Abstract
Balanced chromosomal rearrangements, mainly reciprocal translocations, are considered to be the causative agent of several clinical conditions in farmed pigs, resulting in hypoprolificacy and economic losses. Literature suggests that reciprocal translocations are heritable and can occur de novo. The prevalence rate of these balanced structural rearrangements of chromosomes differs from country to country and varies between 0.5% and 3.3%. The Australian pig population is descendent of a small founder population and has since been a closed genetic group since the 1980s. Hence, any incident of reciprocal translocation along with the pedigree of boars that contribute sperm for artificial insemination has the potential to have an economic consequence. To date, there has been no published account for screening of reciprocal translocation associated with hypoprolificacy in the Australian pig population. In this study, we performed standard and molecular cytogenetic analyses to identify evidence of chromosome rearrangements and their association with hypoprolificacy in a representative 94 boar samples from a commercial nucleus herd. We identified three novel rearrangements between chromosomes 5 and 14, between chromosomes 9 and 10, and between chromosomes 10 and 12. In addition, we also detected a reciprocal translocation between chromosomes 3 and 16 that has previously been detected in pig herds in France. The prevalence rate was 6.38% within the samples used in this study. All four rearrangements were found to have an association with hypoprolificacy. Further study and routine monitoring will be necessary to identify any further rearrangements that will allow breeders to prevent the propagation of reciprocal translocations from generation to generation within the Australian pig population.
Highlights
Chromosomal abnormalities, mostly balanced structural rearrangements, are known to be the source of several clinical conditions in livestock, such as congenital malfunction [1,2]
Our analysis identified three novel balanced chromosomal rearrangements, while two of them were translocation between chromosome 5 and 14 and chromosome 12 and 10, and two reciprocal translocations Cells 2021, 10, x FOR PEER RbEeVtIEwWeen chromosome 9 and 10 and chromosomes 3 and 16 (Figure 1e). 4 of 11
Our karyotype analysis revealed a balanced translocation of the q-arm of chromosome 5 to the p-arm of chromosome 14 in three boars (Table 1)
Summary
Chromosomal abnormalities, mostly balanced structural rearrangements, are known to be the source of several clinical conditions in livestock, such as congenital malfunction [1,2]. Reciprocal translocations (RTs) relate to the balanced chromosomal rearrangement or exchange of uneven chromosomal fragments leading to the development of genetically ‘unbalanced’ sperm. Such rearrangements result in hypoprolificacy in farmed boars. Any undetected fertility issues in these boars are likely to reduce litter production within breeding populations. To avoid unwanted fertility issues, semen that is used in artificial insemination (AI) is routinely checked for usual quality assessment such as sperm concentration, morphology, and motility. These assessments do not detect small-scale chromosome rearrangements, such as RTs
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