Cryopreservation of farm animal gametes and embryos:recent updates and progress

Cryopreservation has undergone tremendous advances and is widely used in animal production based on decades of study of cellular permeability, freezability and empirical generalization. Several improvement are particularly important: the cryopreservation protocol has been continuously re?ned over the years to achieve greater reproductive performance; cryoprotective agents are more effective and less toxic than previously; there has been signi?cant innovation in advanced cryopreservation systems and carriers. Despite this, there are still problems that urgently require practical solutions, such as remedies for cryodamage and encouraging the use of frozen–thawed porcine sperm in pig production.

Expression analysis for candidate genes associated with eggshell mechanical property

Damaged eggshells result in losses of eggs.The genetic mechanism of variable eggshell strength is still unclear.The current study was conducted to verify whether the eggshell calcification related genes,CALB1,SPP1,DMP4,BMP2 and SLIT2,were associated with eggshell mechanical property.For this purpose quantitative PCR（q-PCR） analysis was performed to detect gene expression between two groups of hens laying strong and weak eggs.The hens were selected from 360 White Leghorn layers at 60 wk to ensure that the strong and weak eggs differed significantly in breaking strength but not in eggshell thickness and weight.Using this special strong/weak eggshell model,we found that the expression of CALB1 in the uterus of strong shell group was about 3-fold higher（P〈0.05） than that in weak shell group.The DMP4 expression was significantly higher（2-fold,P〈0.05） in the uterus of weak shell group than that in strong shell group.However,no difference was observed for genes of SPP1,SLIT2 and BMP2 between these two groups.The current study provides a new insight to investigate the association of candidate genes with eggshell mechanical property.

Statistical considerations for genomic selection

Genomic selection is becoming increasingly important in animal and plant breeding, and is attracting greater attention for human disease risk prediction. This review covers the most commonly used statistical methods and some extensions of them, i.e., ridge regression and genomic best linear unbiased prediction, Bayesian alphabet, and least absolute shrinkage and selection operator.Then it discusses the measurement of the performance of genomic selection and factors affecting the prediction of performance. Among the measurements of prediction performance, the most important and commonly used measurement is prediction accuracy. In simulation studies where true breeding values are available, accuracy of genomic estimated breeding value can be calculated directly. In real or industrial data studies, either trainingtesting approach or k-fold cross-validation is commonly employed to validate methods. Factors influencing the accuracy of genomic selection include linkage disequilibrium between markers and quantitative trait loci, genetic architecture of the trait, and size and composition of the training population. Genomic selection has been implemented in the breeding programs of dairy cattle, beef cattle, pigs and poultry. Genomic selection in other species has also been intensively researched, and is likely to be implemented in the near future.