68 GROWTH, REPRODUCTION, AND LACTATION IN SOMATIC CELL-CLONED HOLSTEIN COWS AND THEIR PROGENY

Abstract

We investigated the safety of somatic cell-cloned Holstein cows and the analogy (growth and milk performance) of the cloned cows and their progeny. Individually, the cloned cows were produced using the same fibroblasts of a Holstein cow as the donor cells. All cows were fed in accordance with NRC (1999) standards during the experimental period. Three cloned cows (clone group), their 3 progeny (progeny group), and 3 cows produced with artificial insemination (AI, control group) were reared under general group feeding. Viability, fertility, milk yield,and blood characteristics in clone, progeny, and control groups were examined. Statistical analyses were carried out by Student's t-test. The birth weight in the clone group (55.2 ± 6.3 kg (mean ± SD)) was heavier than that of the control group (44.8 ± 5.6 kg (P > 0.05)); it was also heavier than that of an upper limit (51.0 kg) and standard value (40.0 ± 5.8 kg) of Holstein heifers in Japan. However, no significant change in the amount of dry matter intake per kg body weight/day was observed between the clone group (0.97 ± 0.06 kg) and the control group (0.9 ± 0.02 kg). As to blood characteristics in the raising phase, the number of red blood cells in the clone group (684.8 ± 16.8 × 10⁴ µL) was decreased slightly (P < 0.01) compared with that in the control group (823.3 ± 26.1 × 10⁴ µL). However, there were no differences in other blood test items between clone and control groups. Furthermore, we found that there were no differences in estrous cycles and plasma progesterone concentrations between clone and control groups. All cloned and control cows that had been inseminated became pregnant and delivered normally. During the period from 21 days before expected date of confinement to 10 days after parturition, relative to the blood characteristics, the number of blood cells in the clone group (499.9 ± 77.5 × 10⁴ µL) tended to be lower (P < 0.01), when compared to that in the control group (711.2 ± 39.9 × 10⁴ µL); no differences were observed in plasma estrogen and progesterone concentrations between clone and control groups throughout the measurement period. In the first lactation period, there were no differences in total amount of milk produced in the first 305 days of lactation, milk percentage, milk protein rate, and solids-not-fat between clone and control groups. The total amount of milk produced in the first 365 days in cloned cows was almost equal to that of the original cow who provided donor cells. In 3 progeny of the cloned cows, the average birth weight was not different from that in the control group and the standard growth value. In the raising period, there were no differences in changes of the weight and height of a body and of the dry matter intake per day, and in the blood characteristics between progeny and control groups. Conceivably, our results suggest that the cloned Holstein cows and their progeny have normal growth, reproductive, and lactation characteristics, although the birth weights of the cloned cows were larger than those of control cows.