An essential component in the development of sustainable pig production is the reduction of nitrogen excretion in fattening pigs. Pig feeds typically contain high levels of dietary crude protein, and due to incomplete conversion to muscle tissue, excess nitrogen is excreted, resulting in environmental problems such as nitrate pollution and greenhouse gas emissions. Therefore, improving protein efficiency (PE), i.e., the proportion of dietary protein that remains in the carcass, is desirable. The aim of this study was to estimate the heritability (h2) of PE and its genetic correlations with phosphorus efficiency, three performance, seven meat quality and two carcass quality traits when pigs were fed a 20% protein-restricted diet, using 1071 Swiss Large White pigs. To determine PE, the intake of feed with known nutrient content was accurately recorded for each pig and the nitrogen and phosphorus content of the carcass was determined using dual-energy X-ray absorptiometry. We found an average PE of 0.39 ± 0.04 and a heritability of 0.54 ± 0.10. PE showed a high genetic correlation with phosphorus efficiency (0.61 ± 0.16), moderate genetic correlations with feed conversion ratio (− 0.55 ± 0.14) and average daily feed intake (− 0.53 ± 0.14), and a low genetic correlation with average daily gain (− 0.19 ± 0.19). While PE has favourable genetic correlations with the performance traits and some meat quality traits, there is a potentially unfavourable correlation of PE with meat colour (redness [rg = − 0.27 ± 0.17]; yellowness [rg = − 0.31 ± 0.18]) and intra-muscular fat (IMF; rg = − 0.39 ± 0.15). Feed conversion ratio (FCR) also showed unfavourable genetic correlations with meat lightness, redness yellowness, IMF and cooking loss. PE is a heritable trait that can be considered in breeding programs to reduce the environmental impact of pig production. We found no strong negative correlation of PE with meat quality traits, and that there is potential to indirectly select for improved phosphorus efficiency. Selecting nutrient efficiencies might be a more suitable strategy to reduce nitrogen pollution from manure than focusing on FCR because the latter also shows genetic antagonism with some meat quality traits in our population.

中文翻译：

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蛋白质效率的遗传分析及其与蛋白质限制饮食下生产性能和肉质性状的关联

发展可持续养猪生产的一个重要组成部分是减少育肥猪的氮排泄。猪饲料通常含有高水平的膳食粗蛋白，由于未完全转化为肌肉组织，多余的氮被排出体外，导致硝酸盐污染和温室气体排放等环境问题。因此，需要提高蛋白质效率（PE），即保留在胴体中的日粮蛋白质的比例。本研究的目的是评估 PE 的遗传力 (h2) 及其与磷效率、三种性能、七种肉质和两种胴体质量性状的遗传相关性，当猪饲喂 20% 蛋白质限制日粮时，使用 1071 Swiss Large白猪。要确定 PE，准确记录每头猪的已知营养含量饲料的摄入量，并使用双能X射线吸收法测定胴体的氮和磷含量。我们发现平均 PE 为 0.39 ± 0.04，遗传力为 0.54 ± 0.10。PE 与磷效率 (0.61 ± 0.16) 具有高度遗传相关性，与饲料转化率 (- 0.55 ± 0.14) 和平均日采食量 (- 0.53 ± 0.14) 具有中等遗传相关性，与平均日增重具有低遗传相关性 ( − 0.19 ± 0.19)。虽然 PE 与生产性能特征和一些肉质性状具有良好的遗传相关性，但 PE 与肉色（红色 [rg = − 0.27 ± 0.17]；黄色 [rg = − 0.31 ± 0.18]）和内部可能存在不利的相关性- 肌肉脂肪 (IMF; rg = − 0.39 ± 0.15)。饲料转化率 (FCR) 也显示出与肉的亮度、红度、黄度、IMF 和蒸煮损失的不利遗传相关性。PE 是一种可遗传性状，可以在育种计划中加以考虑，以减少生猪生产对环境的影响。我们发现 PE 与肉质性状没有很强的负相关性，并且有可能间接选择以提高磷效率。选择营养效率可能是比关注 FCR 更合适的减少粪便氮污染的策略，因为后者也显示出与我们人群中某些肉质性状的遗传拮抗作用。PE 是一种可遗传性状，可以在育种计划中加以考虑，以减少生猪生产对环境的影响。我们发现 PE 与肉质性状没有很强的负相关性，并且有可能间接选择以提高磷效率。选择营养效率可能是比关注 FCR 更合适的减少粪便氮污染的策略，因为后者也显示出与我们人群中某些肉质性状的遗传拮抗作用。PE 是一种可遗传性状，可以在育种计划中加以考虑，以减少生猪生产对环境的影响。我们发现 PE 与肉质性状没有很强的负相关性，并且有可能间接选择以提高磷效率。选择营养效率可能是比关注 FCR 更合适的减少粪便氮污染的策略，因为后者也显示出与我们人群中某些肉质性状的遗传拮抗作用。