Preference and drinking behavior of lactating dairy cows offered water with different concentrations, valences, and sources of iron

Drinking water can contain high concentrations of Fe, mainly of the ferrous (Fe2+) valence. The current recommended upper tolerable concentration of Fe in drinking water for cattle (0.3 mg/L) comes from guidelines for human palatability, but cattle may be able to tolerate higher concentrations. Our objective was to determine the effects of varying concentrations of ferrous (Fe2+) or ferric (Fe3+) iron and Fe salt source on lactating dairy cows' preferences for and drinking behavior of water offered as choices ad libitum. In 4 separate experiments, cows were offered pairs of water treatments for 22-h periods and water intake and drinking behavior were recorded. In experiment 1, treatments were 0, 4, or 8 mg of total recoverable Fe/L from ferrous lactate. Cows exhibited no preference between water with 0 or 4 mg of Fe/L, but water intake was less with 8 compared with 0 or 4 mg of Fe/L. Also, cows spent less time drinking water containing 8 mg of Fe/L. Total time spent drinking correlated positively with water intake when pooled across treatments. In experiment 2, treatments were 0 or 8 mg of Fe/L from either ferrous sulfate (FeSO4) or ferric sulfate [Fe2(SO4)3]. Water intake did not differ among treatments. In experiment 3, treatments were 0 (control), 12.5, or 8 mg of Fe/L from ferrous chloride (FeCl2) or ferric chloride (FeCl3), respectively. Again, cows exhibited no preference among treatments. In experiment 4, treatments were 0 or 8 mg of Fe/L from ferrous lactate [Fe(C3H5O3)2], ferrous sulfate (FeSO4), or ferrous chloride (FeCl2). Cows preferred to drink water without added Fe, but did not exhibit any preference among waters containing the Fe sources with different anionic moieties. Cows spent less time drinking and drank less frequently when offered water containing 12.5 mg of total recoverable Fe/L from ferrous chloride compared with 8.0 mg of Fe/L from ferrous lactate or ferrous sulfate. Water intake correlated positively with both drinking duration and frequency when pooled across treatments in experiment 4. Overall, our results indicate that upon first exposure to drinking water, lactating dairy cows tolerate concentrations of Fe up to 4 mg/L from ferrous lactate without reducing water intake; however, water intake was reduced with 8 mg of total recoverable Fe. Preference did not appear to be influenced by Fe valence or added Fe source.