WITHDRAWN: Evaluation of two faecal occult blood diagnostic tests for detection of non-perforating abomasal lesions in cattle

Abstract

Non-perforating abomasal lesions have been observed with a high prevalence in slaughtered dairy cattle. Of all lesions found 62-66% were reported to be bleeding and 41-44% were reported to be chronic. The diagnostic properties of two faecal occult blood tests for detection abomasal lesions were evaluated. First, an in vitro titration test was used to determine the detection limit for blood in faeces for each of the tests. A tetramethylbenzidine-based test detected 2 ml blood and a guaiac-based test detected 4.5 ml of blood per 1,000 g faeces. Then, to determine if blood is degraded by rumen microbes, an in vitro study of blood fermentation in rumen fluid was conducted. Blood or haemoglobin in the quantities used did not break down when fermented for 48 hours. Lastly, faeces from 1,553 cattle was collected in a slaughterhouse and tested for the presence of blood the same day and 2 days after. The faecal results were compared with the presence of abomasal lesions in the cattle investigated. Cattle with ≥ 4 lesion subtypes considered to be bleeding had more positive test results. Cattle with ≥ 4 subtype Ib lesions had 1.7 times higher odds of testing positive in the tetramethylbenzidine test on Day 2 (95% confidence interval: 1.4 – 1.9) and cattle with ≥ 4 subtype Ic lesions had 1.9 times higher odds of testing positive (95% confidence interval: 1.6 – 2.3). However, 20% false-positive results were also observed, and a positive test can not necessarily be interpreted as the cow having abomasal lesions.