Department of Aquaculture, Faculty of Fisheries, Kasetsart University, Bangkok, Chatuchak, Thailand.
Department of Animal Science, Faculty of Agriculture, Kasetsart University, Bangkok, Chatuchak, Thailand.
J Fish Dis. 2019 Nov;42(11):1553-1562. doi: 10.1111/jfd.13074. Epub 2019 Aug 26.
The potential of selection to improve resistance to streptococcosis was evaluated in a commercial population of Nile tilapia in Thailand. The base generation (G0) consisted of offspring from 98 sires and 149 dams using a partly nested design. At 60 days post-hatch, 30 fish from each family were injected intraperitoneally with a Streptococcosis agalactiae solution (1 × 10 CFU/ml) and evaluated for 14 days. Disease resistance was recorded as the number of days from challenge until death (DD) and as a binary (BIN) trait (dead/alive) on day 14. Three models were used for genetic analyses: Cox frailty model for DD; animal model for DD; and animal model for BIN. Age at challenge was fitted as a covariate and contemporary group as fixed or random effect, depending on the model. Fish from the 18 most resistant families were selected to produce the first generation (G1). Heritability estimates for G0 were 0.22, 0.14 ± 0.02 and 0.11 ± 0.02 for the Cox, linear DD and linear BIN models, respectively. Selection response indicated that the risk of death decreased to 54%, survival time increased to 3.4 days and survival rate increased to 21%. These results suggest that genetic improvement is possible for this population.
在泰国的一个尼罗罗非鱼商业群体中评估了选择对链球菌病抗性的改良潜力。基础群体（G0）由 98 个父本和 149 个母本的后代组成，采用部分嵌套设计。在孵化后 60 天，每个家系的 30 条鱼通过腹腔注射链球菌病溶液（1×10 CFU/ml）进行注射，并在 14 天内进行评估。抗病性记录为从攻毒到死亡的天数（DD）和第 14 天的二进制（BIN）性状（死亡/存活）。使用了 3 种模型进行遗传分析：用于 DD 的 Cox 脆弱性模型；用于 DD 的动物模型；以及用于 BIN 的动物模型。攻毒时的年龄被拟合为协变量，根据模型的不同，当代群体被拟合为固定或随机效应。从 18 个最具抗性的家系中选择鱼来产生第一代（G1）。对于 Cox、线性 DD 和线性 BIN 模型，G0 的遗传力估计值分别为 0.22、0.14±0.02 和 0.11±0.02。选择反应表明，死亡风险降低了 54%，存活时间增加了 3.4 天，存活率增加了 21%。这些结果表明，该群体的遗传改良是可能的。
