Evaluation of connectedness between herds for three pig breeds in China

Abstract

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.

Case Study on Increasing Breeding Value Estimation Reliability of Reproductive Traits in Serbian Highly Prolific Large White and Landrace Sows

“…The presence of some degree of connectedness between herds is a basic requirement for estimating the breeding value with satisfactory accuracy and reliably comparing animals between herds [ 14 , 18 ]. The absence of genetic links between herds can have a negative impact on EBV bias.…”

“…The absence of genetic links between herds can have a negative impact on EBV bias. To highlight the importance of the degree of connectedness, many researchers have investigated the influence of genetic association on EBV [ 14 , 15 , 16 , 17 , 18 , 19 , 34 ]. However, there is little research indicating the importance of connectedness between herds when estimating breeding values of litter size traits in sows with low heritability.…”

“…If herds are insufficiently connected the comparison of breeding values between animals from different herds may be biased. Therefore, measuring the across-herd connectedness is important in order to achieve a more reliable genetic evaluation among pig herds (between a large number of farms/herds) [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

The genetic connectedness calculated from genomic information and its effect on the accuracy of genomic prediction

“…It is well recognized that genetic connectedness among China pig herds was generally established through using of common sires ( i . e ., sires with progeny in multiple herds or sires born in one herd with progeny in another herd) or through transferring of seedstock from one herd to another[ 3 ]. Therefore, to mimick the genetic connectedness created by common sires, 400 founder females of Herd3 were all from the first generation of Herd2, while the 20 founder males of Herd3 came from Herd1 and Herd2.…”

“…Traditionally, genetic connectedness can be calculated through pedigree-based method [ 1 – 4 ]. However, the pedigree information used in China cannot guarantee its integrity and accuracy, which in turn may lead to lower or unreasonable estimates of genetic connectedness across pig nucleus farms in China[ 3 , 5 , 6 ]. The lack of extensive and reliable pedigree information is a general problem in developing countries[ 7 ], particularly in China, where the source of the pigs are extremely complex (e.g., introduced pigs from Denmark, the United States, Canada and France).…”