Alternative Forage Systems for Developing Replacement Heifers
Marks, Marty Landon
Type of DegreePhD Dissertation
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Heifer development systems are an essential phase of beef production due to lifelong production implications. Reproductive success of a heifer’s first breeding season is critical to the sustainability of cow-calf production systems. Understanding the effects that different management practices have on a heifer’s ability to conceive to artificial insemination or a clean-up bull are essential to the sustainability of beef cattle production systems. Cattle producers experiencing increased costs might consider alternative heifer development strategies without sacrificing growth or pregnancy rates. Heifer development systems utilizing grazed forage systems could be an option for some producers. Understanding the impacts of different forage species and mixtures could help provide a lower input method of developing heifers in these systems. The objective of this dissertation was to evaluate alternative forage systems for developing replacement heifers. A multi-year heifer development demonstration project at the Sand Mountain Research and Extension Center in Crossville, AL supported local beef heifer development using cool-season annuals, and provided 13 consignors with herd production data that can be used to further herd potential over time. Integration of legumes into warm-season grasses is an important step in producing a better quality forage with less N inputs as a potential grazing option for developing heifers. Fall-planting of alfalfa into bermudagrass systems may better favor production and persistence characteristics of mixed stands compared with spring plantings, where a spring-planted mixture of ‘Bulldog 505’ alfalfa and ‘Tifton 44’ bermudagrass sustained a less than 20% contribution from alfalfa in the year-after-planting. Summer perennial forage systems, such as native warm-season grasses or bahiagrass, may support heifer growth during the summer months prior to winter breeding for fall-born calves; however, growth rate of heifers may be relatively slow during this time period (0.4 to 0.7 kg/day). For the metabolomics analysis, this limited number (n = 27) animal project, differences were not observed between heifers conceived to AI vs. natural conception to clean-up bull and no differences were observed across forage treatments. These projects demonstrate that using alternative forage options such as cool-season annuals, legumes in warm-season forage systems, and native species may diversify systems management options for beef producers evaluating heifer development strategies on-farm.
- Dissertation (Final Version).pdf