Early Lactation Production, Body Condition, and Incidence of Disease in Holstein Cows Fed a Low-Potassium Diet Alone or Supplemented with Chloride Prepartum

The objective of the trial was to determine if supplementing a low-K prepartum diet (< 1.20% DM) with additional chloride for 3 wk before calving would affect milk yield, body condition, or incidence of disease during the first 90 DIM. Two hundred multiparous Holstein cows and 132 Holstein heifers approaching their first lactation (primiparous cows) were assigned to either a control treatment consisting of a low-K prepartum diet with a forage base of straw and corn silage, or a low-K prepartum diet with a forage base of straw and corn silage supplemented with chloride (0.54 to 0.78% DM). Cows were fed differing rations and housed in separate pens for the prepartum period (−21 to 0 DIM) but were comingled after calving. Mean urine pH during the prefresh period was 6.6 and 8.0 for multiparous chloride-supplemented and multiparous control cows, respectively. Plasma Ca levels at calving in multiparous cows were higher for cows fed supplemental chloride than for those fed the low-K control diet with means of 7.9 vs. 8.6 mg/dL for control vs. chloride-supplemented cows. Chloride supplementation had no effect on disease incidence or body condition loss. Chloride supplementation positively affected yield of milk, milk protein, and milk solids of cows with 3 or more lactations but did not affect production in first or second parity. Supplemental chloride added to a low-K prepartum diet improved Ca status and increased productivity of cows with 3 or more lactations.