Effect of dietary iron, copper and zinc chelates of nitrilotriacetic acid (NTA) on trace metal concentrations in rat milk and maternal and pup tissues

The effects of maternal dietary trace mineral supplementation on the elemental composition of rat milk, dam and pup tissues have been investigated. Rats were fed a stock diet and were given water with no supplement or nitrilotriacetic acid (NTA) chelates of iron (FeNTA), copper (CuNTA), zinc (ZnNTA) or NTA alone (NTA) from day 7 to day 19 postpartum. Half of the dams in each diet group were serially milked on days 7, 13 and 19. The other half were terminally milked only (on day 19). At the last day of the experiment, liver, brain, spleen and kidney were taken from dams and pups. Iron was increased in some dam and pup tissues, as well as in milk, by FeNTA; copper and zinc contents were not altered. Feeding CuNTA caused increased concentration of copper in some dam and pup tissues, as well as in milk; zinc and iron were not affected. Unlike FeNTA and CuNTA, ZnNTA did not increase zinc concentration of the milk or the tissues. NTA alone had no significant effect on any parameter examined. Milk from dams which had been serially milked had higher zinc and iron concentrations than milk from terminally milked dams regardless of diet group. In all diet groups, pups from serially milked dams had higher liver, spleen and kidney iron concentrations than pups from terminally milked dams. These data show directly that iron and copper contents of milk can be raised by supplementation of iron and copper as NTA chelates and that this increase is reflected in the suckling pup, while zinc concentrations were not affected by this technique. Additionally, these data show that the frequency of experimental milking can change the trace mineral composition of the milk, and that this change is reflected in the suckling pup. This finding must be taken into consideration in the design of experiments in which milk is to be collected.