It is not uncommon for producers to graze annual crop stubble fields. This year, with feed supplies being in short supply, crop regrowth in silage or harvested fields is an option to extend the grazing season. There are risks associated with each of the crops being grazed.
Annual crop stubble fields have variable quality. Crop type, amount of grain thrown out by the combine, and weeds present influence nutrient availability. Often, low protein and high fibre found in the straw can restrict feed intake, causing cows to lose condition. A high calcium mineral is recommended.
Canola regrowth is a high protein and high energy forage. Quality can be as high as a good quality first cut alfalfa grass hay. Cattle may take a day or two to learn to graze the material. Concerns are with high nitrate and sulfur content. Nitrate above 1% on a dry basis can cause animal losses. The more concerning issue is with sulfur levels exceeding 0.5%, which causes polio. There are reports of animals dying from regrowth containing 0.8% sulfur or higher. Limiting access to the regrowth with electric fences and supplying an alternate feed is one option to safely graze the material.
Flax is a crop that is harvested late and generally does not regrow in the fall. But, in severe feed shortage areas, some fields can be grazed. High fibre levels make the straw hard for animals to digest, resulting in limited feed intake. Green flax straw remaining in the field can contain prussic acid. The active toxin is hydrogen cyanide. A poison that is very fast acting with the first symptoms being dead animals.
Cover crops are grazed late into the fall. A high protein and energy crop. Not a regrowth situation, but if there are brassica species present such as radish, turnip, forage rapeseed, and kale, these plants are sulfur accumulators. There are feed test results that have come back with levels similar to that found in canola regrowth.
Cutting the regrowth prior to grazing and sending a sample for analysis is recommended. The material is usually high quality and a forage that can be used. It might require more management, but the opportunity to reducing stored feed requirements and lowering winter feed costs are benefits that cannot be overlooked.
For additional information on grazing crop regrowth, contact Barry at 403-741-6032 or email@example.com