Hypovitaminosis A in extensively grazed beef cattle
2017
Parker, EM | Gardiner, CP | Kessell, AE | Parker, AJ
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).
显示更多 [+] 显示较少 [-]