Perinatal concentrations of 17β-estradiol and testosterone in the toe claws of female and male dogs from birth until 60 days of age.

This study was conducted to assess concentrations of 17β-estradiol (E2) and testosterone (T) in toe claws of puppies collected at birth, at 30 and at 60 days of age, evaluating changes relating to age and effect of puppy sex, Apgar score, bodyweight at birth, "litter effect", litter size, and maternal age. Puppies (n = 89), 46 males and 43 females, with normal weight and without malformations, were assigned for the study. Within 12 h of birth tips of toe claws were clipped, and the re-growth tissue of the claws was collected at 30 and 60 days of age. Steroid quantifications occurred using a radioimmunoassay. The results indicated there were lesser concentrations (P < 0.001) of both hormones at 30 and 60 days of age than at birth and that concentrations were similar at 30-60 days of age. There were greater (P < 0.001) T concentrations in males than females, with there being an interaction between sex and sampling time (P < 0.01). The Apgar score was positively (P < 0.001) related to T concentrations in toe claws at birth. The bodyweight was positively correlated (P < 0.05) with T concentrations, with an interaction among puppy sex, bodyweight and sampling time (P < 0.05). Results of the present study confirmed the usefulness of toe claws as a matrix for study of hormonal changes in perinatology of dogs. Results of the study also indicate there are greater E2 and T concentrations at birth compared with 30 and 60 days of age that could be the result of these prenatal steroids affecting fetal development.