The widespread and heavy rain over the last week has been of great benefit in terms of grass growth. With the exception of the most extremely affected farms, all fields have greened up and are now actively growing again.
It gives confidence that some of the lost ground will be made up again before the end of the grazing season.
However, big challenges remain and farmers will have to continue to feed heavy for weeks longer. Rotation length should be as slow as possible to give covers a chance to recover.
Supplement fed now gives the highest return, so don’t be afraid to go on a 35- to 40-day round.
A good few farmers are asking about fertiliser. While the agronomic response at this time of year is generally much lower than in spring, given where most farms are at in terms of grass supply there will be a strong economic response to fertiliser this autumn.
If nitrogen is costing €2/kg and if every kilo grows say 20kg DM/ha, the cost of the grass is 10c/kg DM compared to meal at 46c/kg DM or silage at 25c/kg DM.
How much N to spread is debatable but I’d be inclined to go in at 20-25kg N/ha (16-20 units/acre). The unknown is how much background nitrogen will be released. The start of the closed period for chemical fertiliser is Thursday 15 September.
Risk of death
Watch out for signs of bloat and nitrate poisoning over the coming weeks. Lush grass with a high nitrogen and/or potash uptake seem to be high-risk swards for both.
Bloat is the more common of the two, but nitrates poisoning can be a particular risk after a long dry spell. Fields that were reseeded this year will have a high nitrate level in the grass.
The problem with both bloat and nitrate poisoning is that the first signs are usually a dead cow or cows.
Be particularly careful if blanket spreading fertiliser ahead of the herd as nitrate levels in the grass are probably highest four to five days after spreading CAN and a week or so after spreading urea.
Nitrate poisoning can occur in fields that don’t get any chemical nitrogen, so it is not the only risk factor.
Monitor cows one to two hours after letting them into a very lush, high-risk paddock. If concerned, alternate grazings between lush and stemmy paddocks, with lush paddocks grazed in the evening where the risk is lower.
Treatment for nitrate poisoning is giving methylene blue into the vein, but death usually occurs quickly, so call the vet as soon as a case is suspected.
Salmonella vaccine should be given to pregnant cows now. The vaccine prevents early abortions caused by salmonella pathogens.
In-calf heifers and cows being vaccinated for the first time will need to be done twice, three weeks apart, while cows that were vaccinated previously just need the booster shot.
Depending on what protocol the farm is on, herds that vaccinate annually in January for IBR may need to consider doing the calves in the next few weeks with an IBR live vaccine followed by inactive vaccine in January at the same time as the rest of the herd. Consult your vet on the best protocols.