Management and Environment Effects on Brassica Forage Quality

Abstract

AbstractForage Brassica spp. have been shown to produce adequate amounts of herbage during the cooler months of the fall, thus allowing extension of the grazing season in higher latitudes. The objective of this study was to determine if the nutritive quality of initial and regrowth herbage was influenced by planting and harvest date. In 1987, 1988, and 1989, three Brassica spp. (rape [B. oleracea L.], turnip [B. rapa L.] and turnip hybrid [B. rapa L. × B. pekinensis L.]) were planted in late May to early June, late June to early July, and late July to early August and were harvested each year at 64, 76, or 85 DAP. The plants regrew 60, 70, or 80 d and were harvested. Nutritive components measured were CP, NDF, ADF, Ca, Mg, and P. Nutritive levels declined with warmer temperatures and low soil moisture levels particularly during July and August. Neutral‐detergent fiber and ADF levels were higher, while the CP levels were lower in herbage from the earliest planting date compared with the later planting dates, regardless of species and year. The levels of Ca, Mg, and P were influenced by species and planting date. In general, the regrowth herbage had a lower fiber and a higher protein content than the initial herbage. The variation in nutritive quality among the three species was relatively small. Of more importance to the producer is that the quality of brassica herbage is more comparable to a concentrate than a traditional forage because of the relatively low fiber and high protein content.