By Maurice L. Eastridge
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 (provide links).
Another disorder that primarily occurs within the first two weeks after calving is displaced abomasum (DA). The abomasum is one of the four compartments to the ruminant stomach. It is referred to as the “true stomach”, is at the end of the four compartments, and lies just inside the abdominal cavity on the underside of the animal. There are three scenarios that possibly contribute to the abomasum not staying in place:
- 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) allows for organs to shift.
- The increase in concentrate in the diet to meet the increased energy demands of lactation, in conjunction with rumen papillae that are not very long from the cow having been on mostly a forage diet in the dry period, results on increased flow of volatile fatty acids to the abomasum which can reduce the motility of the abomasum.
- 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 on one another, with fresh cows can contribute to the risk for DA.
Cows with low dry matter intake, high body condition scores, and high concentrations of blood non-esterified fatty acids prepartum are at greater risk for a DA after calving. Intakes by cows are rather low at calving and when cows calve during the heat and humidity of the summer, intake after calving is even lower than cows calving in the fall and winter, which increases the risk for DA. The occurrence of DA in cows beyond 60 days in milk typically occurs due to 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 DA
About 80 to 90% of the cases of DA result when the abomasum moves upward on the left side of the animal. However, right displaced abomasum occurs and even a right torsed abomasum can occur but is rare (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 DA include reduced feed intake, reduced milk yield, reduced fecal excretion, and ketosis from lack of feed intake, but the definitive indication is the ping heard with a stethoscope when thumping the side of the animal. When the abomasum displaces, it fills with gas and the ping is from the thumping sounds bouncing back from the air-filled organ. Once diagnosed, a veterinarian can perform surgery or roll the animal to get the abomasum back in place.
Impact of DA
The primary costs associated with DA are 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 1200 lb less milk by cows with a DA from calving to 60 days after diagnosis of the 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. The risk of a cow being culled from the herd after experiencing a DA increases with lactation number and milk loss due to a DA increases with lactation number. The goal is for less than a 4% incidence of DA in a dairy herd.