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Real-time ultrasound measure of the fetal eye (vitreous body) for prediction of parturition date in small ponies.
Abstract: Ultrasonographic fetal eye measures have been used to estimate gestational age of the fetus in light horse mares. However, fetal eye measures have not been published for smaller pony breeds. This study was conducted to develop reference ranges for ultrasonographic measures of fetal eyes in small ponies for the purpose of predicting days before parturition (DBP) when breeding or ovulation dates are unknown. Twenty-three Shetland-type pony mares were studied across one (n = 10) or two (n = 13) gestations in 2004 (18 pregnancies) and 2005 (18 pregnancies). Measurements of fetal eyes were obtained during transrectal ultrasound examination. Examinations were conducted once monthly in a field situation beginning in December (2003) or August (2004) until mares foaled (March through July). The length (from sclera to sclera) and width (from retina to cornea) of the vitreous body were measured. For the 273 examinations in which gestation age was greater than 2 months, eye measures were obtainable in 248 (91%). Mixed-effects linear regression modeling was used to account for serial growth measures within pregnancy, repeated measurements across mares, and unbalanced study design. Independent variables evaluated included vitreous body length, vitreous body width, the ratio of length to width, parity, and mare height at the withers at parturition. Eye length was the best single predictor of days before parturition, with almost no additional predictive value of the other variables considered. Our resulting regression equation is: days before parturition=265.16-0.21*(vitreous body length in mm)(2). This study suggests that measure of the fetal eye is a practical on-farm procedure for estimating days before parturition in small ponies.
Publication Date: 2006-01-19 PubMed ID: 16426670DOI: 10.1016/j.theriogenology.2005.11.019Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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The research study investigates the use of real-time ultrasound to measure the size of the fetal eye (specifically the vitreous body) in small ponies, which can be used to predict their parturition date. This method offers a practical on-farm solution to estimate days before parturition in the absence of known breeding or ovulation dates.
Study Overview
- This study is aimed to provide reference ranges for the ultrasonographic measurements of fetal eyes in small-sized ponies, a metric that is not yet known for this breed.
- Twenty-three Shetland-type pony mares were observed over one or two gestations in 2004 and 2005.
- Measurements of the fetal eyes’ lengths and widths were obtained through transrectal ultrasound examinations on a monthly basis until the mares gave birth.
- This measurement focused on the vitreous body of the eye – the ‘length’ from sclera to sclera (the white part of the eye), and the ‘width’ from retina to cornea (back to front of the eye).
Methodology and Results
- Out of all the examinations performed (273 of them), eye measures could be taken in 91% of the cases where gestation was over two months.
- Mixed-effects linear regression modeling was used to account for the growth measures within the pregnancy, repeated measurements across different mares, and unbalanced study design.
- To predict the number of days before parturition, independent variables like vitreous body length and width, the ratio of length to width, the number of births a mare has had (parity), and the mare’s height at the withers (shoulders) at parturition were considered.
- The length of the eye was found to be the best single predictor of the days before parturition, rendering almost no additional predictive value to the other variables evaluated.
- Based on this finding, the regression equation to predict days before parturition is given by: 265.16-0.21*(vitreous body length in mm)(2).
Conclusion
- This study proposes that using ultrasounds to measure the size of the fetal eye of small ponies could be a practical procedure to estimate the delivery date of these animals.
- These findings may be particularly useful in situations where the exact dates of breeding or ovulation are unknown.
Cite This Article
APA
Turner RM, McDonnell SM, Feit EM, Grogan EH, Foglia R.
(2006).
Real-time ultrasound measure of the fetal eye (vitreous body) for prediction of parturition date in small ponies.
Theriogenology, 66(2), 331-337.
https://doi.org/10.1016/j.theriogenology.2005.11.019 Publication
Researcher Affiliations
- Section of Reproductive Studies, University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, 382 West Street Road, Kennett Square, 19348, USA. rmturner@vet.upenn.edu
MeSH Terms
- Animals
- Embryonic Structures / diagnostic imaging
- Female
- Gestational Age
- Horses / embryology
- Parity
- Parturition
- Predictive Value of Tests
- Pregnancy
- Reference Values
- Time Factors
- Ultrasonography, Prenatal / methods
- Ultrasonography, Prenatal / standards
- Ultrasonography, Prenatal / veterinary
- Vitreous Body / anatomy & histology
- Vitreous Body / diagnostic imaging
Citations
This article has been cited 6 times.- Gao Y, Hannan MA, Murata K, Rajabi-Toustani R, Nambo Y. Ultrasonographic examination of equine fetal growth parameters throughout gestation in pony for Equine-Assisted Therapy. J Vet Med Sci 2022 Jan 7;84(1):74-81.
- Vieira GS, Paludo GR, Ramos AF, Pivato I, de Oliveira RA. Fetal development and blood hematological-biochemical parameters in Campeiro and Pantaneiro foals. Anim Reprod 2018 Aug 16;15(1):39-44.
- More S, Bicout D, Botner A, Butterworth A, Calistri P, Depner K, Edwards S, Garin-Bastuji B, Good M, Gortazar Schmidt C, Michel V, Miranda MA, Saxmose Nielsen S, Velarde A, Thulke HH, Sihvonen L, Spoolder H, Stegeman JA, Raj M, Willeberg P, Candiani D, Winckler C. Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses). EFSA J 2017 May;15(5):e04782.
- Valentini S, Castagnetti C, Musella V, Spinella G. Assessment of intraocular measurements in neonatal foals and association with gender, laterality, and body weight: a clinical study. PLoS One 2014;9(10):e109491.
- Murase H, Endo Y, Tsuchiya T, Kotoyori Y, Shikichi M, Ito K, Sato F, Nambo Y. Ultrasonographic evaluation of equine fetal growth throughout gestation in normal mares using a convex transducer. J Vet Med Sci 2014 Jul;76(7):947-53.
- Ali A, Derar DR, Alaeyeari AA, Alharbi YM. Fetometry in Arabian horses. Front Vet Sci 2025;12:1689769.
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