Marie-Etancelin Christel, Vitezica Zulma G, Bonnal Laurent, Fernandez Xavier, Bastianelli Denis
UMR1388 Génétique, Physiologie et Systèmes d'Elevage, INRA, F-31326 Castanet-Tolosan, France.
Genet Sel Evol. 2014 Jun 10;46(1):38. doi: 10.1186/1297-9686-46-38.
"Foie gras" is produced predominantly in France and about 90% of the commercialized product is obtained from male mule ducks. The melting rate (percentage of fat released during cooking) is the main criterion used to determine the quality of "foie gras". However, up to now the melting rate could not be predicted without causing liver damage, which means that selection programs could not use this criterion.
Fatty liver phenotypes were obtained for a population of over 1400 overfed male mule ducks. The phenotypes were based on two types of near-infrared spectra (on the liver surface and on ground liver) in order to predict the melting rate and liver composition (ash, dry matter, lipid and protein contents). Genetic parameters were computed in multiple traits with a "sire-dam" model and using a Gibbs sampling approach.
The estimates for the genetic parameters show that the measured melting rate and the predicted melting rate obtained with two near-infrared spectrometer devices are genetically the same trait: genetic correlations are very high (ranging from +0.89 to +0.97 depending on the mule duck parental line and the spectrometer) and heritabilities are comparable. The predictions based on the spectra of ground liver samples using a laboratory spectrometer correlate with those based on the surface spectra using a portable spectrometer (from +0.83 to +0.95 for dry matter, lipid and protein content) and are particularly high for the melting rate (higher than +0.95). Although less accurate than the predictions obtained using the spectra of ground liver samples, the phenotypic prediction of the melting rate based on surface spectra is sufficiently accurate to be used by "foie gras" processors.
Near-infrared spectrometry is an efficient tool to select liver quality in breeding programs because animals can be ranked according to their liver melting rate without damaging their livers. Thus, these original results will help breeders to select ducks based on the liver melting rate, a crucial criterion that defines the quality of the liver and for which there was previously no accurate predictor.
“肥鹅肝”主要产于法国，约90%的商业化产品取自雄性骡鸭。融化率（烹饪过程中释放的脂肪百分比）是用于判定“肥鹅肝”品质的主要标准。然而，到目前为止，在不造成肝脏损伤的情况下无法预测融化率，这意味着选育计划无法采用该标准。
获取了1400多只过度喂养的雄性骡鸭群体的脂肪肝表型。这些表型基于两种近红外光谱（肝脏表面和肝脏研磨物），以预测融化率和肝脏成分（灰分、干物质、脂质和蛋白质含量）。使用“父系-母系”模型并采用吉布斯抽样方法计算多性状的遗传参数。
遗传参数估计表明，用两种近红外光谱仪测得的融化率和预测的融化率在遗传上是同一性状：遗传相关性非常高（根据骡鸭亲本系和光谱仪不同，范围从+0.89到+0.97），且遗传力相当。使用实验室光谱仪基于肝脏研磨物样本光谱的预测与使用便携式光谱仪基于表面光谱的预测相关（干物质、脂质和蛋白质含量的相关系数从+0.83到+0.95），对于融化率尤其高（高于+0.95）。虽然基于表面光谱的融化率表型预测不如基于肝脏研磨物样本光谱的预测准确，但对于“肥鹅肝”加工商来说已足够准确可用。
近红外光谱法是育种计划中选择肝脏品质的有效工具，因为可以根据动物肝脏的融化率对其进行排名而不损害其肝脏。因此，这些原始结果将有助于育种者根据肝脏融化率选择鸭子，这是定义肝脏品质的关键标准，而此前尚无准确的预测指标。
