PSIV-A-5 - Variation in nutritive value for beef cattle grazing cover crop mix plots with five different forage species

Abstract: The objective was to evaluate the variation in mixed cover crop plots on yield and in situ dry matter (DM) disappearance to determine nutritive grazing value for beef cattle. Beyond improving soil conditions, cover crops can provide additional benefits as a source of nutrition for grazing cattle. The cover crop mix included 10% annual ryegrass, 39% oats, 45% cereal rye, 3% forage turnips, and 3% dwarf essex rape. This experiment was conducted on three 0.40-hectare plots at Western Illinois University Kerr Farm, Macomb, IL to assess variation in forage DM yield, forage height before and after grazing, and in situ DM disappearance. The cover crops were planted September 1, 2023 at a rate of 84.5 kg per ha with a no-till drill following crop harvest. In mid-April of 2024, each plot was strip grazed for 24 hours by 53 cow-calf pairs and seven open cows. Plots were randomly sampled in four locations before and after grazing within a 0.40 m2 forage ring to determine forage yield, height, and nutritive value. All forage was clipped at approximately 12 cm to mimic grazing. Samples were analyzed at Rock River Laboratories (Watertown, WI) for crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and total digestible nutrients (TDN). In situ DM disappearance was determined using ruminally cannulated lactating beef cows (n = 2). Data were analyzed using the MIXED procedure of SAS 9.4. Nutritional value among the three plots ranged from 11-15% for CP, 41-46% for NDF, 31-39% for ADF, and 56-63% for TDN. Plot two yielded (P < 0.01) the most DM at 3,391 kg per ha compared with plot one and three which yielded 1,800 and 1,849 kg per ha, respectively. While post-graze DM did not differ among plots; remaining DM ranged from 1466 to 325 kg per ha. Forage height did not differ before or after grazing among plots. There was a plot by hour interaction (P < 0.01) for in situ DM disappearance. At 24 h in situ incubation, plot one and three had greater DM disappearance compared with plot two. However, plot two had greater DM disappearance than plot one and three after 48 h in situ incubation. Overall, the nutritive value and in situ DM disappearance did vary among three plots containing a mix of five cover crop forages. Despite variation, cover crops can provide an excellent source of nutrition for cattle grazing plots prior to the typical grazing season.