With an estimated 10-11 million mules worldwide, they serve a necessary part of people’s livelihoods and the economy in many countries. To date, behaviors and reflexes during the peripartum period just after birth are well described for horses and donkeys, but not for mule foals. At the 2022 American Association of Equine Practitioners Convention held Nov. 18-22 in San Antonio, Texas, Claudia Barbosa Fernandes, DVM, MSC, PhD, of the University of Sao Paulo, Brazil, addressed this topic as one that is important for determining health or the presence of problems in newborn mule.
In her study, Barbosa Fernandes made comparisons between 17 horse and 30 mule foals. Significant differences she identified included:
- APGAR (appearance, pulse, grimace, activity, and respiration- parameters used to assess vitality in newborns) scores for mule foals were higher than for horses. The higher the number, the greater the newborn’s adaptation to the new environment outside the uterus.
- Mule foals are faster at initiating the suckle reflex, standing, and nursing than horse foals.
- Mares birthing mule foals eliminated the placenta faster than mares birthing horse foals – 35 minutes for mule-birthing mares compared to 113 minutes for horses.
- Meconium (the first manure) elimination in mule foals was substantially slower than for horse foals.
- Blood lactate levels in mule foals were lower at 720 hours after birth than horse foals.
- Blood glucose levels by 12 and 24 hours were higher in mule foals than horse foals.
In summary, Fernandes reported that mule foals have a more efficient adaptability after birth than horse foals, based on behavior and APGAR scores. Early in the days following birth, they have greater oxygen consumption, less anerobic metabolism, less lactate and less intracellular acidosis than horse foals. Adult horses and mules have no differences in these parameters.
She said a “hybrid vigor phenomenon” appears to be present in mule foals: Better performance than the parent; greater resistance to environmental factors like poor-quality nutrition and low water availability; greater agility; and quick adaptation to their environment.