canola (for grain), and beef cattle production for water, soil, plant, animal, and atmospheric research data collections (Objective1, Sub-objective 1B). Soil nutrient flux measurements were collected from two native prairie pastures sites managed with continuous, rotational, or mob grazing, or managed with yearly prescribed spring burning followed by various intensities of grazing by beef cattle to evaluate long-term effects on native grassland ecological parameters as part of an LTAR grazing project (Objective 1, Sub-objective 1A). A new collaborative research project plan was developed with the Genetics, Breeding, and Animal Health Research Unit at Clay Center, Nebraska and the Range and Livestock Unit at Miles City, Montana (Objective 4). This project integrated novel genomic approaches 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 in order to evaluate genetics x management x production environment interactions.
1. Grazing legume pastures helps reduce doses of dewormer needed for meat goats. A major challenge in pasture-based meat-goat production systems for improved economic production is control of gastrointestinal parasites. ARS scientists at El Reno, Oklahoma along with colleagues at Michigan State University, East Lansing, Michigan and Virginia Tech, Blacksburg, Virginia demonstrated that grazing red clover and birdsfoot trefoil had beneficial effects on improving weight gain and resilience to internal parasite infection, and reducing reliance on dewormers.
2. Genetic selection in beef cattle for resistance to horn flies. Annual economic losses to the U.S. beef cattle industry attributed to horn fly infestations are estimated to be in excess of $700 million. ARS scientists at El Reno, Oklahoma with along with colleagues at the University of Arkansas, Fayetteville, Arkansas demonstrated that using Hsp70 genotypes in beef cattle along with forage management can aid in identifying production systems that reduce horn-fly infestation and reduce reliance on pesticides.
Turner, C.M., Brown, Jr, H., Brown, M.A., Steelman, D., Rosenkrans, C. 2013. Associations among heat shock protein 70 genotype, forage system, and horn fly infestation of beef cattle. Journal of Animal Science. 29:237–241.
Zhou, Y., Xiao, X., Wagle, P., Bajgain, R., Mahan, H., Basara, J., Dong, J., Qin, Y., Zhang, G., Luo, Y., Gowda, P.H., Neel, J.P., Steiner, J.L., Starks, P.J. 2017. Examining the short-term impacts of diverse management practices on plant phenology and carbon fluxes of Old World bluestems pasture. Agricultural and Forest Meteorology. 237:60-70. https://doi.org/10.1016/j.agrformet.2017.01.018.