Risk factors for abomasal volvulus and left abomasal displacement in cattle

A hospital-based case-control study was conducted to evaluate and compare risk factors for abomasal volvulus (AV) and left displaced abomasum (LDA) in cattle. Medical record abstracts were derived from 17 North American veterinary schools by the Veterinary Medical Data Program for all cattle admitted between Jan 1, 1977 and Dec 31, 1986, and for those with a diagnosis of AV or LDA. From a total of 108,956 individual cattle records, 1,036 cases of AV and 7,695 cases of LDA were identified, with a ratio of LDA to AV cases of 7.4 to 1. In-hospital mortality was 23.5% for AV and 5.6% for LDA. Age, breed, gender, and season each had significant (P < 0.05) effects on risk for AV and LDA. Risk for AV and LDA increased with increasing age, with greater risk in cattle aged 4 to 7 years. Dairy cattle were at higher risk of developing AV (adjusted odds ratio, 36.4) and LDA (adjusted odds ratio, 95.2) than were beef cattle. The odds of AV in Brown Swiss cattle were significantly (P < 0.0001) lower, and the odds of LDA in Guernsey cattle were significantly (P < 0.0001) higher than those in Holstein cattle. Female cattle were also at higher risk of developing AV (adjusted odds ratio, 3.3) and LDA (adjusted odds ratio, 29.1) than were male cattle. The odds of AV and LDA varied considerably throughout the year, with the lowest number of cases observed in autumn. Seasonal development of AV differed significantly (P < 0.0001) from that Of LDA, with the odds of AV and LDA being highest in January and March, respectively. The medical records for all cattle with AV and LDA examined at the teaching hospital over a 10- and 5-year period, respectively, were reviewed, and the time interval since parturition, as well as the existence and nature of concurrent disease, were recorded. Proportionately fewer cases of AV than LDA developed during the first 2 weeks after parturition (28.3% of AV cases vs. 57.0% of LDA cases). Concurrent disease existed in 30.4% of AV cases and 53.6% of LDA cases, with the rates of concurrent disease differing significantly (P < 0.0001) between the 2 groups. The misclassification rate for data generated at the teaching hospital was estimated to be 6.5% for AV and 5.3% for LDA. On the basis of the findings of this study, we hypothesize that: abomasal atony is a prerequisite for AV and LDA; existence of an abdominal void immediately after parturition facilitates development of AV and LDA; normal rumen volume provides a moderately effective barrier against LDA; risk of LDA does not increase appreciably with advancing pregnancy; and the direction of abomasal displacement (AV or LDA) after abomasal atony and dilation is influenced principally by rumen volume.