Racing NSW stewards have issued a warning to horse trainers about "some commercially available feeds that have been found to contain levels of cobalt above that specified on the labels".
Analysis of feed samples "from Barastoc Phar Lap Oats-Free Muesli Concentrated Feed manufactured on 23 March 2017 and 22 May 2017" was found to contain levels of cobalt "excessively above the disclosed analysis on the product label".
Earlier this month, Randwick trainer Ron Quinton and country-based conditioner Gordon Yorke were advised they will face separate stewards' inquiries after horses they train returned cobalt readings above the threshold.
"Stewards have ordered the analysis of feed and supplements taken from Mr Quinton's stable," the stewards' report read.
The legal level of cobalt in a horse's system cannot be above the legal threshold of "a mass concentration of 100 micrograms per litre in urine or 25 micrograms per litre in plasma".
Meanwhile, Stewards have also issued a general notice to trainers regarding feed and supplements.
"Racing NSW Stewards are aware that some trainers are having manufacturers prepare custom-made horse feeds, feed additives, and/or supplements. It is understood that some manufacturers are not listing - a. all active constituents; and/or b. the concentration of all active constituents, on the labels of their custom-made products," the release said.
"Trainers are reminded of their obligations to know what they are feeding, and/or administering to, their horses, including the concentrations of active constituents of any products used by them."