Evaluation of Rumen Degradation Kinetics of Low-Lignin Alfalfa ‘Hi-Gest(®) 360’ in Saskatchewan Canada

SIMPLE SUMMARY: Digestibility (or degradability) of alfalfa by animals is hampered by its indigestible type of fiber called lignin. Recently, Alforex Seeds (Woodland, CA, USA) released a low-lignin cultivar called Hi-Gest(®) 360. We studied degradability of ‘Hi-Gest(®)360’ in monoculture and binary mixtures. Two cultivars of alfalfa (Hi-Gest(®)360 and AC Grazeland) and their binary mixtures with hybrid bromegrass (cv. AC Success) were cut at three maturity stages of alfalfa (10%, 40%, and 100% bloom) and were incubated in cannulated cow’s rumen. Protein and fiber disappearances were calculated as the difference between original and residue amounts of alfalfa after ruminal incubation. Decline in degradability as maturity stage advanced in the forages was evident. The ‘Hi-Gest(®)360’ had 8.6% less lignin compared to AC Grazeland. The HiGest possessed an average of 13% greater fiber and 5% greater dry matter degradability relative to AC Grazeland. Moreover, ‘Hi-Gest(®)360’ maintained quality for a longer time. This finding indicated that delaying harvest of ‘Hi-Gest(®)360’ alfalfa by up to two weeks did not affect the digestibility of nutrients. Thus, the results suggest that if digestibility (or quality) of forage and wider harvest window and/or later harvest is the main concern for producers, then ‘Hi-Gest(®)360’ may be a better alternative among alfalfa cultivars. ABSTRACT: The objective of this study was to determine rumen degradation kinetics of new low-lignin alfalfa (Medicago sativa L.) cv. Hi-Gest(®)360 (HiGest) in comparison with conventional alfalfa cv. AC Grazeland (Grazeland) in monoculture and binary mixtures at different maturity stages. Two cultivars of alfalfa (HiGest, and AC Grazeland) and their binary mixtures with hybrid bromegrass (HBG; cv. AC Success), grown in 2019 at two locations (Saskatoon and Lanigan), were cut at three maturity stages of alfalfa (1 = 10% bloom; 2 = 40% bloom; and 3 = 100% bloom). Rumen degradation characteristics, including rapidly degradable fraction (S), potentially degradable fraction (D), undegradable fraction (U), degradation rate (K(d)), lag time (T(0)), and effective degradability (ED) of each component were determined using in situ technique and were analyzed by a first-order kinetic equation described by Ørskov and McDonald with lag time. Generally, in alfalfa monoculture, S or D were decreased and U was increased without affecting K(d) and T(0), resulting in decreased ED fraction with increasing stage of maturity. In binary mixtures, plant maturity stages have negligible effects on rumen degradation characteristics of CP. HiGest had higher effective degradability of DM (EDDM) as well as of NDF (EDNDF) than Grazeland. In conclusion, HiGest had greater DM and NDF rumen degradation potential relative to Grazeland. HiGest and Grazeland were different in DM and CP degradation patterns, with HiGest having higher EDDM and EDCP than Grazeland.