Endocrine profiles of periparturient mares and their foals 1 E. L. Berg, D. L. McNamara, and D. H. Keisler 2 Division of Animal Sciences, University of Missouri, Columbia 65211 ABSTRACT: The aim of this study was to character- ize concentrations of leptin, IGF-I, and thyroid stimu- lating hormone (TSH) in the blood serum of mares pre- and postpartum, in the milk serum of mares postpar- tum, and in the blood serum of their foals. Nine preg- nant Quarter Horse mares and their offspring were used in this study. Once weekly between 1000 and 1200 h for 2 wk before their predicted parturition date, mares were weighed, assigned a BCS, and blood was sampled via jugular venipuncture. Within 2 h of parturition and before the foals nursed (d 0), blood samples were ob- tained from the mares and foals, and a milk sample was collected from the mares. Blood from the foals and blood and milk from the mares were collected again at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 12, 19, 26, 33, and 61 d postpartum. Mares and foals also were weighed and assigned a BCS on d 0, 5, 12, 19, 26, 33, and 61. Addi- tionally, on d 5, 33, and 61, ultrasound images of fat depth and area of the LM immediately cranial to and parallel with the last rib on the left side of the foals were measured to characterize changes in fat depth and LM area over time. There were no changes in mare blood concentrations TSH (P = 0.15), nor were there Key words: foal, insulin-like growth factor-1, leptin, mare, milk, thyroid stimulating hormone ©2007 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2007. 85:1660–1668 doi:10.2527/jas.2006-771 INTRODUCTION Successful transition of the animal from the fetal to the neonatal state involves tremendous physiological ad- aptations on the part of the neonate and the dam. The success or failure of this transition process equally dic- tates the survival of the offspring and subsequent recov- ery of the dam. Various hormones and growth factors present in colostrum and milk of many species may serve to program the endocrine system of the neonate in the acute postpartum period and therefore shape the re- 1 The authors thank M. Ellersieck for assistance with statistical analysis. 2 Corresponding author: KeislerD@missouri.edu Received November 22, 2006. Accepted April 5, 2007. 1660 any changes in foal blood concentrations of leptin (P = 0.54) or TSH (P = 0.10) during the trial period. Mare blood concentrations of IGF-I tended to change over time (P = 0.07), whereas leptin changed over time (P < 0.001), initially decreasing and then remaining rela- tively stable after d 5. Foal blood concentrations of IGF- I increased initially, peaked at d 19, and stabilized thereafter (P < 0.001). Milk concentrations of leptin and TSH were greatest on d 0 and decreased over time (P < 0.007), reaching nadir concentrations at d 61. Milk concentrations of IGF-I also changed over time (P = 0.02), being greatest on d 0 and undetectable by d 12. There was no difference in BCS (P = 0.94) in mares over time, but there was a difference between pre- and postpartum BW (P < 0.001) due to foaling. However, no differences were detected in pre- (P = 0.70) or post- partum BW (P = 0.76) of mares over time. Mean ultra- sonic fat depth and LM area increased (P < 0.04) as the foals aged, as did BCS and BW (P < 0.001). Recognizing changes in metabolic hormones surrounding the time of parturition in the mare and foal provides a basis for further determination of the role, if any, these hor- mones play in the milk, as well as in the neonate. sponse of the body to feeding and stress later in life (de Moura and Passos, 2005). Identification and elucidation of the roles of various milk compounds passed to the newborn may provide insight into the development of obesity-related maladies in horses. Hormones previously identified in mares’ milk include insulin, IGF-I (Hess-Dudan et al., 1994), leptin (Salimei et al., 2002; Romagnoli et al., 2006), progesterone (Laiti- nen et al., 1981), and triiodothyronine (S ´ lebodzin ´ ski et al., 1998). However, limited information is available on acute changes in metabolic hormones relative to parturi- tion in mares and their foals. Therefore, our objective was to characterize some of the endocrine changes occurring in periparturient mares and their offspring. We quantified concentrations of lep- tin, IGF-I, and thyroid stimulating hormone (TSH) in the blood serum of mares pre- and postpartum, in the milk serum of lactating mares postpartum, and in the Published December 8, 2014