As clover content in swards increases, bloat risk can increase. Damp, dull mornings like those earlier this week are the highest-risk periods for bloat, especially in fields with high clover content and lush grass. It’s a risk that needs to be managed; when it goes wrong it can go very wrong, with little warning. The problem is caused by cows gorging themselves on very lush grass and clover. This creates a froth in the rumen which prevents gas from escaping and the cow swells up and suffocates if untreated. It can happen quickly so a dead cow is often the first sign of a problem.
Treatment includes stabbing the cow to release the gas using a trocar and cannula, inserting a stomach tube down the neck to release the gas or drenching the cow with bloat oil or paraffin oil to disperse the froth. Prevention is tricky. Bloat oil can be added to the water but this option can be costly and it’s hard to source. Putting cows on 12-hour breaks in high-risk paddocks will allow them to eat more stem and fibre, which reduces the risks. Being vigilant is key, especially from now on. It’s a big downside to clover but seems to be much less of a problem on farms with lots of clover.
Spring-born calves should be around 28% of mature liveweight now. This means a herd with a mature liveweight of 550kg should be around 154kg and calves from a herd with a mature liveweight of 580kg should weigh around 162kg. It’s the genetic weight of the calf that should be estimated, not necessarily the existing herd, because breeding policy is changing and on the average farm younger animals will be bigger than existing cows when they get older.
Most calves are probably above target weight, which isn’t ideal as too heavy is as bad as too light. Meal should be cut off to calves that are on or above target because they don’t need it. Decent-quality grass should deliver 0.7kg to 0.8kg/day of liveweight gain. Later-born calves and lighter calves who need a higher daily liveweight gain will probably need some meal to keep performance up. Summer scour syndrome can often be a problem where calves are eating very lush grass which you would expect would deliver the highest liveweight gain. Grazing covers of 1,300kg/ha to 1,500kg/ha in a leader-follower-type system might work better than grazing calves in covers of 1,000kg/ha.
Some farmers are finding that calves are coughing, even after being dosed. Is this lungworm or a virus and is it affecting performance? It’s something you would need to get investigated. Dung samples are not very effective for detecting lungworm. A lung wash, which can be carried out by the vet, is much more accurate.
The Irish Grassland Association summer dairy tour is an online event this year focusing on clover. Two farms are being visited for a live discussion at 11am on 21 July. Kevin Moran from Caherlistrane in Co Galway and John Joe and Andrew O’Sullivan from Rosscarbery in Co Cork will outline their approach to establishing and managing clover and reducing chemical fertiliser use. No registration is required, just watch on the IGA website.