Characteristics of milk ejection, associated intramammary pressure changes and oxytocin release in the mare.
Abstract: The neuroendocrine reflex theory of milk ejection was investigated in the horse under natural suckling conditions. To this end 12 lactating mares were provided with acute jugular catheters and with intramammary pressure (IMP) recording catheters. The foal had free access to the contralateral mammary complex. Intramammary pressure could thus be recorded while blood was drawn simultaneously for oxytocin analysis from the undisturbed animal. Suckling periods associated with a characteristic increase in IMP lasted significantly longer than unsuccessful nursing attempts. Elements of successful sucklings involved physical stimulation of the mammary gland, a quiet phase and a sudden increase in IMP. Successful suckling took place at about 20-min intervals with a wide range from less than 5 min to greater than 100 min. Between 5 and 10 mU oxytocin i.v. were sufficient to evoke an increase in IMP identical in shape and duration to a naturally induced increase in IMP. Mean peak oxytocin levels reached 15.8 pmol/l plasma, with a maximal release of 39 pmol/l. In the majority of cases (greater than 80%) peak oxytocin release did not occur until after the increase in IMP; in some cases an oxytocin surge was not detectable at all, despite a milk ejection-associated increase in IMP. In three cases increase in IMP could be observed while the foals were away from the mother with no signs of any intention to suckle. The data indicate that in the horse some elements of the neuroendocrine reflex, such as tactile stimulation of the teat and a surge of oxytocin before an increase in IMP, are facultative and not essential for normal milk ejection.
Publication Date: 1988-11-01 PubMed ID: 3199055DOI: 10.1677/joe.0.1190219Google Scholar: Lookup
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- Journal Article
Summary
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This research investigates the complex process of milk ejection in lactating horses, examining the role of oxytocin and intramammary pressure in this process. The study found that the suckling stimulation of the mammary gland and an oxytocin surge are not essential prerequisites for successful milk ejection.
Objective of the Study
- The study aimed to investigate the neuroendocrine reflex theory of milk ejection under natural suckling conditions in horses. The researched examined the role of intramammary pressure (IMP) changes and oxytocin release in the milk ejection process.
Research Methodology
- The researchers monitored 12 lactating mares, installing acute jugular catheters for blood drawing and intramammary pressure recording catheters. The foals had free access to the contralateral mammary complex.
- The researchers measured oxytocin levels in blood samples drawn during suckling while simultaneously recording intramammary pressure.
Findings of the Study
- Suckling periods involving a characteristic increase in IMP were significantly longer than unsuccessful nursing attempts. Moreover, physical stimulation of the mammary gland, a quiet phase, and a sudden increase in IMP were key elements of successful sucklings.
- Successful suckling usually occurred at intervals of around 20 minutes, but could vary from less than 5 minutes to more than 100 minutes.
- Oxytocin release was not always initiated before an increase in IMP. In some cases, the researchers were unable to detect an oxytocin surge, despite an increase in IMP associated with milk ejection.
- In three instances, an increase in IMP was observed even when the foals were away from the mares and showed no intention to suckle.
Conclusion of the Study
- The findings suggest that elements like physical stimulation of the teat and an oxytocin surge, which are part of the neuroendocrine reflex, are not absolute necessities for successful milk ejection in horses. This suggests that the process of milk ejection in horses might be more complex and not fully reliant on the established neuroendocrine reflex theory.
Cite This Article
APA
Ellendorff F, Schams D.
(1988).
Characteristics of milk ejection, associated intramammary pressure changes and oxytocin release in the mare.
J Endocrinol, 119(2), 219-227.
https://doi.org/10.1677/joe.0.1190219 Publication
Researcher Affiliations
- Station de la Physiologie de la Reproduction (INRA), Centre de Tours, Monnaie, France.
MeSH Terms
- Animals
- Female
- Horses / physiology
- Lactation
- Litter Size
- Mammary Glands, Animal / physiology
- Milk Ejection
- Oxytocin / metabolism
- Oxytocin / pharmacology
- Pregnancy
- Pressure
- Time Factors
Citations
This article has been cited 3 times.- Mota-Rojas D, Marcet-Rius M, Domínguez-Oliva A, Martínez-Burnes J, Lezama-García K, Hernández-Ávalos I, Rodríguez-González D, Bienboire-Frosini C. The Role of Oxytocin in Domestic Animal's Maternal Care: Parturition, Bonding, and Lactation. Animals (Basel) 2023 Mar 30;13(7).
- Fabris G, Lucantonio A, Hampe N, Noetzel E, Hoffmann B, DeSimone A, Merkel R. Nanoscale Topography and Poroelastic Properties of Model Tissue Breast Gland Basement Membranes. Biophys J 2018 Nov 6;115(9):1770-1782.
- Leng G, Sabatier N. Measuring Oxytocin and Vasopressin: Bioassays, Immunoassays and Random Numbers. J Neuroendocrinol 2016 Oct;28(10).
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