Evaluation of connectedness between herds for three pig breeds in China.

Using data on age at 100 kg of three pig breeds (Large White, Landrace and Duroc) the connectedness between herds in China was evaluated by the connectedness rating (CR) method. The results show that most herds in China have low average CR (0-3.59%) with other herds. In Large White, of the 36 herds analyzed there are 20 herds, which are connected with at least one other herd. In Landrace and Duroc, of the 27 and 18 herds analyzed, only four and five herds, respectively, were found having connectedness with other herds. Generally, the connectedness exists only among two or few herds in the same region. A certain degree of connectedness between herds is a precondition for cross-herd genetic evaluation. A national or regional cross-herd genetic evaluation is not practicable at the present time in China. More intense efforts are needed to establish and enhance the connectedness between herds by means of extensively using artificial insemination (AI) in the swine industry in China.