Cows with subclinical hypocalcaemia (SCH) are rarely easy to identify. Yet this invisible health challenge causes serious issues on dairies.
Cows with SCH do not show clinical symptoms, but have a low blood concentration of calcium below a still-undefined critical threshold. This level has not yet fallen low enough to cause clinical milk fever, but it’s low enough to cause health and production challenges for the cow.
SCH impacts a significant number of cows in herds all across the country. The National Animal Health Monitoring System (NAHMS) estimates as many as 54% of multiparous cows and 25% of first-calf heifers succumb to SCH, even though clinical cases of hypocalcaemia are much lower overall and almost absent from first-calf heifers.
An even bigger issue is that SCH negatively affects immune function, production performance and reproductive function. It also increases the risk for postpartum metabolic diseases. Therefore, it’s critical that you take steps to reduce the risk of SCH within your herd and address underlying causes to protect animal performance and your dairy’s profitability.
Manage for Improvement
There are a couple of fundamental practices that you should implement to minimize incidence of SCH. These include:
- Clearly define and record transition cow events. This includes difficult calvings, retained placentas, ketosis, metritis, mastitis and start-up milk production. Use this information to establish a baseline for herd monitoring.
- Test forages using wet chemistry: Analyze forages and byproduct commodity feeds for sodium, potassium, chloride and sulfur by wet chemistry analysis.
- Formulate the prepartum ration for a DCAD of -8 to -12 meq/100g dry matter. This practice is proven to adequately acidify cows and help reduce the risk of clinical milk fever and SCH postpartum. As a result, more of the total blood calcium becomes available in ionized form, which reduces the risk of SCH and milk fever. Identifying the right anion source to lower DCAD while also delivering metabolizable protein (MP) is critical as you formulate prepartum rations.
- Monitor urine pH. Urine pH serves as a reflection of blood pH, which assesses the implementation of the negative DCAD ration. Take urine samples from cows that have been fed the close-up diet for at least five days. Consistentlcollect samples at the same time postfeeding, recognizing that urine pH will vary during the day. Target the following urine pH levels:
![urine_pg[1]](https://www.thebullvine.com/wp-content/uploads/2015/03/urine_pg1-600x228.jpg)
Remember that the benefit of carefully formulated, negative DCAD close-up diets relies on cows consuming this diet—and consuming it for an adequate amount of time.
Management factors including stocking density, cow comfort, bunk space, water quality and availability, and heat abatement will all impact ration effectiveness—and can impact SCH incidence in your herd. Take measures to ensure that cows are not limited by any of these considerations.
By Dr. Joel Pankowski, manager, field services, Arm & Hammer Animal Nutrition
