Plasma IGF-I concentrations in Holstein-Frisian heifers from birth to puberty.

none6The role of the IGF system is of particular importance in prenatal as well in postnatal growth and development. IGF-I is associated with increased somatic growth. The onset of puberty involves a complex interaction of pituitary, gonadal hormones and growth factors, such as IGF-I. The aim of the study was to study IGF-I plasma concentrations in Holstein-Friesian heifers from birth to puberty. The study was conducted on 6 female Holstein-Friesian (HF) heifers, born mature and viable. Blood samples were collected from the jugular vein into heparinized tubes, at 10 and 30 minutes (min), 3, 6, 12, 24 and 36 hours (h) after birth, at 7, 14, 21 and 28 days (d), every two weeks from 45 d to 105 d, and then monthly until after the occurrence of puberty, defined as the detection of a corpus luteum by rectal palpation. Separated plasma was stored until analyis by RIA for IGF-I. Possible IGF-I changes among each sampling time of study were statistically analysed by one way ANOVA, followed by the post Hoc Tukey test. The 6 heifer showed a normal post natal growth and development, and did not show diseases along the time of study. Because puberty occurred at different age among the 6 heifers (8-13 months of age), IGF-I plasma concentrations (means ± SD) profile from birth to puberty was subdivided in two separate figures, one reporting the profile of IGF-I levels from birth to 28 days of age (Figure 1), and another reporting IGF-I plasma levels from puberty back to 45 days of age (Figure 2). Results obtained in this study evidenced a significant (p<0.05) increase of IGF-I concentrations from birth to the time- frame between 10 min and the first 6 hours of age, probably due to the colostrums intake. Even if the colostral IGF-I are not absorbed by the intestinal mucosa, the elevated glucose status in colostrum-fed calves enhance the IGF-I hepatic synthesis resulting thus in elevated plasma IGF-I concentrations after colostrums intake [1]. From 7 to 28 days of age IGF-I return to values even lower to that recorded at birth, followed by a trend of increase from 45 days of age and with a significant (p