37 NORMALITY OF NEONATAL REFLEX IN CLONED DOGS

Abstract

Since the birth of the world’s first cloned dog, Snuppy, somatic cell nuclear transfer (SCNT) has been a useful tool to propagate the dogs with identical genetic information. However, it is known that cloned animals sometimes exhibit phenotypic instability or abnormality. There have been few investigations about the normality of the neonatal reflex in cloned animals. Therefore, the objective of this study was to evaluate the neonatal reflex in 3 breeds of cloned dogs including shepherd, retriever, and beagle from birth to 28 days of age. Through SCNT, 8 cloned dogs were produced. After birth, 3 types of neonatal reflexes were examined and scored. For examining the flexor dominance reflex, neonatal cloned dogs were held upright and the flexor position of the limb was scored. To evaluate the withdrawal and crossed extensor reflexes, neonates were placed in lateral recumbence and their forelimbs were allowed to relax. Then, the distal forelimbs were pinched and responses were scored according to the frequency and intensity (strong = score 2, variable = score 1, and absent = score 0). The standard responses of neonates were referred from Lindsay et al. (2000 Handbook of Applied Dog Behavior and Training 1, 31–47). Descriptive analysis was used, which was based on the scores from 3 referees who evaluated the videos. The flexor dominance reflex could not be observed (score 0.0) in shepherd by Day 8, in beagle by Day 14 and in retriever by Day 16. Withdrawal reflex began to decrease on Day 22 with score 1.8 for beagle and retriever but decreased in shepherd starting on Day 24 with score 1.8. Crossed extensor reflex for shepherd started to disappear on Day 14 with score 1.5 and completely disappeared (score 0.0) on Day 22; for beagle started to disappear on Day 16 with score 1.8 and was still found until Day 28 with score 1.1; for retriever started to disappear on Day 20 and 28 with score 1.7 and 0.7, respectively. Flexor dominance reflex disappeared in cloned shepherd at a similar time to standard but beagle and retriever seem delayed 6 to 8 days compared with the reference. Withdrawal reflex in all breeds showed normal changes that should persist until adulthood. Cross extensor reflex in shepherd was close to reference but in beagle and retriever was delayed beyond Day 28; this reflex should disappear before adulthood. This study demonstrated that normal neonatal reflexes were identified in the cloned dogs, with some variations among breed. To adapt neonatal reflex as a marker to confirm phenotypic normality in cloned dogs, further investigation using various breeds of cloned dogs and greater numbers of subjects is needed.

This study was supported by IPET (#316002-05-1-SB010), RDA (#PJ010928032016), Research Institute for Veterinary Science, Natural Balance Korea and the BK21 plus program.