Productivity and Nutritive Quality of Three Brassica Varieties for Use in Pasture-Based Systems.

Brassicas are gaining popularity among pasture-based livestock producers to extend fall grazing and during the ‘summer slump.’ A 2-yr study was conducted to compare biomass production and nutrient composition of ‘Barisca’ rapeseed (RAP; Brassica napus L.), ‘Inspiration’ canola (CAN; B. napus L.), ‘Appin’ turnip (TUR; B. rapa L.), and ‘KB Supreme’ annual ryegrass (ARG; Lolium multiflorum Lam.). The study was conducted as a completely randomized block (n = 4) at the Pennsylvania State University Russell Larson Agricultural Research Farm in Rock Springs, PA. Plots were planted into a prepared seedbed in August 2015 and 2016 and fertilized at the time of planting with 71 kg N ha^-1. Potash, P, and lime were added according to soil test results. Forage was sampled biweekly during October and November using a 0.1-m² quadrat and were dried, ground, and submitted to DairyOne Laboratories (Ithaca, NY) for wet chemistry analysis of nutritional composition. There was a significant (P = 0.05) forage × year interaction for seasonal biomass production. In 2015, RAP, CAN, and TUR had greater (P < 0.01) seasonal biomass than ARG (1,600 and 471 kg ha^-1, respectively). Conversely in 2016, there was no significant (P > 0.14) effect of treatment on seasonal biomass accumulation (730 kg ha^-1). Annual ryegrass had the greatest (P < 0.01) CP concentration (293 g kg^-1) of all treatments and RAP was greater (P = 0.03) than TUR (270 and 253 g kg^-1, respectively). The NDF or ADF concentrations were similar (P > 0.06) among brassica treatments (161 and 136 g kg^-1, respectively) but were greater (P < 0.01) in ARG (346 and 173 g kg^-1, respectively). While brassicas showed superior biomass in 2015, the hotter and drier fall of 2016 had a significant impact on biomass production in 2016 without impacting nutritive value.