Abstract
The following results could be obtained from the present study on the relationship between the variations in the number of vertebrae and the heritability of variations in the number of the vertebrae of Landrace pigs by means of the analysis of the data with 117 sires, 425 dams, and 3819 piglets from them.
1. The number of thoracic vertebrae of Landrace pigs ranged from 14 up to 17. The frequency of emergence of the type with 16 vertebrae was the highest, while the counterpart of the type with 15 vertebrae was about half of that of 16. The frequencies of the types of 14 and 17 vertebrae were very low.
2. The number of lumbar vertebrae ranged from 5 up to 7. Those with 6 lumbar vertebrae was of the highest frequency, followed by those with 7 and 5 lumbar vertebae in the decresing order.
3.The number of vertebrae including both the thoracic and lumbar vertebrae ranged from 20 up to 23. Those with 21 and 22 vertebrae shared approx. 95%, and were of the highest frequency.
4. Even with the mating of parents with the same numbers of vertebrae, variations in the numbers of vertebrae were noted in the piglets farrowed by them. Mating of the pigs with larger numbers of vertebrae produced piglets with larger average numbers of vertebrae than the counterparts of the piglets farrowed by the parents with smaller numbers of vertebrae. The numbers of vertebrae showed no differences by generation.
5. The heritability of the numbers of vertebrae was as described in Tables 6, 7, and 8. The results suggested that selection of individual pigs for mating would be effective for increasing the numbers of vertebrae because of the high heritability, except for the one concerning lumbar vertebrae.
