0610 Nutritive quality and forage yield of three Brassica varieties for use in livestock grazing systems

Resumo

Brassicas are gaining popularity as high-quality forage for pasture-based livestock producers due to their use to extend the fall grazing season and during the summer forage slump. Little research has been conducted to evaluate forage yield and nutritive value of brassica species. A study was designed to compare forage yield and nutrient composition of ‘Barsica’ rapeseed (Brassica napus), ‘Inspiration’ canola (B. napus), ‘Appin’ turnip (B. rapa), and ‘KB Supreme’ annual ryegrass (Lolium multiflorum). The study was conducted as a completely randomized block (n = 4) design at The Pennsylvania State University Russell Larson Agricultural Research Farm in Rock Springs, PA. Plots were drilled (Wintersteiger Plotseed XL, Salt Lake City, UT) into a prepared seed bed in August 2015 and fertilized with 71 kg N/ha. Potash, P, and lime were added according to soil tests. Forages were sampled biweekly during October and November using a 0.1-m2 quadrat and clipped to 4 cm. Samples were dried at 60°C using a forced-air oven for 48 h, ground to 1 mm using a Willey Mill (Thomas Scientific Inc., Philadelphia, PA), and submitted to Dairy One Laboratories (Ithaca, NY) for wet chemistry analysis. Statistical analysis was conducted using Proc GLIMMIX (SAS Inc., Carey, NC) with α = 0.05. Forage yield was not different among brassicas (1023 ± 108.5 kg DM/ha), which were greater (P ≤ 0.0001) than ryegrass (242 ± 108.5 kg DM/ha). Although CP was greater (P < 0.032) in ryegrass than the brassicas (33.1 vs. 29.2 ± 1.44%), degradable and soluble protein fractions were lower (P < 0.032) in ryegrass than all brassicas (76 vs. 84 ± 0.71% and 49 vs. 53 ± 1.12%, respectively). Brassicas contained similar NDF and ADF concentrations (18.7 ± 0.94 and 14.4 ± 0.77%, respectively) but were lower (P < 0.0001) than ryegrass (35.4 ± 0.94 and 17.5 ± 0.77%, respectively). Both canola and rapeseed had greater (P < 0.001) NEM and NEL (1.65 ± 0.02 and 1.72 ± 0.01 Mcal/kg, respectively) than turnip or ryegrass (1.45 ± 0.02 and 1.54 ± 0.01 Mcal/kg, respectively). Inclusion of brassicas in a cool-season pasture rotation has the potential to increase animal productivity and reduce the need for stored feed during periods of perennial cool-season forage shortages, including mid-summer and late fall.