Apparent Ca Test Positivity and Crossmatch Reactivity in Donkeys from Italy: Intraspecies and Horse–Donkey Compatibility

Abstract

Blood group distribution and serological compatibility are poorly characterized in donkeys. We estimated the apparent Ca positive-test frequency in 84 domestic donkeys and assessed donkey–donkey and horse–donkey crossmatch reactivity. Ca typing was performed using a commercial equine immunochromatographic assay. For donkey–donkey crossmatching, one major and one minor crossmatch were analyzed for each of the 77 Ca-concordant and 34 Ca-discordant pairs. Fifty-six of eighty-four donkeys yielded a positive result with the equine Ca assay (66.7%; 95% CI, 56.1–75.8%). Major combined macroscopic/microscopic reactivity occurred in 18/77 Ca-concordant and 11/34 Ca-discordant pairs, whereas minor combined reactivity occurred in 21/77 and 8/34 pairs, respectively. In crossed random-effects logistic models, the adjusted odds ratios for Ca-discordant versus Ca-concordant pairs were 1.56 (95% CI, 0.64–3.82) for major combined reactivity, 0.82 (95% CI, 0.32–2.10) for minor combined reactivity, and 1.57 (95% CI, 0.41–5.94) for major macroscopic reactivity; the minor macroscopic model was not estimable. Horse–donkey reactions were frequent and direction-dependent. When donkey plasma was tested against horse RBCs, combined reactivity occurred in 80/80 tests in the horse-donor/donkey-recipient dataset and in 76/76 tests in the reciprocal dataset, with macroscopic reactivity in 77/80 (96.3%) and 74/76 (97.4%), respectively. In the reciprocal horse-plasma/donkey-RBC direction, combined reactivity occurred in 53/80 (66.3%) and 51/76 (67.1%) tests, with macroscopic reactivity in 32/80 (40.0%) and 32/76 (42.1%), respectively. Ca concordance was not significantly associated with crossmatch reactivity in the present dataset, and Ca status alone did not account for the observed crossmatch-reactivity pattern.

The authors' abstract, as published at the source. Animals, 2026 · DOI ↗