At the recent teagasc Moorepark milk-quality conference, researcher Bernadette O’Brien said iodine tends to be supplemented at farm level in the expectation of increasing cow health and fertility.
Teagasc carried out trials due to concerns such practices may result in high milk iodine, which could affect ingredients for the manufacture of infant formula and important Irish export product.
In the trials, 30 lactating cows were fed concentrates containing 10mg of iodine per kg for 35 days. During days 15 to 21, teat disinfection was applied in addition to the dietary iodine — either non-iodine (chlorhexidine) post-milking spray; 0.5% iodine post-milking spray; or 0.5% iodine pre and post-milking spray.
Cow milk yield was 21.3 kg/day. Individual cow milk samples were analysed for iodine concentration on two days at the end of each treatment period.
Dietary supplementation of iodine at both 30mg and 70mg per day increased milk iodine concentrations significantly, from 155 to 474 and 511 micrograms/kg, respectively (target values are 250 micrograms/kg).
Teat disinfection both before and after milking increased milk iodine concentration, at dietary supplementation levels of 0mg, 30mg, and 70mg/day, compared with a non-iodine teat disinfectant.
* There was also advice at the milk-quality conference that the dry period (when milk is not being used for human consumption) is the most suitable time for flukicide treatment.
Researcher Clare Power revealed that residues occur in cheese, butter, and skim milk powder at different rates, depending on the drug used.
Pasteurisation or heat treatment during spray drying didn’t reduce residues, which are attributed to animals being improperly treated, or improper observation of milk withdrawal periods.