Retrospective study of ten years of dystocic calving assisted by veterinarians in a bovine semi-extensive production grass-based system.

This retrospective study assessed dystocic calving attended by a group of veterinarians over a ten-year period (2014-2024) in the semi-extensive bovine production system of Terceira, Azores, where cows spend the majority of their time grazing year-round on inclined volcanic pastures, with a high degree of mobility. Data were collected from 3257 dystocic parturitions involving 3523 calves. The data presented here derive exclusively from records of one veterinary team and are not representative of all dystocia cases on the island, as other veterinarians and farmers also attended calving. Fetal causes were the most prevalent, particularly abnormal presentations, postures, and positions. Primiparous cows were proportionally more affected by fetopelvic disproportion (P < 0.001, OR = 3.67, [3.03-4.46]); incomplete vulvar dilation (P < 0.001, OR = 6.59, [4.40-9.87]); and incomplete cervical dilation (P < 0.001, OR = 3.88, [2.56-5.87]) and pluriparous cows were proportionally more affected by uterine torsions ((P < 0.001, OR = 2.12, [1.46-3.09]) and uterine inertia (P < 0.001, OR = 4.54, [3.27-6.31]). The calf mortality was lower in crossbreed calving (346/1053, 32.9%) than when cow and bull were of the same breed (810/2159, 37.5%), (P = 0.0098), with purebred calves having 1.2 higher odds of dying (OR = 1.2, [1.05-1,43]). Dystocia associated calf mortality reached 1400 out of 3523 (39.7%), with increased rates observed in twin births (71/133,53.5%), primiparous (427/888, 48.1%) and cases involving congenital malformations (53/62, 85,9%). Calf mortality in dystocic calving varied with season of calving (P = 0.04), with higher calf dystocia associated mortalities, in this group, in Autumn. The data indicates that the causes does not substantially differ from those reported in other systems.