Feed conversion ratio (FCR), the ratio between feed intake and body weight gain, is of major interest for improving aquaculture sustainability through reduced feed costs and environmental impacts. Demonstrating whether FCR measured in juvenile fish is an accurate predictor of their performance during the whole rearing period is critical to developing genetic improvement programs for this trait. This is especially true for estimates obtained in individually reared fish, for which this has high implications regarding the size of the necessary rearing structures. We obtained individual FCR from 30 male Nile tilapia Oreochromis niloticus from the GIFT strain individually reared in a recirculating system, from 36 to 260 g mean weight. They were fed twice a day and uneaten pellets were counted every day to determine the feed intake of each fish. Individual growth was monitored every week. Feed conversion ratio was estimated over two-week periods and over the whole rearing period (210 days). Phenotypic correlations between the two-week FCRs and global FCR estimations were mostly significant (ranged from 0.38 to 0.64). A significant phenotypic correlation between growth and FCR was also found: faster-growing fish had a better (lower) FCR. Individual breeding values for global FCR were estimated using FCR phenotypes from the present study and previously published heritabilities for FCR in Nile tilapia. Potential estimated genetic gain for global FCR was 2.2% per generation with 50% selection intensity. When selecting fish on their FCR from only a two-week period, approximately 50% of the reference genetic gain could be obtained with the same selection intensity. FCR measured during a two-week period at juvenile stage could be a moderately accurate approximation of the whole rearing period FCR, and could be used as a lower cost criterion to select for FCR in future genetic improvement programs using individual rearing of fish.

饲料转化率（FCR）是饲料摄入量与体重增加之间的比率，对于通过降低饲料成本和环境影响来改善水产养殖的可持续性具有重大意义。证明在幼鱼中测得的FCR是否能准确预测其在整个饲养期间的表现，对于制定针对该性状的遗传改良计划至关重要。对于在单独饲养的鱼中获得的估计值尤其如此，因为这对必要的饲养结构的大小有很大的影响。我们从30头尼罗罗非鱼Oreochromis niloticus获得了单独的FCRGIFT菌株在循环系统中单独饲养，平均重量为36至260 g。他们每天喂两次，每天对未食用的颗粒进行计数，以确定每条鱼的采食量。每周监测个人成长。在两周的时间内和整个饲养期间（210天）估算了饲料转化率。两周FCR与全球FCR估计之间的表型相关性最为显着（范围从0.38到0.64）。还发现生长与FCR之间存在显着的表型相关性：生长速度快的鱼FCR较好（较低）。使用本研究的FCR表型估算了全球FCR的个体育种值，并先前发表了尼罗罗非鱼中FCR的遗传力。估计全球FCR的潜在遗传增益为2。每代2％，选择强度为50％。仅在两周的时间内从FCR中选择鱼类时，在相同的选择强度下可获得大约50％的参考遗传增益。在幼年期的两周时间内测得的FCR可能是整个饲养期间FCR的中等准确近似值，并且可以用作在单个鱼的未来遗传改良计划中选择FCR的较低成本标准。