65 ASSESSMENT OF LIVE OFFSPRING SIRED BY A SOMATIC CELL NUCLEAR TRANSFER BULL, STARBUCK II

Abstract

It appears that overt phenotypic abnormalities observed in some domestic animal clones are not transmitted to their progeny, suggesting that epigenetic and genetic alterations are reset in the germline of clones. Still, little is known about the normalcy and performance of the offspring from cloned animals. The current study monitored Holstein heifers sired by a cloned bull, Starbuck II, from weaning to puberty. Genomic stability was assessed by telomere length status and chromosomal assessments. Growth parameters, blood profiles and physical exams were performed and the results were compared to those for a group of control heifers with matched breed and ages born from normal cows located in the Ponsonby Research Station (Guelph, Ontario, Canada). Once circulating progesterone concentrations were determined to be >1 ng/mL, the heifers were monitored by ultrasound to investigate follicular dynamics. Statistical analysis was performed using descriptive statistics, paired t-test, and a Tukey-Kramer post-hoc test for multiple comparisons. Compared to controls during the observation period, progeny sired by the cloned bull did not show any significant (P > 0.05) difference as in weight (mean ± SEM) (231.5 ± 29.4 vs. 237.6 ± 31.0 kg), length (160.6 ± 13.0 vs. 172.4 ± 2.7 cm), height (105.3 ± 3.72 vs. 95.5 ± 11.0 cm) and temperature (39.06 ± 0.01 vs. 39.16 ± 0.0°C). However, the cases displayed a relaxed behavior and were easier to handle than controls. This was reflected by significant differences in heart rates (83.3 ± 3.3 vs. 101.3 ± 2.6 bpm) (P = 0.005) and respiratory rates (35.4 ± 2.7 vs. 46.7 ± 3.3 rpm) (P = 0.04) for progeny and controls, respectively. Blood profiles were within normal ranges for both groups. External and internal genitalia were normal at palpation and ultrasound exam. Both groups began puberty at the expected age (10-12 months) and weight (318 to 365 kg). Follicular dynamics and progesterone concentrations corresponded to normal adult cows and were similar between groups after puberty. Telomere lengths of spermatozoa and blood samples from Starbuck II (22.23 kb and 14.19 kb, respectively) were not statistically different from normal telomere length profiles for non-cloned cattle. Telomere lengths of Starbuck II's progeny (22.52 ± 0.38 kb, n = 32) were no different compared to age-matched controls (22.20 ± 0.56 kb, n = 20). In addition, the progeny exhibited a normal karyotype in their peripheral blood leukocytes (83.14 ± 5.22% normal diploid cells). In summary, heifers sired by a cloned bull have normal chromosomal stability, growth, physical, hematological and reproductive parameters compared to normal heifers. Also, these heifers had a better response with lower stress to regular handling and restraining procedures.

This work was funded by OCAG, OMAF, and CRC.