The abomasum is the 4th stomach of ruminating animals. It is also called the “true” or “rennet stomach” and the ” reed”
Its is elongated, pear -shaped sac lying on the floor of the abdomen, on the right-hand side, roughly between the 7th and 12th ribs
Abomasal displacement is the most important disease complex associated with the abomasum in cattle.
The displacement is categorised as left-sided or right-sided, with some distinctions in the cause of the disease and therapy.
Left sided abomasal displacement is associated with a longer duration of disease, commonly occurs in the first 30 days of lactation and is often associated with metabolic or hepatic disease.
Right sided displacement is less common, can be associated with other gastro-intestinal disease and often presents as a more severe clinical condition.
The condition is commonly associated with high yielding, intensively fed dairy cows in late gestation or early lactation, but can be seen in intensive beef production as well. The lactational incidence of left sided abomasal is reported as 1.2% and right sided abomasal as 0,4% In the UK, the condition is most commonly seen as left sided abomasal, occurring sporadically in a dairy herd during the housing period in January-March.
Whilst the cause of the condition is not clearly established and is probably of a multiple nature, the following risk factors have been identified: high yielding cows, intensive concentrate feeding, late gestation or early lactation, changes in weather conditions, marked body condition score loss in the periparturient period, association with milk fever and poor dry cow management with not enough long fibre in the diet and no introduction to lactation period feeding before calving.
In Scandinavia, an association with high levels of root crops in the diet has also been made, particularly with right-sided displacement. It is believed that the soil on the root crops is the initial factor, causing ulceration of the stomach, leading to abomasal atony and displacement. An association with forestomach disorders, particularly foreign bodies (i.e. “wire”) in the rumen-reticulum, has been reported as well.
Organic farms are unlikely to experience problems with displaced abomasum, other than as sporadic cases secondary to milk fever or other disease. Outbreaks associated with soil-contaminated root crop feeding are a possibility on farms where fodder beet is used in large quantities.
However, one study indicated that herds that received fewer energy-rich carbohydrates in their diets than control herds experienced a higher incidence of displaced abomasum. Organic herds that have difficulties in meeting the energy requirements on home-grown diets immediately after calving might, therefore, be predisposed.
In cases of sporadic occurrence of abomasal displacement in a single cow, there is usually no need to change the existing feeding or management system.
An isolated case is most likely to be of a secondary nature, due to milk fever, disease of the uterus or another disease that causes abomasal atony.
If, however, one or several cases are diagnosed during consecutive housing periods, there is a need to investigate the potential causes of this, and improve feeding or management as needed.
The following measures have been recommended:
- Provision of adequate long fibre in dry cow diet (preferably hay)
- Provision of an adequate supply of palatable energy-rich carbohydrates in the diet, particularly immediately after calving
- Provision of adequate daily exercise for dry cows
- Gradual introduction of concentrates in the dry cow diet prior to calving (up to 2 kg /cow) but avoidance of “steaming up”
- Limited amount of maize silage to dry cows
- Avoidance of “peaking” the milk production in early lactation by increasing concentrate intake.
- Prevention of hypocalcaemia and ketosis in the periparturient period.
- Achieving the optimum body condition score at dry-off (2.5/5) and calving (2.5-3/5), to minimise condition score loss in the periparturient period to a maximum of 1 score (1-5 score).