Outbreak of Rickets in Pigs in the West of Santa Catarina

Abstract

Background: Rickets is a deficiency pathology that occurs in young and growing animals, leading to deficient bone mineralization. Rickets has been reported in several species producing numerous economic losses. The disease is caused by nutritional imbalance of calcium (Ca), phosphorus (P) and vitamin D. The aim of this work was to report two outbreaks of rickets in commercial weaning farms in the Seara city, in the western region of Santa Catarina State (SC), Brazil.Case: In August 2016, the Veterinary Pathology Laboratory (LPV) at the Concórdia Campus of the Catarinense Federal Institute (IFC) diagnosed two outbreaks of rickets in pigs in the weaning phase in Seara, SC. The clinical history was obtained by interviewing the field veterinarian and the farmers. In the anamnesis, both pig farmers stated having used a feed premix product from the same company, starting three months ago, and after that the pigs presented clinical signs of posterior paralysis and progressive weight loss. Six animals were submitted to necropsy and organs were collected from the abdominal and thoracic cavities; central nervous system and bones; fixed in 10% buffered formalin, routinely processed, paraffin embedded and stained with hematoxylin and eosin (HE) for histopathological analysis. Bone specimens were decalcified in nitric acid working solution 20 times their volume, during 5 days. In addition, samples of the premix product containing minerals and vitamins were sent to a specialized laboratory to analyze macroelements levels through the atomic absorption methodology. In property 1, there was a batch of 100 animals, the morbidity rate was 15% and lethality was 5%. In property 2, among 30 animals, the morbidity and lethality rate were 33%. Five animals from property 1 and one animal from property 2 underwent necropsy, that showed severe bone fragility and flexibility (6/6), growth plate discontinuity (2/6), as well as, increased volume of costochondral joints (rachitic rosary) and epiphyseal cartilage thickening (2/6). Regarding the premix used in both farms, the label showed manufactured guarantee of 110 g/kg of Ca (minimum), 62 g/kg of total P and 38,400 I.U./kg of vitamin D. Meanwhile the analysis of the product used in the feed mixture quantified 74.3 g/kg of Ca (minimum), 22.2 g/kg of total P and 40,098.9 I.U./kg of vitamin D. The diagnosis of rickets was established through the association of history, clinical signs, macroscopic, microscopic lesions and nutritional analyses.Discussion: The affected pigs weighed approximately 20 kg and consumed an average of 1.0 kg of feed per day. The recommended amount of feed consumption for pigs at this stage is approximately 953 g in American literature, while national recommendations described a consumption of 1,036 g/animal. Comparing information in the product label and laboratory analyses, the real level of Calcium was 32.4% (35.6 g/kg) lower in the product, as well as total Phosphorus level, 64.2% (39.8 g/kg) lower. On the other hand, Vitamin D levels were 4.4% (1,698.9 I.U.) above guarantee provided by the company. It is concluded that rickets in pigs raised intensively occurred due to non-observance of the minimum intake levels of Ca, P and Vitamin D in the diet. Although this is an evident conclusion, taking into account the industry's technification in Brazil, error in the formulation of the diet leading to animal mortality and serious economic losses to farmers should not be expected.