Little calf
29 Sep
Hypocalcemia

Relationship of serum calcium levels with health problems and milk production

Joaquin Ventura & Fernando Diaz

Calcium is a fundamental mineral for the proper functioning of the body. It has multiple functions, from structural in bones and teeth, to its participation in the transmission of nerve impulses, through its role in muscle contraction, blood clotting, the transport of various elements through cell membranes as well as many others.

This gives an idea of the number of disorders that can be triggered when calcium deviates from normal concentrations. A well-known example of the problems of below-optimal calcium concentrations in cows is post-calving hypocalcemia, it is however not the only potential health issue.

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A hand holding test tubes filled with blood
09 Jul
Hypocalcemia

Osteoclasts differentiation predicts risk of hypocalcemia in peri-parturient cows

Alvaro Garcia

Maintaining an adequate concentration of calcium in blood during the transition period is very important. The start of a new lactation challenges the cow’s ability to maintain normal blood calcium. Colostrum and milk are very rich in calcium, and cows must quickly adjust to these sudden losses. Second and greater lactation cows are generally more affected by this drastic calcium decline.

There is a subclinical form of hypocalcemia that can progress into the clinical form. In the subclinical form the signs are more subtle and difficult to detect, however the earlier its detection the greater the chances for a successful treatment. When a cow becomes recumbent, we are already likely in presence of clinical hypocalcemia.

The subclinical form predisposes to other metabolic diseases. Slight drops in blood calcium concentrations lead to reductions in feed intake, decreased smooth muscle (internal organs) tone, and increased incidence of retained fetal membranes, displaced abomasum, and mastitis. A critical step to maintain adequate blood calcium levels is to achieve an equilibrium between positive and negative ions. The balance between cations (positive charge) and anions (negative charge) should tend to neutrality.

What is the key to maintain blood calcium levels in dairy cows?

When considering close-up cow diets however it is recommended that the dietary ionic balance be negative (more anions than cations) because a negative balance leads to more calcium mobilization and absorption. Bone metabolic markers in blood have been used to monitor the adequacy of Ca mobilization in dairy cows during the transition period. One example is osteoprotegerin, an anti-resorptive protein that downregulates osteoclast differentiation in the bone.

Tartrate-resistant acid phosphatase (TRAP5b) secreted by the osteoclasts provides a good assessment of the number of these active cells present. Since osteoprotegerin downregulates the activity of osteoclasts, it is logical to expect that its concentration will be reduced at calving. The differentiation of the osteoclasts is triggered by calving and regulated by the inducer of its ligand called RANKL (nuclear activator NF-κB ligand) that acts as its inhibitor. From this perspective then the osteoprotegerin/RANKL ratio reflects the amount of bone resorption occurring and the amount of calcium in circulation.

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27 Feb
Hypocalcemia

Effects of subclinical hypocalcemia in Holstein cows

Lucas Pantaleon

The transition from late gestation to early lactation is a period of physiological adaptation for dairy cows because regulation of metabolic functions is paramount for normal parturition and lactogenesis. Pregnant cows feed intake decreases by 30% near parturition which restricts the intake of calcium (Ca), in turn the amount of Ca required per day triples during the first week of postpartum. Therefore, Ca regulation is vital to ensure life and milk production during this critical period in the production cycle of dairy cows.

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Risk factors associated with hypocalcemia in Jerseys
05 Sep
Hypocalcemia

Risk factors associated with hypocalcemia in Jerseys

Fernando Díaz

At calving, calcium requirements are quadrupled, which results in cows experiencing variable degrees of subclinical to clinical hypocalcemia. Subclinical hypocalcemia (SCH) is normally defined as calcium concentrations in blood lower than 2.1 mmol/L (8.5 mg/dL). Previous research conducted in Holsteins reported that number of lactations and prepartum calcium status were the most important factors associated with having SCH at parturition.

Cows in third or greater parities were 70% more likely to have SCH than second-lactation cows. Similarly, multiparous cows with low blood calcium levels in the prepartum period were 40% more likely to have SCH at parturition than cows with normal calcium concentrations. Jersey cows are more prone to SCH than other breeds, may be due to the greater calcium content in their milk and higher milk component production per unit of body weight.

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