Foals born alive from mares with ultrasonographically assessed placental abnormalities: Neonatal health and development up to weaning compared to foals from healthy mares

Little is known about the health status of foals born alive from mares treated for placental disease. The aims of the present study were (1) to compare the neonatal health status and health development during the rearing period of foals born from mares treated for ultrasonographically assessed placental abnormalities (UPA) to age-matched healthy foals from the same warmblood stud and (2) analyze the influence of mare's placental health on colostrum quality. Foals (n = 127) born from mares with UPA (UPA group; P) in 2017-2019 were compared to 127 foals born from healthy mares (control group; C). Sixty-six UPA mares showed subclinical placental abnormalities (PSc1) and 61 mares showed clinical placental abnormalities (PSc2). The colostrum quality assessed by refractometry showed that healthy mares had 42 excellent (>30 %), 73 good (20-30 %) and 6 poor (<20 %) colostrum, whereas UPA mares showed 29 excellent, 66 good and 26 poor colostrum quality (P < 0.001). The administration of high-quality colostrum was more frequent in the UPA group (17.5 %) than in C (7.9 %; P = 0.024). The mean (±SD) gestation length of UPA mares was shorter (330 ± 11 days) and foal birth weight lower (54.2 ± 7.3 kg) compared to the healthy pregnancies (335 ± 11 days; P = 0.002 and 57.0 ± 6.6 kg; P < 0.001). The number of foals with a reduced immunoglobin G concentration 14 h postpartum was significantly higher in PSc2 (P = 0.007). Foals born from UPA mares received foreign plasma (P 25.4 % vs C 4.2 %; P = 0.028) more frequently. Premature placental separation, the occurrence of the retention of fetal membranes, placental weight, foal vitality and the white blood cell count did not differ between groups. Regarding the health status of the foal in the neonatal period (1-14 days postpartum), 10 foals (8.1 %) born from UPA pregnancies showed maladjustment syndrome, whereas none of the foals in the control group showed this condition (P < 0.001). Foals from UPA mares developed diarrhea more often (P 31.4 % vs C 19.9 %; P = 0.042), whereas omphalitis, pneumonia, sepsis, meconium obstipation and contracted tendons did not differ between the groups. Multimorbidity and treatment were more frequent in foals born from UPA pregnancies (P 12.8 % vs C 4.7 %; P = 0.004 and 59.6 % vs 40.4 %; P = 0.007). In conclusion, foals born alive from UPA mares face decreased immunity and an increased risk of disease during the first 14 days postpartum. The study underlines that colostrum supplementation from a healthy mare seems essential in UPA pregnancies.