Seasonal Variations in Red Deer (Cervus elaphus) Hematology Related to Antler Growth and Biometrics Measurements ENRIQUE GASPAR-LO ´ PEZ 1,2 , TOMA ´ S LANDETE-CASTILLEJOS 2–4 , JOSE ANTONIO ESTEVEZ 2–4 , FRANCISCO CEACERO 2,4 , LAUREANO GALLEGO 2–4 , AND ANDRE ´ S JOSE GARCI ´ A 2–4Ã 1 Venadogen S.L. Paseo de la Innovacio ´n 1, Albacete, Spain 2 Seccio ´n de Recursos Cinege ´ticos y Ganaderos, IDR, Universidad de Castilla-La Mancha, Albacete, Spain 3 Departamento de Ciencia y Tecnologı ´a Agroforestal y Gene ´tica, ETSIA, Universidad de Castilla-La Mancha, Albacete, Spain 4 Instituto de Investigacio ´n en Recursos Cinege ´ticos, IREC (CSIC, UCLM, JCCM), Campus Universitario s/n, Albacete, Spain The aim of the study was to relate seasonal hematology changes with the rest of physiological variations suffered by red deer, such as antler and biometrics cycle, and to assess the relationship between hematology and the effort performed in antler development. Blood samples were taken from 21 male red deer every 4 weeks during 18 months. Samples were analyzed for the main hematological parameters. Simultaneously, biometrics measurements were taken, such as antler length, body weight, body condition score, testicular diameter (TD), and thoracic and neck girth. All the blood cell types (erythrocytes, leukocytes, and platelets) showed seasonal variations, increasing as antler cleaning approached, as did hematocrit and hemoglobin. The final size of antlers was negatively related to leukocyte count, nonlymphoid leukocyte count, red cell distribution width, mean corpuscular hemoglobin, mean platelet volume, and TD, whereas it was positively related to body condition during antler growth. Huge seasonal variations in some hematological values have been found to be related to changes in antler and biometrics measurements. Since these variations are even greater than the caused by deer handling, they should be taken into account when evaluating hematology in deer populations. J. Exp. Zool. 315:242–249, 2011. & 2011 Wiley-Liss, Inc. How to cite this article: Gaspar-Lo ´pez E, Landete-Castillejos T, Estevez JA, Ceacero F, Gallego L, Garcı ´a AJ. 2011. Seasonal variations in red deer (Cervus elaphus) hematology related to antler growth and biometrics measurements. J. Exp. Zool. 315:242–249. Deers undergo impressive physiological changes throughout the year. One of the most evident change is the antler development, which is mainly used as a weapon in the intraspecific combat during mating season (Chapman, ’75). However, antler growth is not an isolated aspect in deer physiology, since it is accompanied by an increase in the ability to use them during mating season (Verme and Ullrey, ’84). The antler cycle begins in spring, with the cast of the old set. After casting, the new antler grows and at the end of summer it is cleaned from velvet (Suttie et al., ’91). This cycle is controlled by seasonal endocrinological changes (Suttie et al., ’91; Gaspar- Lo ´pez et al., 2010) that are triggered by the transduction of the photoperiod by the pineal gland (Garcı ´a et al., 2003). These endocrine signals have been reported to affect hematopoiesis in other species (Pages et al., ’92; Sletvold et al., ’98). Though the Published online 23 February 2011 in Wiley Online Library (wileyonline library.com). DOI: 10.1002/jez.670 Received 2 December 2010; Accepted 24 January 2011 Grant Sponsor: Ministerio de Ciencia e Innovacio ´n; Grant numbers: AGL2007- 63838/gan; PBI 05-040; PAC 06-01304298; PTQ 09-02-01923; Grant Sponsor: Junta de Comunidades de Castilla-La Mancha; Grant number: PET2006-0263. Ã Correspondence to: Andre ´s Jose Garcı ´a, Seccio ´n Recursos Cinege ´ticos y Ganaderos, Instituto de Desarrollo Regional, Campus Universitario s/n, 02071 Albacete, Spain. E-mail: andresjose.garcia@uclm.es ABSTRACT J. Exp. Zool. 315:242–249, 2011 & 2011 WILEY-LISS, INC. RESEARCH ARTICLE