Grev, Amanda2019-03-132019-03-132018-12https://hdl.handle.net/11299/202194University of Minnesota Ph.D. dissertation. 2018. Major: Animal Sciences. Advisor: Krishona Martinson. 1 computer file (PDF); 182 pages.Although alfalfa is a preferred forage source for horses and other herbivores with advanced dietary requirements, the digestibility and utilization of alfalfa by these animals is hampered by its lignin content. Populations of reduced lignin alfalfa are now available, and research with these experimental populations has shown their potential to improve forage quality and digestibility. However, field evaluations under diverse conditions are needed to determine the performance of new commercial alfalfa cultivars containing the reduced lignin trait, especially with regard to forage accumulation and nutritive value under different harvest frequencies. To evaluate the effects of varied harvest frequencies and changing forage maturity on yield, quality, and stem and leaf characteristics for reduced lignin alfalfa, two field studies were completed. The objectives of the first study were to evaluate forage accumulation and forage nutritive value for reduced lignin and reference alfalfa cultivars when subject to diverse cutting treatments during the establishment and first production year. The objectives of the second study were to characterize changes in morphological development and forage nutritive value within leaf and stem fractions for reduced lignin and reference alfalfa cultivars over time. In addition to the need for an evaluation of the performance of reduced lignin alfalfa cultivars in the field, it remains to be seen if the improvements in in vitro DMD and NDFD for reduced lignin alfalfa will translate to greater in vivo digestibility when fed to the animal directly. A variety of methods have been successfully used to evaluate digestibility and related nutritional parameters, including fecal particle size and digesta passage rates. While preliminary information surrounding the forage nutritive value and digestibility of reduced lignin alfalfa is promising, information on forage digestibility for current, commercially available reduced lignin alfalfa cultivars is not yet available, and digestibility changes have not yet been evaluated in the equine model. Therefore, a digestibility study in which reduced lignin and reference alfalfa hays were fed to horses was completed. The objectives for the study were to evaluate apparent digestibility and other digestibility-related parameters, including fecal particle size and retention time, when feeding reduced lignin and reference alfalfa hays to adult horses.enThesis or Dissertation