A longitudinal study on growth and growth variables in dogs of four large breeds raised in domestic environments

The main objective of this study was to describe the growth patterns of 4 large dog breeds Newfoundland (NF), Labrador retriever (LR), Leonberger (LEO), and Irish wolfhound (IW)] raised in domestic environments and concomitant changes in 2 growth-related clinical variables: total serum alkaline phosphatase (ALP) and the circumference of the distal radius and ulna (CDRU). The second objective was to investigate whether these measurements were affected by a range of independent variables like age, sex, litter number, and birth weight. Seven hundred dogs were included in the study, and BW data, separated by breed and sex, were fitted to the Gompertz function. Birth weight, adjusted for litter number, differed significantly between sexes for 3 breeds (LEO, P = 0.004; NF, P = 0.02; LR, P = 0.009) and approached significance for IW (P = 0.07). Estimated mean BW increased rapidly during the first 100 d after birth in all 4 breeds, then plateaued, with maturity being reached between 351 (female LR) and 413 d (male NF). Estimated mature BW ranged from 30.8 kg for the female LR up to 65.7 kg for the male IW. Weight gain, as expressed by the derivative of the Gompertz function, reached its peak in the smallest breed (LR) at the youngest age, 89 d for the females and 95 d for males. Log-transformed BW was significantly related to age, breed, and sex, and the age x sex and age x breed interactions. Within breeds, age, birth weight, and litter number had a significant effect on log-transformed BW. The estimated average CDRU increased from 90 d of age toward a peak at 180 d. Thereafter, CDRU declined and stabilized at about 1 yr of age. The estimated total ALP concentrations decreased from 90 to 360 d of age, after which they stabilized, at mean concentrations varying among breeds from 98 to 131 IU/L. Maximum least squares mean total ALP concentrations were found at 3 mo of age in all breeds, with the greatest least squares mean concentration in the IW breed (713 IU/L). In a mixed model analysis of the complete data set, total ALP was affected (P < 0.001) by age, breed, and the interaction of age x breed. This study described the main factors influencing growth and provided reference data for other studies, including those related to nutrition and disorders of growth.