Collaborating Producer: Odell & Lillian Raymond, Peace River Alberta
Research Coordinator: Dr. Akim Omokanye
Many livestock producers try to extend the grazing season to reduce feed costs. Grazing annual forages is another such way to not only graze livestock longer into the fall or early winter, but also provide potentially higher quality forages. Brassicas, such as turnips, are one example of an annual forage that can be grazed effectively by cows. Turnips are high quality, high yielding, fast growing crops that are particularly suitable for grazing by livestock in the fall. Both tops (stems plus leaves) and roots (tubers) can be grazed and are very nutritious. Turnips produce forage of exceptionally high (often 85-95%) digestibility and the roots are rich in carbohydrates. Turnips tolerate temperatures down to -8 degrees C. Turnips require several days of temperatures continually below freezing to be killed. The objective of this study was to examine the production of turnips grown with or without oats.
The trial took place at Odell and Lillian Raymond’s farm, north of Peace River. A total of 90 acres was used for the trial. Land preparation consisted of deep tillage on oat stubble in the fall and cultivation in the spring. There were 3 treatments consisting of turnips alone (30 acres), turnips-oats intercrop (25 acres) and oats alone (35 acres). The variety of turnips used was Purple top and this was seeded at 2.5 lb/acre using a field cultivator with a Valmar on May 23, 2011 (for turnips alone field) and May 20 (for turnips-oats intercrop and oats alone fields). Purple top is a common turnip variety used for grazing. The oat variety used was Derby and this was seeded at 2.5 bushels/acre for the turnips-oats intercrop and oats alone fields. A hoe drill with a 7-inch spacing was used for seeding oats after turnips. Each treatment received 50 lb/acre N. No herbicide was applied to any of the treatments. All the crops were sampled for dry matter yield determination on September 1, 2011.
Dry Matter Yield and Feed Value
Forage DM yield was highest for the oats alone field (9678 lb/acre) and lowest for the turnips alone field (5569 lb/acre) (Table 1). For the turnips, the roots (tubers) formed the bulk of the total DM yield. The CP content of the crops was in the order of: turnips > turnips – oats intercrop > oats (Table 1). The high CP content obtained from the turnips (whole plant) resulted from the leaf component of the plant, which on its own had 23% CP compared to 12.17% CP from the tuber. Generally, oats alone forage consistently had lowTurnips alone Oats alone Turnips – oats intercrop Peace Country Beef & Forage Association 2011 Annual Report Page 34 er mineral (Ca & P) and higher detergent fibre (ADF & NDF) contents than the turnips – oats intercrop or turnips alone.
The oats alone forage had insufficient amounts of Ca and P to meet the suggested beef cattle requirements for both minerals. Though, turnip – oat intercrop had lower DM yield than the oats alone, in terms of quality, the turnip – oat intercrop was of higher nutritional quality. Cows eating the turnip – oat intercrop would have adequate amounts of CP, Ca and P needed for any stage of production.
Generally, turnips had excellent nutritional value with a high energy content (leaves have 68% total digestible nutrients; roots have 71% total digestible nutrients), and good protein levels (leaves have 23% crude protein; roots have 12% crude protein). In addition, the turnip – oat intercropped forage would have the tendency to be preferred and consumed more than the oats alone because of the lower NDF value. Their digestibility is also likely to be higher than those of the oats alone material, going by the ADF values. Earlier studies elsewhere have shown that turnips retain their nutrients late into the fall and are good in providing high quality and quantity forage for grazing livestock in the fall. Livestock eat the leaves and roots of turnip plants. Cattle will also dig the turnips up out of the ground. However, it is important to note the growth performance of turnips was not impressive in the turnips–oat intercrop. The turnip leaves and roots were small and in most cases, their roots were substantially smaller than those of the turnips alone field.
Cattle (108 cows, 98 calves, 7 yearlings & 4 bulls) were given 3/4 of an acre per day in the turnip—oat intercrop field, which resulted in approximately 21 days of extended grazing time. When placed in the turnips only field, animals were given 1 acre per day, which should have resulted in approximately 30 days of extra grazing. However, due to excessive moisture, turnip yield was lower, therefore fewer grazing days were actually available. At this feeding and stocking rate, animals were consuming approximately 2.5% of their bodyweight.