Milk fever is a disorder affecting about 6 percent of dairy cows each year in the United States. Subclinical milk fever, defined as blood calcium (Ca) concentration falling below 8 milligrams per deciliter (mg/dl), occurs in up to 50 percent of older cows during the days immediately following calving. The decline in blood calcium concentration near calving represents a breakdown in the calcium homeostatic mechanisms of the body. Blood Ca in the adult cow is maintained around 8.5 to 10 mg/dl. There are 3 grams Ca in the plasma pool and only 8 to 9 grams Ca in all the extracellular fluids (outside of bone) of a 1,300-pound cow. The fluid within the canaliculi of bone may contain another 6 to 15 grams Ca; the size of this Ca pool being dependent on the acid-base status of the animal (larger during acidosis and smaller during alkalosis).

So often in veterinary medicine, as in other medical fields, we are looking for diagnostic tests to aid in treatment and to prognosticate for various diseases. Both infectious and noninfectious diseases may be diagnosed by detecting the causative agent, clinical signs, pathological changes, biochemical changes or surrogate evidence of past or present exposure to an agent (antibody).

What causes calf scours? As new calves arrive, so does the threat of the common condition known as calf scours or neonatal calf diarrhea.

The goal for management when feeding dairy replacement heifers is to produce high-quality replacement heifers at a low cost. It is difficult to detail all of the business and biological aspects of developing information-based quality control management programs for dairy replacements in this article; therefore, the following key control points will be offered.

Cow comfort has a direct impact on daily health and milk production. Rick Grant and other scientists at the Miner Institute in New York have studied the daily routine of high-producing dairy cows housed in a freestall barn. By combining this information with what we know about improving cow comfort, we can better manage our herds to improve profitability.

It is always easier to achieve a goal when working with biology, rather than against it. By taking advantage of important characteristics of bacterial growth, we can better achieve our goal of feeding clean colostrum.

Diseases caused by mycoplasma continue to emerge and remain frustrating to all segments of the dairy industry. In cows, several species of mycoplasma can cause mastitis, pneumonia, arthritis, abortion, and other disease syndromes. Mycoplasma bovis is the most common cause of mycoplasma mastitis and is one of the leading causes of contagious mastitis. In young stock, mycoplasma may cause a variety of disease syndromes as early as two to three weeks after birth.

Treatments for diarrhea caused by disease-causing organisms is a big deal to all calf raisers. It seems that we spend a tremendous amount of our time dealing with baby calves, working to feed them appropriate amounts of colostrum, keeping them isolated from organisms that may cause scours and, occasionally, treating those that do develop disease.

Reporting from Bagram, Afghanistan . . .

Severity of heat stress is quantified using a temperature humidity index (THI). Both ambient temperature and relative humidity are used to calculate a THI. Signs of heat stress become evident in dairy cows when the THI exceeds 72. The same THI can be produced by various combinations of temperature and humidity (see Figure 1). Dairy producers can purchase a thermometer or hygrometer and use Figure 1 to determine the level of heat stress at different locations on the dairy. Measurements should be taken at the level of the cows’ backs, along the feeding area, in the freestalls and in the holding pen.