Leukograms of healthy Holstein calves within the irst month of life1

Benesi F.J., Teixeira C.M.C., Leal M.L.R., Lisboa J.A.N., Mirandola R.M.S., Shecaira C.L. & Gomes V. 2012. Leukograms of healthy Holstein calves within the irst month of life. Pesquisa Veterinária Brasileira 32(4):352-356. Departamento de Clínica Médica, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Av. Professor Doutor Orlando Marques de Paiva 87, Cidade Universitária, São Paulo, SP 05508-270, Brazil. Email: [email protected] To establish reference values and to assess the in luence of age on the leukograms of healthy Holstein calves, blood samples were obtained from 300 animals. These samples were distributed equally (n=20) among 15 experimental groups according to age: birth to 8 hours, 9 to 16 hours, 17 to 24 hours, 2 days, 3 days, 4 days, 5 days, 6 to 7 days, 8 to 9 days, 10 to 11 days, 12 to 13 days, 14 to 15 days, 16 to 20 days, 21 to 25 days and 26 to 30 days of age. The maximum numbers of leukocytes (9,305.0/mL), segmented neutrophils (6,551.2/ mL) and total neutrophils (6,678.3/mL) were noted within the irst 8 hours of life, while band neutrophils peaked in number (133.3/mL) between 9 and 16 hours after birth. Meanwhile, the maximum total lymphocyte (4,992.1/μL) and typical lymphocyte (4,686.1/ μL) counts occurred between 21 and 25 days, whereas atypical lymphocytes (388.5/μL) reached their maximum number between 26 and 30 days, demonstrating an inversion of the neutrophil:lymphocyte ratio over time. Thus, the in luence of age on the leukocyte count of the evaluated calves was veri ied. The release of endogenous corticosteroids during labor or at birth may contribute to this variation in leukograms with age.