DCAD Nutrition

Talking Points

• The Transition Cow
• Understanding DCAD
• Strategies to Reduce the Incidence of Hypocalcemia

The Transition Cow:

Importance of Transition Cow Nutrition

• Transition period: the time comprising 3-4 weeks before to 2-4 weeks after calving
• Proper management of dry cows should be thought of as an investment in the next lactation
• One of the major nutritional objectives should be to control clinical milk fever and subclinical hypocalcemia
• Mineral nutrition is key: as mineral concentrations in cells and tissues need to be maintained within narrow limits
• Deficiencies and excesses can lead to health/metabolic disorders and reduced performance
• Major economic impact

The Transition Cow:

Plasma Ca Concentration in Cows in Negative or Positive Calcium Balance Prior to Calving

The Transition Cow:

Incidence of Hypocalcemia in USA Confinement Herds

The Transition Cow:

Hypocalcemia Can Cause Health/Metabolic Disorders

• Lactation Severely Strains Calcium Balance Due to Calcium Secreted in Milk
• Calcium Ion is Necessary for Normal Muscle Function
• Two Primary Categories
  • Clinical “Milk Fever”
  • Subclinical Hypocalcemia

The Transition Cow:

A. Clinical "Milk Fever"

• Clinical Milk Fever
  • Unsteady Gait, Trembles, Difficulty Rising, Death
• Affects 5-7% of all adult dairy cows in US
  • Jordan and Fourdraine, 1993
• Milk Production decreases 14% in affected cows
• Eliminating milk fever, savings to the US dairy industry of $140M

The Transition Cow:

B. Subclinical Hypocalcemia

• Subclinical form of hypocalcemia: 66% of the dairy cows
  • Beede, et al.,1992
• Hypocalcemia is associated with numerous health disorders and reduced performance:
  • Mastitis, Ketosis, Dystocia, Retained Fetal Membranes, Prolased Uterus, Uterine Tone, Metritis, Udder Edema, Displaced Abomasa, Fatty Liver, Immune Function, Reduced Intake, Contractility of Ruminal Tissue, Reproductive Performance, Lactational Yield (Goff, et al., 1990-2004)
  • Estimated cost of health disorders:
    
    

    Metabolic Event	Estimated $/Incidence*
    Milk Fever	$344.00
    Retained Placenta	$285.00
    Ketosis	$145.00
    Displaced Abomasum	$340.00

    
    *cost per case, from lost or discarded milk, veterinary fees, labor, drugs, culling.
    
    C. Guard et al., 1996

The Transition Cow:

Lactational Incidence Risks, Milk Losses and Median Days Postpartum of Disorders in 8070 Multiparous Holstein Cows in New York State

Understanding DCAD:

Groundbreaking Studies on Etiology of Milk Fever

Craige and Stoll (1947) prevented relapses to milk fever by administration of blood acidifying agents.

Norway - Ender and Dishington (1971) discover that diets containing forages treated with inorganic strong acids prevent milk fever.

Canada - Block (1984) demonstrates that the Norwegian studies were correct and further defines the impact anionic salts have on milk production.

Understanding DCAD:

The Science of Dietary Cation-Anion Difference (DCAD)

• DCAD is expressed as the difference between cations and anions: (Na+K)-(Cl+S)
• Most dry cow rations have a DCAD of +50 to +300 mEq/kg
• Cations: positively charged electrolytes: Na, K, Ca, Mg
• Anions: negatively charged electrolytes: Cl, S, P
• Strongest ionic effect on acid-base balance is: K, Na, Cl, S
• Calculation in Milliequivalents (mEq)
  • Predicts whether a diet will evoke an acidic or alkaline response

Understanding DCAD:

The Science of DCAD - Cations

• Introduction of cations (K, Na) into the diet creates a mild metabolic alkalosis – alkaline diet
• Readily absorbable dietary cations (K, Na) alkalinize the blood and interfere with parathyroid hormone function resulting in hypocalcemia
  • Metabolic alkalosis reduces tissue responsiveness in both skeletal and renal tissue to PTH, resulting in reduced conversion of 1,25-(OH)D3 to the active form 1,25-dihydroxycholecalciferol or vitamin D3 disrupting calcium homeostasis (Goff & Horst 1997)

Understanding DCAD:

High K diets raise blood pH preventing Calcium regulation by parathyroid hormone

Understanding DCAD:

The Science of DCAD - Anions

• Introduction of anions (Cl, S) into the diet creates a mild metabolic acidosis – acidic diet
• Inflow of anions: triggers bone & kidney release of CO3 (buffer), bone Ca & P mobilization, Ca pooling on bone surface and increased blood Ca levels
• Metabolic acidosis stimulates PTH, vitamin D synthesis and bone Ca mobilization
  • Decreasing the DCAD during the last 3 weeks prior to parturition alters acid-base status improving Ca homeostasis by increasing PTH responsiveness and markedly reducing hypocalcemia (Moore 2000, Goff 2003, Joyce 1997).

Understanding DCAD:

Ca Homeostasis

Understanding DCAD:

Ca Homeostasis

Strategies to Reduce the Incidence of Hypocalcemia:

Overview

Strategies to Reduce the Incidence of Hypocalcemia:

Anionic Supplementation

• Anionic supplements (Acidic) can successfully increase ionized calcium and reduce hypocalcemia
  • Common sources of anions include Ammonium Chloride, HCl, Ammonium Sulfate, Magnesium Sulfate, Calcium Chloride, Calcium Sulfate and Magnesium Chloride
  • Decreases in dry matter intake on some anionic diets, especially for primiparous cows are well documented in the literature (Moore 2000, Vagnoni 1998, Joyce 1997, Horst 1994, Oetzel 1993)
  • New generation products complexing anions with more palatable carriers has largely reduced the intake problems, i.e. Animate
  • A DCAD of -15 meq/100 g is usually effective in preventing most cases of hypocalcemia (Moore 1997)
  • Urine pH helps to determine the right level of anions to add to the diet
    • Target Urine pH; 6.2 to 6.8
    • Do not go below a urine pH of 5.3 as you may cause metabolic acidosis

Strategies to Reduce the Incidence of Hypocalcemia:

Recommended Major Mineral Profile for Close-up Dry Cows using Anionic Supplementation

• (Ca) 1.2 to 1.5% : Higher Ca levels needed for increased intestinal absorption and reduction of Hypocalcemia
• (P) 0.4%: Maintain required blood P levels
• (Mg) 0.4% : Promotes Ca mobilization from bone, reduces the incidence of milk fever and tetany
• (S) 0.3-0.4% : Supports N:S ratio, microbial protein production, starch and cellulose digestion, anionic effect promotes Ca mobilization (strong anion)
• (Na)* 0.1% : Antagonistic, keep low as possible (strong cation)
• (K)* 0.7% : Antagonistic, keep low as possible (strong cation)
• (Cl) 0.8% : Anionic effect promotes Ca mobilization, Cl diets > 0.8% reduce palatability and dietary intake (strong anion)

* Na and K promote milk fever and other post-calving disorders in the fresh cow

Strategies to Reduce the Incidence of Hypocalcemia:

Recommended Major Mineral Profile for Close-up Dry Cows using Anionic Supplementation

274 Holstein cows fed conventional transition ration (50-90g Ca/d) w/o anionic salts (Oetzel).

• 51% were subclinically hypocalcemic at calving
• 10% had clinical milk fevers
• 39% were normal

284 Holstein cows fed transition diet containing anionic salts (Beede).

• 20% were subclinically hypocalcemic at calving
• 4% had clinical milk fevers
• 76% were normal