Dipartimento di Scienze e Tecnologie Veterinarie per la Sicurezza Alimentare, Facolta `di Medicina Veterinaria, Universita `di Milano, Milano, Italy Reference Intervals and Age-related Changes for Platelet Count, Mean Platelet Volume and Plateletcrit in Healthy Pre-weaning Piglets in Italy M. Faustini 1,3 , V. Bronzo 2 , G. Maffeo 1 , V. Russo 1 , E. Munari 1 and D. Vigo 1 Addresses of authors: 1 Dipartimento di Scienze e Tecnologie Veterinarie per la Sicurezza Alimentare, Facolta `di Medicina Veterinaria, Laboratorio di Fisiologia; 2 Dipartimento di Patologia Animale, Igiene e Sanita `Pubblica Veterinaria, Sezione di Malattie Infettive, Facolta `di Medicina Veterinaria, Universita `degli Studi di Milano, Via G. Celoria, 10, 20133 Milano, Italy; 3 Corresponding author: Tel.: +39 0250317938; Fax: +39 0250317941; E-mail: massimo.faustini@unimi.it With 1 figure and 3 tables Received for publication: February 10, 2003 Summary Platelet count (PLT) mean plateletvolume (MPV) and plateletcrit (PCT) were determined for 117 Landrace · Large White pigletsaged 3–21 days; countswere performed with an automated blood cell counter (ABX Pentra 120). Refer- ence valueswere estimated following the guidelines of the International Federation ofClinical Chemistry (IFCC)and the International Committee for Standardization in Haema- tology (ICSH). The calculated central 95% reference limits for PLT was 49.9–516.2 · 10 9 /l, for MPV 6.71–9.91 fl and for PCT 0.009–0.395%. When observations are divided into three age groups (about 1 week each) there is an increase in mean PLT count and PCT in 2-week piglets, and a decrease in MPV from the first to the third week oflife. These ref- erence values provide guidelines for interpreting for experi- mentaland clinicalobservations, as well as for monitoring of the health status of similar aged piglets determined using automated impedance-light focusing methodology. Introduction The assessment of the haematological status in normal pigs is important for monitoring the health and welfare, but also to provide some basic physiological informations, because adult pigs and more frequentlypigletsare used as modelsin experimental physiology. With recently developed automated blood analysers using impedance and light scatter counters, many additional haematological variables, especially relating to platelets, can be determined. The primary platelet-related variables include platelet count, plateletcrit and mean platelet volume.There are very few reports documenting reference intervalsfor platelet-related parameters, let alone platelet count,where current technology is used and which include a description of analytical and statistical methods, especially for piglets during the first month of life. The perceived biological importance of platelet-related variables relevance is growing continuously: mean platelet volume (MPV) is associated with platelets activation, as demonstrated in horses (Weiss et al., 1998) and in various pathophysiological conditions in humans (Giles, 1981; Bessman et al., 1985; Karnad and Poskitt, 1985). Recently, Kapsoritakis et al. (2001) reported the usefulness of MPV as a marker of platelet activity in inflammatory bowel disease in humans. Jaremo et al.(2000)observed that pre- eclampsia in women is related to elevate mean platelet volume as well as disturbances in platelet density. The aim of this study was to establish reference limits for plateletcount,mean platelet volume and plateletcrit in pre- weaning piglets, and to assess possible age-related changes in order to improve understanding and interpretation of these variables in newborn piglets, during the routinary monitoring of wellness and health status. Materials and Methods Sample Collection and Haematological Analysis The study was conducted on 120 Landrace · Large White pre- weaning piglets, randomly selected from 30 litters in two modern pig farms located in northern Italy. The proportion of males (n ¼ 64) and females (n ¼ 56) was similar. All subjects were healthy, housed with their dams in pens with concrete floor and exposed to natural September–October photoperiod. Piglets health status was evaluated by anamnesis (environment and previous pathologies) and general examination (skeletal devel- opment, nutritional state, behaviour and reactivity to manipu- lation,muscular tonicity, skin and mucosal appearance, and lymph nodes).All pigletswere treated with iron–dextran (200 mg iron by intramuscular route in the neck region) the second day oflife. Caudectomy and male castration were performed within 72h of life; blood samples were collected before all treatments. The age of subjects was between 2and 21 days(mean age: 10.88 ± 7.89 days; weaning:21stday). Blood samples were collected during the morning hours (8.00– 10.00 a.m.)by the same trained person in the September– October period. Blood was collected from the external jugular vein (Framstad et al., 2000) using a 5-ml polypropylene dispo- sable syringe with a 22-gauge needle. Blood specimens were transferred immediately into 2-ml K3 EDTA vacuum tubes (Vacutainer; Becton-Dickinson, Le Pont de Claix, France), stored at 15C and forwarded to the laboratory within 3 h from bleeding. All analyses were performed the same day of collection. Blood samples were analysed for platelet count (PLT), mean platelet volume (MPV) and plateletcrit (PCT) by means of an automated combined impedance-light focusing haematology counter(ABX Pentra 120; ABX Italia, Rome, Italy). The instrumentwas maintainedand calibratedfollowing the manufacturer’s guidelines. Calibration of Pentra 120 was U.S. Copyright Clearance Center Code Statement: 0931–184X/2003/5009–0466 $15.00/0 www.blackwell-synergy.com J. Vet. Med. A 50, 466–469 (2003) 2003 Blackwell Verlag, Berlin ISSN 0931–184X