Presentation on theme: "Forage Macro-Minerals (Ca, P, K, Mg, Na, Cl, S) and Dairy Cow Requirements Jim Linn, PhD Professor Emeritus – University of Minnesota Milk Specialties."— Presentation transcript:
Forage Macro-Minerals (Ca, P, K, Mg, Na, Cl, S) and Dairy Cow Requirements Jim Linn, PhD Professor Emeritus – University of Minnesota Milk Specialties Global Waconia Farm Supply
Importance of Minerals Animal Health Production/Reproduction Ration cost Lactating Cow 8 to 10% of total $/cow/day 0.75 - 1.00 Close-Up Dry Cow 18 – 22% of total $/cow/day 0.75 - 1.00
Forage Mineral Analysis NIRS or Wet Chemistry? – NIRS doesn’t measure minerals only C,N,O bonds – Are the minerals reported on NIRS forage tests accurate? – At the end of the day, when nutritionists have several rations to formulate, can NIRS predicted forage minerals be used?
NIR Prediction of Minerals Haylage Calibration Data MineralMeanSECRSQSECV Ca188.8.131.52.16 P.34.04.61.04 Mg.32.05.69.05 K184.108.40.206.32 S.26.04.75.04 Source – Dairyland Labs, Arcadia WI SEC – Std Error Calibration – lower better (±1 SEC – 67% of values) RSQ – R 2 1 = perfect prediction SECV – Prediction validation – lower the better NIR mineral validity depends on good reference wet chemistry methods and equation(s) development
NIRS Analysis – Forage Minerals Macro Minerals – – Lactation rations Acceptable estimator – Ca, P, K, Mg and S Rationale – Most rations over formulated and supplemented – Small range in P, Mg and S within species – Salt meets Na and Cl req’t – Dry cow NIRS not recommended for mineral analysis Forages are large proportion of diet Accuracy needed for DCAD and requirements Trace minerals – NIRS not recommended
Magnesium Contribution From Feeds Lactating cow diet – 0.35% Mg lb Feed DM % Mg contribution lb or %
Potassium Mineral required in the highest amounts in lactating dairy cows K balance studies indicate 1.6% K needed in early lactation for positive balance Heat stress increases requirement Forage K >85% available
Potassium Contribution From Feeds Lactating cow diet – 1.5% K % K contribution lb or %
Close-up Dry Cow Diet % Macro Mineral from Forage 77% Forage diet – 13.7 lb Corn sil + 8.3 lb Grass Hay DM %
Minerals from Forages in Dry Cow Diets Forages can supply 20 to 70% a mineral Accuracy on mineral concentration in forages more important – less error tolerance Cation – Anion balance Metabolic problems – greater risk with mineral imbalance Wet chemistry analysis recommended for minerals in dry cow forages
Macro Minerals in Forage Summary Forages are an important source of most macro minerals in lactating and dry cow rations. Ration formulation needs to consider – Requirements – Sources – Amounts fed – excess as well as deficiencies – Interactions amongst minerals fed in excess
Macro Minerals in Forage Summary NIRS acceptable estimator of Ca, P, K, Mg and S in lactating rations. – Formulations usually exceed minimum requirements Forages are a greater proportion of dry cow ration and mineral formulation requires accuracy – Wet Chemistry mineral analysis recommended. Precision feeding lactation and/or dry cow diets require wet chemistry analysis of minerals.