Domestic Animal Endocrinology 35 (2008) 325–342 Available online at www.sciencedirect.com Review The role of endocrine insulin-like growth factor-I (IGF-I) in female bovine reproduction M.A. Velazquez a,* , L.J. Spicer b , D.C. Wathes c a Escuela Superior de Ciencias Agropecuarias, Universidad Autónoma de Campeche, Calle 53 s/n, C.P. 24350, Escárcega, Campeche, Mexico b Department of Animal Science, Oklahoma State University, Stillwater, OK 74078, USA c Reproduction, Genes and Development Group, Department of Veterinary Basic Sciences, Royal Veterinary College, London AL9 7TA, UK Received 11 April 2008; received in revised form 10 July 2008; accepted 14 July 2008 Abstract Insulin-like growth factor-I (IGF-I) plays a pivotal role in cattle fertility, acting as a monitoring signal that allows reproductive events to occur when nutritional conditions for successful reproduction are reached. However, endocrine IGF-I is not a predictor of reproductive events, but rather an indirect estimator of the suitability of the animal to achieve the reproductive event in question. Although measuring circulating IGF-I concentrations might not have any clinical application in the cattle industry, endocrine IGF-I screening will continue to be important for the study of interactions between nutrition and reproduction. In addition, endocrine IGF-I screening could be used as an ancillary test for the selection of cattle for high reproductive potential, especially in herds of high genetic merit for milk production, in which a decline in fertility has been identified. © 2008 Elsevier Inc. All rights reserved. Keywords: Endocrine IGF-I; Reproduction; Nutrition; Cause–effect relationship; Cattle Contents 1. Introduction ............................................................................................... 325 2. Endocrine versus paracrine–autocrine IGF-I action in cattle reproduction ........................................ 326 3. Endocrine IGF-I during puberty ............................................................................. 327 4. Endocrine IGF-I during the estrous cycle ..................................................................... 328 5. Endocrine IGF-I during pregnancy in cattle .................................................................. 329 6. Endocrine IGF-I during the postpartum period in cattle ........................................................ 331 7. Usefulness of endocrine IGF-I profiles ....................................................................... 333 8. Conclusions ............................................................................................... 334 References ................................................................................................ 334 * Corresponding author. Tel.: +52 9828241421; fax: +52 9828241421. E-mail address: lestaurus 18@hotmail.com (M.A. Velazquez). 1. Introduction Reproduction plays a pivotal role in the cattle industry in both dairy and beef production systems. For instance, cattle farms rely heavily on the ability of a newborn 0739-7240/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.domaniend.2008.07.002