Abstract
In recent decades, a considerable number of local breeds have been replaced by high-yielding breeds for reasons of profitability. Many local breeds are now threatened by extinction and the loss of their native genetic diversity. The need to conserve breeds and their genetic diversity has a major importance due to the necessity for genetic change within and between populations. Novel approaches have to be explored and extended to maintain this genetic diversity. The aim of this study was the identification and implementation of breed-specific traits for a small, local sheep breed in northern Germany. The data comprised pedigree information, estimated breeding values (EBVs) of several conventional traits, and phenotypic information from a field experiment for two novel traits: 1) average daily gain under extensive circumstances (ADGE) and 2) ultrasonic measurements of muscle-fat ratio (UMFR). The experimental design included a dataset of 47 progeny from 14 pure-bred rams of German White-Headed Mutton (GWM). The methodical approach was divided into four parts: 1) the analysis of the breeding programme, 2) the identification of breed-specific traits, 3) the estimation and correlation of novel breeding values, and 4) the consequences of implementing these novel traits. Genetic parameters and correlations were conducted by applying linear mixed models. The estimates for the heritability (repeatability) were between 0.70 and 0.83 (0.42 and 0.46). The genetic correlation was positive (0.61) and in accordance with the phenotypic correlation (0.62). Average daily gain under intensive circumstances (ADGI) was moderately positive correlated with muscularity (0.60), as opposed to ADGE, which was moderately negative correlated with muscularity (-0.68). The EBV of ADGE was also moderately positive correlated with UMFR (0.64). Genetic response for ADGE enhanced to values of 481.09 g/day, 639.97 g/day, >700 g/day and >850 g/day for different selection intensity scenarios. Corresponding rates of inbreeding were 1.4%, 2.7%, 5.1%, and 7.9% after 10 years of selection. Genetic response for UMFR increased to 0.92, 1.34, 2.41, and >2.75, whereas remaining rates of inbreeding increased to 1.1%, 2.2%, 5.1%, and 7.9%. ADGI and ADGE were tendentially negatively correlated (-0.11), which strengthen the assumption of a biased ADGI. ADGE has a positive influence on meat-quality aspects (UMFR). Optimal use of reference sires with predefined selection intensity achieves genetic response for ADGE and UMFR with simultaneously acceptable rates of inbreeding.
Highlights
The domestication of livestock species has created an enormous variety of breeds due to a long history of migrations, selection, and adaptation [1]
average daily gain under intensive circumstances (ADGI) and average daily gain under extensive circumstances (ADGE) were tendentially negatively correlated (−0.11), which strengthen the assumption of a biased ADGI
The unbiased trait of ADGE was positively correlated with the meat-quality trait of UMFR (0.64), which is in accordance with the investigated positive regression and correlation of 0.62 between collected phenotypes for both traits (Figure 3)
Summary
The domestication of livestock species has created an enormous variety of breeds due to a long history of migrations, selection, and adaptation [1]. Selection programmes have become more efficient and have accelerated the genetic gain in a small number of breeds. These high-yielding breeds have replaced many local breeds, which has resulted in a high rate of loss of local breeds due to extinction [3]. Different approaches and considerations were discussed by Meuwissen [3] for the purpose of breed conservation These methods consisted of aspects of optimum contribution selection [8] [9], integrating life and cryoconservation schemes [10] [11], rotational breeding schemes [12], and the introduction of novel traits from conserved populations into commercial breeding populations [13] [14]. Most local breeds are implemented into conventional breeding programmes, where the specific traits
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