Evaluation of nutrient content of different harvest stages in switchgrass (<i>Panicum virgatum</i> L.) cultivars

<i>Panicum virgatum</i> L., also known as switchgrass, is a warm season short-day, C4-perennial crop gaining attention in feedstock production. The harvest stage of the forage crops and the cultivars used directly affect the feed quality as animal feed. In this study, differences were evaluated in various macro element contents of switchgrass (<i>Panicum virgatum</i> L.) cultivars at different harvest stages. Eight different switchgrass cultivars (Alamo, BoMaster, Kanlow, Cave in Rock, Long Island, Shawnee, Shelter, and Trailblazer) were evaluated in the study. According to the results of the study, significant differences were found among the cultivars studied for phosphate (P), potassium (K), calcium (Ca), and magnesium (Mg). The Long Island cultivar had the highest mineral concentration (0.223% P, 1.049% K, 0.581% Ca, and 0.201% Mg). As harvest proceeded, the levels of P and K in the plants decreased while the levels of Ca and Mg increased. The highest P (0.223%) and K (1.030%) values were obtained from plants harvested at the pre-flowering stage, while the highest Ca (0.538%) and Mg (0.183%) values were obtained from plants harvested at the full flowering stage. Switchgrass cultivars were found to be insufficient to meet animal needs for P and Ca content throughout the plant's harvest stages. Mg was found to be sufficient in all harvest stages, while K was sufficient in the first two harvest stages, pre-flowering and 50% flowering, but insufficient in the full flowering stage. The dry matter's Ca/P ratio, regardless of cultivar or harvest stage, posed no risk to animal health. The K/(Ca+Mg) ratio varied between 0.807 and 1.235 depending on the cultivar and harvest stage. This ratio does not pose any risk to animal health. Based on these results, it would be appropriate to supplement feed rations with materials containing P and Ca or to use switchgrass in animal feeding together with feeds rich in these minerals when using dry matter obtained from switchgrass cultivars alone as roughage. In general, although <i>Panicum virgatum</i> has an important potential as a feed source in animal nutrition, it needs to be supplemented with nutrient-containing additives. It would also be appropriate to determine the nutrient content of these varieties under different ecological conditions.