CALF AND DISEASE FACTORS AFFECTING GROWTH IN FEMALE HOLSTEIN CALVES IN FLORIDA, USA

A prospective cohort study was undertaken to determine calf-level fact ors that affect performance (growth) between birth and 14 months of ag e in a convenience sample of approximately 3300 female Holstein calves born in 1991 on two large Florida dairy farms. Data collected on each calf at birth included farm of origin, birth date, weight, height at the pelvis, and serum total protein (a measure of colostral immunoglob ulin absorption). Birth season was dichotomized into summer and winter using meteorological data collected by University of Florida Agricult ural Research Stations. Data collected at approximately 6 and 14 month s of age included age, weight, height at the pelvis, and height at the withers. Growth in weight and stature (height) was calculated for eac h growth period; growth period 1 (GP1) = birth to 6 months, and growth period 2 (GP2) = 6 to 14 months. Health data collected included date of initial treatment and number of treatments for the diseases diarrhe a, omphalitis, septicemia, pneumonia and keratoconjunctivitis. After a djusting for disease occurrence, passive transfer of colostral immunog lobulins had no significant effect on body weight gain or pelvic heigh t growth. Season of birth and occurrence of diarrhea, septicemia and r espiratory disease were significant variables decreasing heifer growth (height and weight) in GP1, These variables plus farm, birth weight a nd exact age when '6 month' data were collected explained 20% and 31% of the variation in body weight gain and pelvic height growth, respect ively, in GP1. The number of days treated for pneumonia before 6 month s of age significantly decreased average daily weight gain in GP2 (P < 0.025), but did not affect stature growth. Treatment for pneumonia af ter 6 months of age did not significantly affect weight or height gain after age 6 months. Neither omphalitis nor keratoconjunctivigtis expl ained variability in growth in either o fthe growth periods. (C) 1998 Elsevier Science B.V.