Flexible grazing options for forage rape

FutureDairy’s researchers have discovered that forage rape is more resilient to different grazing approaches than previously believed. This offers new flexibility in grazing options for dairy farmers who must restrict the amount of forage rape consumed by their cows to prevent nitrate toxicity. Forage rape – also known as brassica – is grown by dairy farmers to boost feed supply in autumn, when there is often a shortage of pasture availability. Associate Professor Yani Garcia, FutureDairy Project Leader, says some dairy farmers have been put off growing forage rape because of the logistical challenge of restricting its intake, especially with large herds. Intake by dairy cows must be restricted to 5kg DM/cow/day avoid nitrate toxicity. The current practice is to stagger sowing dates of areas of forage rape to provide a continuous supply of the amount of forage rape needed. The research, conducted by Damien Tanner and Edward Stefanski, investigated two different grazing approaches – multiple and take-all. Multiple grazing involves lightly grazing the crop two or more times, to allow regrowth to occur when it reaches a yield of about 5t DM/ha. Take all grazing involves grazing the crop heavily a single time, when it reaches a maximum yield (5-7t DM/ha). “We were a bit surprised to find that forage rape is resilient to both multiple and heavy grazing,” said Dr Garcia. Good re-growth occurred from both grazing approaches which means a less controlled form of multiple grazing is possible. “The good news for dairy farmers is that they can use a combination of grazing approaches for forage rape. This gives them the flexibility to choose a grazing approach that bests suits their situation at a given time,” said Dr Garcia. Flexible grazing is a less risky alternative to staggered sowing dates which can be delayed due to rain. The study also compared three sowing rates (2, 3.5 and 5 kg/ha). Results showed the lower sowing rate can be used without any adverse impact on crop yield. Dr Garcia reminded farmers that the keys to success with forage rape are sowing early, good weed control and providing adequate fertiliser.