Swapping milk for electrolytes: investigating dairy calf activity and hunger after replacing a meal

Meredith Longer¹Megan Woodrum Setser^2,3Gracie Figueroa⁴David L Renaud¹Joao HC Costa³Katherine Creutzinger^3*

• ¹University of Guelph Department of Population Medicine, Guelph, Canada
• ²Department of Animal Science, University of Connecticut, Storrs, United States
• ³University of Vermont Department of Animal and Veterinary Science, Burlington, VT, United States
• ⁴University of Wisconsin-River Falls, River Falls, United States

Replacing a milk meal with electrolytes is often done to hydrate pre-weaned calves following transport or diarrhea, though the impact on calves’ hunger and activity is unknown. Therefore, the objective of this study was to investigate the effect of replacing a milk feeding with electrolytes on dairy calves’ motivation to drink milk at a subsequent meal, calf starter intake, and their activity. Dairy calves (n = 100; 23 ± 1 d of age) were enrolled in a crossover study that exposed calves to 2 milk (2.74 L) and 2 electrolyte (2.74 L of 252 mOSM/L solution) feedings in random order as their morning meal, with a washout period in between over two weeks. To measure calf motivation to drink milk, calves received either unaltered milk replacer or milk replacer with a bitter additive (0.35 g/L quinine hydrochloride dihydrate) as their evening meal. Calves were exposed to four daily combinations for treatment application (morning meal: electrolyte vs. milk) and test application (evening meal: bitter vs. regular milk): electrolytes and bitter milk, electrolytes and regular milk, milk and bitter milk, and milk and regular milk. Milk replacer, electrolyte, and calf starter intake were recorded for each calf. A subset of calves (n = 69) was outfitted with accelerometers to measure steps, activity index, lying time, and lying bouts which were summarized hourly for the eight hours between feedings on test days. Regardless of morning treatment, calves consumed less bitter milk than regular milk in the evening feeding, but an increase in calf willingness to consume bitter milk after replacing a meal with electrolytes was not observed. However, electrolyte-fed calves consumed more grain after the morning meal, took fewer steps, had a lower activity index, and spent less time lying at seven and eight hours following the morning feeding compared to milk-fed calves. Greater calf starter intake and less lying time during the hours before the evening feeding by the calves fed electrolytes in the morning compared to those fed milk suggests that substituting a milk meal with electrolytes meal may increase behaviors indicating hunger in pre-weaned calves.