Cows sick from winter crops
Southland farmers are being warned to be careful about transitioning cows onto winter crops after reports of stock becoming ill again.
VetSouth Winton veterinarian and director Mark Bryan said winter had gotten off to a bad start, with callouts made to farms because of sick cows after improper transitions onto winter crops.
This follows several years of animals suffering acidosis from fodder beet and HT (herbicide tolerant) swedes. The worst year for the region was 2014 when about 300 ewes and at least 200 dairy cows died after feeding on crops, with hundreds more becoming ill.
Transitioning cows to crops involves providing a supplementary feed, such as baleage, and gradually introducing crops.
Cows diets should not be changed abruptly because their rumen needs time to adjust to new feed. If the transition period is too short or cows consume too much crop too quickly, ruminal acidosis can occur.
Acidosis can cause lowered intakes, rumen stasis, and long lasting damage to rumens and livers and even death if cows are not removed from crop and treated.
‘‘It’s just an indication of how difficult it can be to transition onto fodder beet.’’
Bryan said farmers needed to monitor their stock closely to look out for signs of illness and take them off crops if signs of illness started to appear. ‘‘Ensure they have plenty of fibre.’’
Warning signs include weight loss and ill-thrift, down cows and photosensitivity.
Bryan said he had hoped there would be less issues this year, and had found many of the farms with illness had changed their transition systems this season. It was important to maintain a consistent transition system to avoid sickness, he said. ‘‘I think the issue is that when these cows go down it’s really hard to treat them and get them back up.’’
It wouldn’t just be one cow getting sick in a herd, instead there could be 30, 40 animals sick, he said.
Since it was expensive and hard to treat animals, many of the worst affected would have to be put down, he said.
Farmers are being told to remember that the first two weeks of winter were critical for cows and they needed to be managed well to keep them healthy throughout winter and into calving.
Bryan had hoped frosts throughout the region at the start of the season would have helped to prevent acidosis because it should have kept glucosinolate levels down. However, that had not been the case. Herbicide tolerant swedes have higher concentrations of glucosinolates, a naturally occurring compound in leaves which is toxic.