We plant acres of turnips and other brassicas but not to harvest for the market. Our lambs love turnips and turnips are a great food for growing lambs even in early winter.
Lambs do a great job of harvesting turnips without the use of petroleum powered equipment. They start with the greens. If managed so the growing tip is left on the bulb the greens will regrow for an additional harvest. Late in the season, after the first frost, the sugars increase in the bulb and the lambs dig them out of the ground for another harvest. One field of turnips usually provides 3 quality harvests for growing lambs.
Forage brassica crops include a wide variety of turnips, swede, rape and kale. Some of the brassicas are developed to provide heavy green growth with minimal bulbs. Others provide the standard purple topped bulb common at the grocery store. Turnip greens are high in protein (up to 20%) and provide a good growing ration for lambs while the bulb is lower in protein (8-12%) but is higher in carbohydrates and provides the additional energy lambs crave when the nights turn cold in the fall and early winter.
In the upper Midwest the growing season for native grasses is short. By August the sugars begin to drop into the roots of the grass so little nutrition is available for growing young animals. Annual forages, such as brassicas, are important to provide the protein and energy required by lambs especially during the fall and early winter while increasing their grazing options.