Reproductive

This study examined the onset of puberty, follicular dynam-ics, reproductive hormone profiles, and ability to maintain preg-nancy in cloned heifers produced by somatic cell nuclear trans-fer. Four adult somatic cell-cloned heifers, derived from a 13-yr-old Holstein cow, were compared to 4 individual age- and weight-matched heifers produced by artificial insemination (AI). From 7 to 9 mo of age, jugular venous blood samples were col-lected twice weekly, and from 10 to 11 or 12 mo of age, blood sampling was carried out every other day. After the heifers reached puberty (defined as the first of 3 consecutive blood samples with peripheral plasma progesterone concentrations of.1 ng/ml), ultrasound examination of ovaries and jugular plas-ma sample collection were carried out daily for 1 estrous cycle. Cloned heifers reached puberty later than controls (mean 6 SEM, 314.7 6 9.6 vs. 272 6 4.4 days and 336.7 6 13 vs. 302.8 6 4.5 kg for clones and controls, respectively; P, 0.05). How-ever, cloned and control heifers were not different in estrous cycle length, ovulatory follicle diameter, number of follicular waves, or profiles of hormonal changes (LH, FSH, estradiol, and progesterone). Three of the 4 clones and all 4 control heifers became pregnant after AI. These results demonstrate that clones from an aged adult have normal reproductive development. developmental biology, embryo, follicular development, ovary, pregnancy, progesteron