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

**Background:** Alfalfa is widely used as forage for livestock due to its high nutrient content, but its digestibility is limited by lignin content. Lignin is a complex structural polymer that increases as plants mature, reducing the accessibility of cellulose and hemicellulose to rumen microbial enzymes. Alforex Seeds released a low-lignin alfalfa cultivar called Hi-Gest® 360 through conventional plant breeding. This study aimed to evaluate the rumen degradation kinetics of this new cultivar compared to conventional alfalfa AC Grazeland under Saskatchewan growing conditions.

**Methods:** Forage samples were collected from field trials established in 2017 at two Saskatchewan sites: Saskatoon (Orthic Dark Brown Chernozem soil) and Lanigan (Chernozemic Black Oxbow soils). Forty-eight plots per site (1.2 × 6 m each) were randomly assigned to 4 replicated treatments: two alfalfa cultivars (Hi-Gest® 360 and AC Grazeland) in monoculture or binary mixtures with AC Success hybrid bromegrass, harvested at three maturity stages (10%, 40%, and 100% bloom). Eight Black Angus cows (876 ± 34 kg) fitted with rumen cannulae were used for in situ incubation. Samples were incubated for 0, 4, 8, 12, 24, 48, and 72 hours. Rumen degradation characteristics were determined using the first-order kinetic model of Ørskov and McDonald with lag time. Statistical analysis used the GLIMMIX procedure in SAS 9.4 with significance set at p ≤ 0.05.

**Key Results:** Hi-Gest® 360 had 8.6% less acid detergent lignin compared to AC Grazeland (59.5 vs. 65.1 g kg⁻¹ DM). At the Saskatoon site, HiGest had 11.8% lower undegradable DM fraction (246 vs. 279 g kg⁻¹ DM; p < 0.001) and greater EDDM (621 vs. 603 g kg⁻¹ DM; p = 0.047). At Lanigan, HiGest had 14.7% lower undegradable DM fraction (320 vs. 375 g kg⁻¹ DM; p < 0.001) and 7.2% greater EDDM (520 vs. 485 g kg⁻¹ DM; p = 0.002). For NDF, HiGest showed 17.5% lower undegradable NDF fraction at Saskatoon (450 vs. 529 g kg⁻¹ DM; p < 0.001) and 10% lower at Lanigan (470 vs. 517 g kg⁻¹ DM; p = 0.019). EDNDF was 19.3% greater for HiGest at Saskatoon (340 vs. 285 g kg⁻¹ NDF; p = 0.005) and 6.5% greater at Lanigan (265 vs. 249 g kg⁻¹ NDF; p < 0.043). For CP degradation at Lanigan, HiGest had 28% lower undegradable CP fraction (237 vs. 329 g kg⁻¹ CP; p = 0.001) and 13.6% greater EDCP (608 vs. 535 g kg⁻¹ CP; p < 0.001). As maturity advanced, degradability declined across all forages. Importantly, HiGest at stage 3 was comparable to Grazeland at stage 2 for EDDM and EDNDF, indicating maintained quality with delayed harvest. Each percentage unit increase in lignin concentration decreased EDNDF by 1.2 percentage units.

**Clinical Implications:** The low-lignin Hi-Gest® 360 alfalfa demonstrates superior rumen degradability of dry matter, crude protein, and neutral detergent fiber compared to conventional AC Grazeland alfalfa. The finding that HiGest maintains quality for up to two weeks beyond the optimal harvest stage provides producers with greater management flexibility. This wider harvest window could be particularly valuable in regions with unpredictable weather patterns, allowing farmers to delay cutting without sacrificing forage quality. The improved fiber degradability may translate to better animal performance through increased feed efficiency. However, the authors note these results are based on a single year of data and require confirmation across multiple growing seasons and conditions.