Hypovitaminosis A in extensively grazed beef cattle

• Published in: Australian veterinary journal Vol. 95; no. 3; pp. 80 - 84
• Main Authors: Parker, EM, Gardiner, CP, Kessell, AE, Parker, AJ
• Format: Journal Article
• Language: English
• Published: Melbourne Wiley Publishing Asia Pty Ltd 01-03-2017; Wiley Subscription Services, Inc
• Subjects: Animal Husbandry; Animals; Astrebla; Cattle; Cattle Diseases - diagnosis; Cattle Diseases - epidemiology; cattle medicine; Diagnosis, Differential; Droughts; nutritional disease; Queensland - epidemiology; ruminant nutrition; Vitamin A; vitamin A deficiency; Vitamin A Deficiency - diagnosis; Vitamin A Deficiency - epidemiology; Vitamin A Deficiency - etiology; Vitamin A Deficiency - veterinary; Vitamin deficiency; nutritional disease; ruminant nutrition; vitamin A deficiency; cattle medicine
• ISSN: 0005-0423; 1751-0813
• DOI: 10.1111/avj.12560

Case report
Vitamin A deficiency was diagnosed in a herd of 97 19‐month‐old Braford heifers in the Mitchell Grass Downs (Astrebla spp.) bioregion of Hughenden in north‐western Queensland during November 2015. Two heifers died after a 48‐h history of sternal recumbency and of the 19 that had neurological signs, 7 were blind. Histological changes in the optic nerves of the two necropsied cattle were consistent with vitamin A deficiency. This diagnosis was supported by vitamin A concentrations in fresh liver samples of 5 and 6 mg/kg wet tissue (reference range, 100–175 mg/kg) despite treatment of the cattle with twice the recommended dose of parenteral vitamin A 3 weeks prior to sampling. Rainfall on the property during the 2 years before the outbreak was less than the annual rainfall average of 464 mm, with a total of 281 mm in 2014 and 117 mm from January to November in 2015, most of this falling in January.
Conclusion
Plant assays for both β‐carotene and crude protein concentrations in dry matter (DM) were less than the recommended dietary requirements for beef cattle (0.30 mg/kg DM and 56 g/kg, respectively).