A Prospective Exploratory Study on Potential Systemic Causes and Risk Factors for Subconjunctival Bleeding in Neonatal Calves

Subconjunctival bleeding in neonatal calves is most commonly seen in association with birth trauma. There are currently no investigations available that examine the systemic causes of this phenomenon. In this prospective and exploratory case-control study, seven out of eighty neonatal calves examined over a two-year period were born with subconjunctival bleeding. The anatomical location of the subconjunctival bleeding and details related to the cow's and calf's parturitional and gestational history were recorded. Blood samples from cases and controls (<i>n</i> = 7) were analyzed hematologically, and the serum lysyl oxidase-like enzyme 4 (LOXL4) concentration was determined through an ELISA to establish evidence for possible structural, copper-dependent vascular abnormalities. We found no significant difference in the clinical data of both groups. Hematological examinations revealed no evidence of anemia or thrombocytopenia. Additionally, no significant differences in differential leukocyte counts were observed between the different groups. However, the neutrophil-lymphocyte ratio (NLR) demonstrated a significant difference between the calves with subconjunctival bleeding and controls. The serum LOXL4 protein concentration was not significantly different in calves with subconjunctival bleeding compared to controls. In conclusion, our clinical, hematological, and biochemical data provided no evidence for potential systemic causes of subconjunctival bleeding. However, these results must be considered in light of this study's small sample size and thus low statistical power.