| Summary: | Until recently, occurrence of milk fever (MF) has been attributed to prepartum
calcium intake. However, researchers in Iowa have concluded that high prepartum dietary
potassium (K) is the major cause of MF. Potassium concentrations have been increasing
on manure fertilized soils over the last 20 years. Grasses grown on these fields mirror the
increase in available soil K. When high K forages are fed to dry cows, it has been
associated with increased MF in some, but not all cases. Our objective was to identify
factors that differed between low and high occurrence of disorders when high K forages
were fed.
For 1 yr, monthly interviews were conducted on 10 dairies in Western Oregon.
Close-up rations, dystocia rating, crowding, and cow comfort data were collected. Cows
were diagnosed healthy or having one or more of the following metabolic diseases: MF,
retained fetal membranes (RFM), and left displacement of the abomasum (LDA).
Feedstuffs were collected each month and analyzed for dry matter, crude protein (CP),
acid detergent fiber (ADF), and macrominerals.
Of the multiparous cows (n=3,587) included, incidences of MF, RFM and LDA
were 3.6, 11.3, and 1.5%, respectively. Increasing MF occurrence was associated with uncomfortable conditions, dystocia, increasing prepartum dietary Na and ADF, and increasing Ca to P ratios; there was also a dietary K by Mg concentration interaction. Increased dietary concentrations of Mg can prevent MF if dietary K is <2.6%. In addition, dietary conditions of K >2.6% and Mg >0.4% increase the occurrence of MF. Inversely, high concentrations of K can prevent MF in a Mg deficient diet.
Dietary factors associated with an increase in the occurrence of RFM are increased dietary concentrations of Ca, S, CP, use of anionic salts, and the K forage source. Factors associated with an increase in hypocalcemia in the postpartum cow are crowding, uncomfortable housing, and a dietary K by Mg concentration interaction. In conclusion, improved cow comfort, and the addition of Mg to high K forage diets could decrease the risk of the cow exhibiting MF, RFM, and hypocalcemia. === Graduation date: 1999
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