Impact of merging commercial breeding lines on the genetic diversity of Landrace pigs

Ina Hulsegge,Mario Calus,Rita Hoving-Bolink,Hendrik-Jan Megens,Kor Oldenbroek,Marcos Lopes

doi:10.1186/s12711-019-0502-6

Ina Hulsegge, Mario Calus + Show 4 more

Open Access

https://doi.org/10.1186/s12711-019-0502-6

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Abstract

BackgroundThe pig breeding industry has undergone a large number of mergers in the past decades. Various commercial lines were merged or discontinued, which is expected to reduce the genetic diversity of the pig species. The objective of the current study was to investigate the genetic diversity of different former Dutch Landrace breeding lines and quantify their relationship with the current Dutch Landrace breed that originated from these lines.ResultsPrincipal component analysis clearly divided the former Landrace lines into two main clusters, which are represented by Norwegian/Finnish Landrace lines and Dutch Landrace lines. Structure analysis revealed that each of the lines that are present in the Dutch Gene bank has a unique genetic identity. The current Dutch Landrace breed shows a high level of admixture and is closely related to the six former lines. The Dumeco N-line, which is conserved in the Dutch Gene bank, is poorly represented in the current Dutch Landrace. All seven lines (the six former and the current line) contribute almost equally to the genetic diversity of the Dutch Landrace breed. As expected, the current Dutch Landrace breed comprises only a small proportion of unique genetic diversity that was not present in the other lines. The genetic diversity level, as measured by Eding’s core set method, was equal to 0.89 for the current Dutch Landrace breed, whereas total genetic diversity across the seven lines, measured by the same method, was equal to 0.99.ConclusionsThe current Dutch Landrace breed shows a high level of admixture and is closely related to the six former Dutch Landrace lines. Merging of commercial Landrace lines has reduced the genetic diversity of the Landrace population in the Netherlands, although a large proportion of the original variation is maintained. Thus, our recommendation is to conserve breeding lines in a gene bank before they are merged.

Highlights

The pig breeding industry has undergone a large number of mergers in the past decades
The principal component analysis (PCA) clearly indicates a division of the seven Landrace lines into two main clusters; on the one hand, the former Norwegian/Finnish Landrace lines (CNF, DN and FL lines), which were introduced in the Netherlands between 1970 and 1980, and, on the other hand, the former Dutch Landrace lines (DL, FZ and SB) (Fig. 2a)
The current commercial Dutch Landrace line (TN) is a mixture of the former breeding lines, since the old breeding lines included the extremes of the first principal component (PC1)

Summary

Introduction

The pig breeding industry has undergone a large number of mergers in the past decades. Various com‐ mercial lines were merged or discontinued, which is expected to reduce the genetic diversity of the pig species. In the mid-twentieth century, a large number of breeding associations that operated regionally were responsible for pig breeding. Each of these breeding associations and breeding companies had their own breeding stock, which was usually based on the same limited number of commercial. The commercial breeding industry has seen considerable business consolidation through mergers and take-overs, which have resulted in a limited number of remaining internationally operating breeding companies [2]. Breeding lines that lost the competition in terms of performance and genetic gain were often discontinued but perhaps more often, breeding lines were merged ‘asymmetrically’, keeping the old breeding line’s name, but with extraneous influences

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