Location: Forage and Livestock Production Research2012 Annual Report
1a. Objectives (from AD-416):
The long-term objective of this project is to determine the feasibility of producing grass-fed beef in the Southern Great Plains and resolve the major constraints to finishing cattle on forages. If it is not possible to produce beef with 100% forage inputs, then we will develop systems that utilize more forage inputs to lessen our dependence on feed grains, increase revenues to local rural communities and small farmers, and produce more beef under free range conditions that appeal to the socially conscious consumer. In some cases, we will use sheep as a ruminant model to rank forages based on nutritional qualities, determine the impact of dietary supplementations on forage digestibility and protein metabolism, and the effect of genetics on forage intake and utilization. Over the next 5 years we will focus on the following specific objectives: Objective 1: Design, install, and evaluate, year-long forage-based livestock production systems that include multiple forage species to fill the forage deficit gaps in the spring and fall. Sub-objective 1.A. Develop year-long forage-based livestock production systems utilizing perennial cool-season forages and annual and perennial warm-season forages. Sub-objective 1.B. Determine the most efficient combination of beef cattle genotypes and forage-based production systems. Sub-objective 1.C. Determine the impact of maternal influence on postweaning performance of cross-bred calves from two-breed cross cows where calves are managed under two postweaning systems to enhance the efficiency of finishing cattle on pasture. Objective 2: Define and develop management strategies to mitigate nutrient imbalances that limit the production of grass-fed beef by year-round grazing systems developed for the southern Great Plains. Sub-objective 2.A. Compare the digestibility and N utilization of perennial cool-season grass species that may be used to fill-in the forage deficit gaps in a multiple forage species production system used to produce grass-fed beef. Sub-objective 2.B. Determine if energy or protein limits average daily gain (ADG) of calves grazing warm- and cool-season grasses under short-duration intensive-stocking management as part of a system to produce grass-fed beef. Sub-objective 2.C. Determine low-cost supplementation for stockers grazing cool-season and warm-season forages to approach genetic potential for postweaning stocker gains in purebred and crossbred stocker lambs. Sub-objective 2.D. Develop methodology to determine forage intake using forage canopy spectral reflectance and evaluate genetic effects for forage intake and efficiency of forage utilization.
1b. Approach (from AD-416):
Stocker calves of different breed types will be used to determine the interaction between breed type and intensity of livestock management on the rate and efficiency of body weight gain. Combinations of warm- and cool-season forage resources will be evaluated as components of a year-round grazing system. Nutrient imbalances that limit efficiency of beef production on pasture will be identified and management practices to mitigate these imbalances will be developed. New methodology to determine nutrient intake of grazing animals will be developed to give pasture managers a new tool to aid in their decision making process.
3. Progress Report:
Field work for evaluating combinations of beef cattle genotypes and forage-based productions systems were completed. Additional Angus cows of different genetic types and smaller frame score were obtained from the Brooksville, FL, station to complement the industry standard Angus that had been purchased. Postweaning and carcass data was collected on the 2010 calf crop produced from 6 cow breed groups managed under two preweaning management systems and two postweaning management systems. Even with extreme drought conditions during the 2011 growing season, all of the finished cattle graded select or better, even the forage finished steers. The project evaluating the impact of maternal influence on postweaning performance was completed with milk production and quality measurements taken in the six cow breeds to provide more basic information in interpretation of milk yield and quality on postweaning performance. An intake trial on pasture was initiated to determine the cause of reduced gains of stocker cattle grazing cool-season perennials as compared to winter wheat. Laboratory analysis, and a second year of field trials will continue into the next year. A new project has been prepared, evaluated and certified to begin in FY13.
1. Tropically adapted steers have reduced rate of gain during the winter. Cattle in the southeastern and Gulf Coast region of the U.S.A. are impacted by heat, humidity, parasite and disease exposure Brahman and particularly F1 Brahman x English cows have proved to be ideal brood cows for the subtropics, but their calves are often discounted because of perceptions for poor performance and efficiency during finishing, particularly in temperate environments. Tropically adapted B. taurus breeds of cattle such as the the Criollo breeds from Central and South America may offer sufficient adaptation as alternatives to or in combination with the Brahman for cow-calf production in the Gulf Coast region. ARS scientists in Brooksville, Florida, and El Reno, Oklahoma, collaborated to evaluate the Criollo breed, Romosinuano, from South America as purebreds and F1 crosses with Brahman and Angus during the postweaning growth and finishing phases of production. Tropically adapted Brahman and Romosinuano and their crosses were heavier than Angus and their crosses at weaning in Florida, but gained more slowly in Oklahoma during the winter while grazing wheat pasture. During the finishing phase beginning in May each year, gains were not different among breed types. Heterosis (hybrid vigor) for gain and weight were almost twice as great for Brahman-Angus crosses as for the other crosses. However, we did not find evidence for heterosis for feed efficiency among any crosses. These data would suggest that tropically adapted cattle should be wintered in more southerly climates before finishing in temperate zones.
Blackburn, H.D., Toishibekov, Y., Toishibekov, M., Welsh, C.S., Spiller, S.F., Brown, M.A., Pavia, S. 2011. Genetic diversity of Ovis aries populations near domestication centers and in the new world. Genetica. 139:1169-1178.