Dietary lipid and gross energy affect protein utilization in the rare minnow Gobiocypris rarus

An 8-week feeding trial was conducted to detect the optimal dietary protein and energy, as well as the ef fects of protein to energy ratio on growth, for the rare minnow( Gobiocypris rarus), which are critical to nutrition standardization for model fi sh. Twenty-four diets were formulated to contain three gross energy(10, 12.5, 15 kJ/g), four protein(20%, 25%, 30%, 35%), and two lipid levels(3%, 6%). The results showed that optimal dietary E/P was 41.7–50 kJ/g for maximum growth in juvenile rare minnows at 6% dietary crude lipid. At 3% dietary lipid, specifi c growth rate(SGR) increased markedly when E/P decreased from 62.5 kJ/g to 35.7 kJ/g and gross energy was 12.5 kJ/g, and from 75 kJ/g to 42.9 kJ/g when gross energy was 15.0 kJ/g. The optimal gross energy was estimated at 12.5 kJ /g and excess energy decreased food intake and growth. Dietary lipid exhibited an apparent protein-sparing eff ect. Optimal protein decreased from 35% to 25%–30% with an increase in dietary lipid from 3% to 6% without adversely ef fecting growth. Dietary lipid level af fects the optimal dietary E/P ratio. In conclusion, recommended dietary protein and energy for rare minnow are 20%–35% and 10–12.5 k J/g, respectively.

Surrogate production of genome-edited sperm from a different subfamily by spermatogonial stem cell transplantation

The surrogate reproduction technique,such as inter-specific spermatogonial stem cells(SSCs)transplantation(SSCT),provides a powerful tool for production of gametes derived from endangered species or those with desirable traits.However,generation of genome-edited gametes from a different species or production of gametes from a phylogenetically distant species such as from a different subfamily,by SSCT,has not succeeded.Here,using two small cyprinid fishes from different subfamilies,Chinese rare minnow(gobiocypris rarus,for brief:Gr)and zebrafish(danio rerio),we successfully obtained Gr-derived genome-edited sperm in zebrafish by an optimized SSCT procedure.The transplanted Gr SSCs supported the host gonadal development and underwent normal spermatogenesis,resulting in a reconstructed fertile testis containing Gr spermatids and zebrafish testicular somatic cells.Interestingly,the surrogate spermatozoa resembled those of host zebrafish but not donor Gr in morphology and swimming behavior.When pou5f3 and chd knockout Gr SSCs were transplanted,Gr-derived genome-edited sperm was successfully produced in zebrafish.This is the first report demonstrating surrogate production of gametes from a different subfamily by SSCT,and surrogate production of genome-edited gametes from another species as well.This method is feasible to be applied to future breeding of commercial fish and livestock.