The transition period after calving and returning to the milk parlor is the most critical time in the life of a dairy cow.
During this time her metabolism is under severe stress to meet the high nutrient demand for milk production. Because of the stress and nutrient demand, she is most susceptible to some diseases and metabolic disorders such as milk fever, retained placenta, Das, and mastitis.
At calving time, the start of lactation provides many challenges to the cow’s calcium levels. During her dry period, calcium is a requirement for fetal development, but with the onset of lactation, her calcium requirement doubles for colostrum and milk production. When there is not enough blood calcium, the body begins to draw on the calcium reserves stored in the bones.
Here are some of the health conditions impacting newly freshened cows and preventative measures and treatment:
Hypocalcemia: Calcium plays a important role in skeleton tissue, smooth muscle, nerve function and immune function. When we lose homeostatic function of calcium, hypocalcemia, or milk fever, occurs. Hypocalcemia is defined as total blood calcium levels falling below 5.0 mg/dL. Clinical signs are staggering, cold ears and lying in head-tuck position. Three stages include:
- Stage 1: Early signs of milk fever without going down.
- Stage 2: Cows that are down but not flat on their side.
- Stage 3: Cows lying flat and severely depressed.
Based on 2007 NAHMS Dairy Survey, five percent of cows will have clinical hypocalcemia. Prevalence of hypocalcemia is higher in Jersey and Guernsey breeds, and in older and/or higher producing cows.
Subclinical hypocalcemia: Subclinical hypocalcemia occurs when total blood calcium levels fall under 8.5 mg/dL. Subclinical hypocalcemia occurs without outward clinical, signs making it difficult to detect.
Recent data shows nearly half (47 percent) of lactating dairy cows are affected by subclinical milk fever at freshening. Even with anionic salt supplementation in the prefresh period, subclinical milk fever may still occur in 15 to 25 percent of cows at calving. Even though each case of subclinical hypocalcemia is $125 as compared to $300 per clinical case, subclinical hypocalcemia is much more expensive in the long run due to the number of animals impacted.
Prevention of subclinical hypocalcemia and hypocalcemia generally occurs through modifications to the pre-fresh or close-up diets. These changes allow for the physiological system which mobilizes calcium to be primed and ready for the increased demand for calcium associated with colostrum and milk production.
Options include:
- Low calcium diets pre-fresh
- Low potassium forages and/or diets pre-fresh
- Feeding anionic salts
- Supplementary Mg
Based on recent research from UW-School of Veterinary Medicine, Dr. Gary Oetzel recommends the following treatment and prevention practices:
Stage 2 or Stage 3 (down cow):
- Treatment is intravenous calcium to administer calcium rapidly. Oral calcium should not be given as smooth muscle tissue will be impacted making it difficult for the cow to swallow.
- To reduce risk of relapse, provide oral calcium once the cow is alert and able to swallow.
- Provide a second dose of oral calcium approximately 12 hours later.
Stage 1 (early signs of milk fever but still standing):
- Oral administration of calcium. Cows will absorb oral calcium rapidly and sustain blood calcium levels for 4 to 6 hours, peaking calcium levels within 30 minutes.
Strategic use of oral calcium boluses (one dose followed by second dose approximately 12 hours later):
- Early Stage 1 milk fever cases. Cold ears, wobbly, tricep tremors, poor GI. One dose now, one dose 12 hours later.
- After successful IV treatment of down cows. One dose after cow is up, alert and swallowing. An additional dose 12 hours later.
- Off feed early lactation cows.
- Herds who tend to treat hypocalcemia, have Jerseys, or do not utilize anionic salts in the pre-fresh diet.
- Herds without clinical signs should provide oral calcium to lame cows and previous high lactating milk cows.