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Neonatal development of the diaphragm of the horse, Equus caballus
M A Cobb1, W A Schutt, J L Petrie
1Department of Anatomy, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401.
Insights
Neonatal horse diaphragms differ from adults in fiber types and myosin. This suggests a slower maturation rate than other mammals, potentially explaining health issues in young horses.
Area of Science:
- Equine anatomy and physiology
- Comparative mammalian diaphragm development
Background:
- Neonatal equine diaphragms exhibit distinct histochemical and molecular profiles compared to adults.
- Understanding these differences is crucial for equine health and developmental biology.
Purpose of the Study:
- To investigate the developmental changes in diaphragm composition in horses from birth to seven months.
- To compare the maturation rate of equine diaphragms with other mammals.
Main Methods:
- Histochemical analysis of diaphragm fiber type composition.
- Myosin heavy chain and native myosin isoform analysis.
Main Results:
- Significant increases in Type I fibers with age were observed.
- Myosin isoform data indicate a slower maturation rate than hypothesized for ungulates.
Conclusions:
- Equine diaphragm maturation is slower than previously assumed, challenging the precocial maturation hypothesis for ungulates.
- Developmental differences may contribute to conditions like aspiration pneumonia in young horses.
Abstract:
The diaphragm of neonatal horses is significantly different from the diaphragm of adult horses in terms of histochemical fiber type composition, myosin heavy chain isoform, and native myosin isoform composition. There is a significant increase in the percentage of type I fibers present in the diaphragm with increasing age from birth through about seven months postnatal age. A possible lack of postural tone in the hiatal region of the neonatal diaphragm is suggested to account for increased incidence of vomiting or aspiration pneumonia in younger horses. The isoform data lead to rejection of the hypothesis that the diaphragm of the horse should, as an ungulate, be relatively precocial in its rate of maturation relative to other non-ungulate mammals that have been studied.