ORIGINAL RESEARCH Age-related changes in biochemical and hematologic variables in Borzoi and Beagle puppies from birth to 8 weeks Emilie Rosset 1 , Benoit Rannou 2 , Gre ´ gory Casseleux 1 , Karine Chalvet-Monfray 3 , Samuel Buff 1 1 Centre d’E ´ tude et de Recherche en Reproduction et en E ´ levage Canin (CERREC; Center for Study and Research in Carnivore Reproduction and Breeding); 2 Biochemistry and Endocrinology Unit; and 3 UR 346 Animal Epidemiology INRA, Universite ´ de Lyon – VetAgro Sup – Campus Ve ´ te ´ rinaire de Lyon, Marcy l’E ´ toile, France Key Words Dog, neonate, reference interval, robust method Correspondence Emilie Rosset, Universite ´ de Lyon – VetAgro Sup – Campus Ve ´ te ´ rinaire de Lyon, 1 Avenue Bourgelat, 69280 Marcy l’E ´ toile, France E-mail: emilie.rosset@vetagro-sup.fr DOI:10.1111/j.1939-165X.2012.00415.x Background: Nonspecific signs of illness and availability of only limited information about expected biochemical and hematologic values in puppies make formulation of a differential diagnosis challenging for veterinarians. Objectives: The objectives of this prospective study were to describe age- related changes in biochemical and hematologic variables in Borzoi and Beagle puppies from birth to 8 weeks and to compare results with adult ref- erence intervals (RIs). Methods: Biochemical and hematologic analytes in blood collected in hep- arin and EDTA from 31 clinically healthy puppies (21 Beagle and 10 Borzoi dogs) were measured or calculated each week from birth to 8 weeks of age. RIs were calculated using the parametric robust method after Box–Cox transformation. Results: There were no significant differences between values of puppies and adults for ALT activity, glucose concentration, MCHC, WBC count, and platelet count. Total protein concentration, RBC count, and HCT were lower and creatine kinase activity was higher in puppies of all ages com- pared with these variables in adults. Compared with adult RI, in puppies urea concentration was higher at birth and week 1, creatinine concentra- tion was lower at weeks 1–5, ALP activity was higher at all weeks except for weeks 4 and 6, hemoglobin concentration was lower at weeks 1–8, MCV was higher at birth and week 1, and reticulocyte count was higher at all weeks except week 1. Statistically, mixed models accounted for evaluation of the same puppies each week and in most cases demonstrated an effect of age and sometimes breed. Some reference intervals should be used with caution owing to potential outliers. The 90% confidence intervals exceeded those recommended by the International Federation of Clinical Chemistry. Conclusions: Clinicians should be aware of temporal changes in biochemi- cal and hematologic values for puppies during the first 2 months of life to avoid misinterpretation of results. Introduction Despite improvements in veterinary care over the last 30 years, mortality in puppies from birth to weaning age (8 weeks) has not decreased, with reported rates ranging from 12% to 30%. 1,2 Neonatal illness and death of newborn puppies may represent major eco- nomic losses for breeders and a diagnostic challenge for the practitioner. Clinical signs of illness in neonates are often nonspecific and include dehydration and hypothermia. 3,4 The volume of blood that can be col- lected from newborns is limited by their small size and immaturity, which increases their susceptibility to hypovolemic shock, 5 but diagnosis based only on physical examination is problematic 6–8 In addition, there are few published reference intervals (RI) for puppies. The most recent report of biochemical profiles of newborn puppies was published in 1995, 2,9 and a Vet Clin Pathol 41/2 (2012) 272–282 ©2012 American Society for Veterinary Clinical Pathology 272 Veterinary Clinical Pathology ISSN 0275-6382