The majority of the health problems and associated veterinary costs for dairy cattle occur within the first 30 days of lactation. Management and feeding of the dry cow can have major implications on disease risk for dairy cows at calving. Adequate intakes of energy, fiber, protein, and certain minerals, especially calcium and those that affect calcium absorption and metabolism, are important in reducing the risk for metabolic diseases. Tips on feeding fresh cows for improved performance and reducing the risks for hypocalcemia, ruminal acidosis, and ketosis have been provided in other articles in the nutrition series.
Another disorder that primarily occurs within the first two weeks after calving is a displaced abomasum (DA). The abomasum is one of the four compartments of the ruminant stomach. It is referred to as the “true stomach” and lies just inside the abdominal cavity on the underside of the animal. Three scenarios possibly contribute to the abomasum becoming displaced:
- The cow loses about 10% to 12% of her body weight at calving due to the weight of the calf, placenta, and fluids. These losses in the abdominal cavity in conjunction with low dry matter intake (thus low rumen fill) allow for organs to shift.
- The increase in concentrate in the diet to meet the increased energy demands of lactation, in conjunction with rumen papillae associated with the cow’s recent mostly forage diet in the dry period, results in increased flow of volatile fatty acids to the abomasum, which can reduce its motility.
- Hypocalcemia, whether clinical (often 5% of cows) or subclinical (possibility as high as 50% on average), reduces the tone of smooth muscle which helps to hold the abomasum in place. All of these scenarios that typically occur, likely not independent of one another, with fresh cows can contribute to the risk for a DA.
Cows at greater risk for a DA after calving have low dry matter intake, high body condition scores, and high concentrations of blood non-esterified fatty acids prepartum. Rather low intake experienced by all cows at calving increases the risk for a DA. However, when cows calve during the heat and humidity of the summer, intake after calving is even lower than that of cows calving in the fall and winter.
A DA in cows beyond 60 days in milk typically occurs due to these factors:
- low rumen pH caused by change in forage quality or particle size,
- changes in diet formulation with inadequate fiber,
- change in personnel responsible for the feed mixing, or
- malfunction of the feed mixer or feed scales.
Diagnosis of a DA
About 80% to 90% of the cases of a DA result when the abomasum moves upward on the left side of the animal. However, right displaced abomasum occurs and even a rare right-torsed abomasum can occur (the abomasum floats up on the right side and then twists). This latter case is very serious in that blood supply becomes severely restricted to the abomasum.
Common symptoms of a DA include reduced feed intake, reduced milk yield, reduced fecal excretion, and ketosis from lack of feed intake, However, the definitive indication is the ping heard with a stethoscope when the side of the animal is thumped. When the abomasum displaces, it fills with gas, and the ping is from the thumping sounds bouncing back from the air-filled organ. Once the condition is diagnosed, a veterinarian can perform surgery or roll the animal to get the abomasum back in place.
Impact of a DA
The primary costs associated with a DA are from the loss of milk production. In a University of Guelph study, cows with a DA produced about 700 lb less milk during the lactation in which the DA occurred than cows not having experienced a DA. A Cornell University study revealed an even greater milk loss – about 1,200 lb less milk by cows with a DA from calving to 60 days after diagnosis of a DA.
Additional costs include the veterinary fees and other associated diseases (e.g., ketosis). In one study, 30% of the milk loss occurred prior to diagnosis of the disease; thus, early detection in very important. Both milk loss due to a DA and the risk of a cow being culled from the herd after experiencing a DA increase with lactation number. The goal is for less than a 4% incidence of a DA in a dairy herd.
Displaced abomasum is a common disease in dairy cattle, but with careful feeding and management, the incidence in a dairy herd can be kept below 5%. Feeding before calving to maintain a steady intake of a balanced diet to avoid a major decrease in intake and avoiding overconditioning greatly reduce the risk of a DA after calving. Providing a balanced diet (especially for fiber and energy) after calving and ample bunk and resting space will reduce the risk for a DA. When a DA occurs after 60 days in milk, it is best to review dietary fiber and particle size, proper operation of the feed mixer and scales, and feeding procedures by employees. Reducing the risk for a DA improves cow health and well-being, increases milk sold, and reduces veterinary costs.