Evaluation of zearalenone andα‐zearalenol toxicity on boar sperm DNA integrity

Abstract Background Sperm DNA integrity is considered essential for successful transmission of the paternal genome, fertilization and normal embryo development. DNA fragmentation index (DFI, %) has become a key parameter in the swine artificial insemination industry to assess sperm DNA integrity. Recently, in some elite Norwegian Landrace boars (boars with excellent field fertility records), a higher level of sperm DFI has been observed. In order to obtain a better understanding of this, and to study the complexity of sperm DNA integrity, liquid preserved semen samples from elite boars with contrasting DFI levels were examined for protamine deficiency, thiol profile and disulphide bonds. Additionally, the DNA methylation profiles of the samples were determined by reduced representation bisulphite sequencing (RRBS). Results In this study, different traits related to sperm DNA integrity were investigated (n = 18 ejaculates). Upon liquid storage, the levels of total thiols and disulphide bonds decreased significantly, while the DFI and protamine deficiency level increased significantly. The RRBS results revealed similar global patterns of low methylation from semen samples with different levels of DFI (low, medium and high). Differential methylation analyses indicated that the number of differentially methylated cytosines (DMCs) increased in the low-high compared to the low-medium and the medium-high DFI groups. Annotating the DMCs with gene and CpG features revealed clear differences between DFI groups. In addition, the number of annotated transcription starting sites (TSS) and associated pathways in the low-high comparison was greater than the other two groups. Pathway analysis showed that genes (based on the closest TSS to DMCs) corresponding to low-high DFI comparison were associated with important processes such as membrane function, metabolic cascade and antioxidant defence system. Conclusion To our knowledge, this is the first study evaluating DNA methylation in boar sperm cells with different levels of DFI. The present study shows that sperm cells with varying levels of DNA fragmentation exhibit similar global methylation, but different site-specific DNA methylation signatures. Moreover, with increasing DNA fragmentation in spermatozoa, there is an increase in the number of potentially affected downstream genes and their respective regulatory pathways.

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141 Antioxidant Supplementation Alleviates DNA Damage in Boar Sperm Induced by Tropical Heat Stress

Reproduction Fertility and Development ◽

10.1071/rdv30n1ab141 ◽

2018 ◽

Vol 30 (1) ◽

pp. 210 ◽

Cited By ~ 1

Author(s):

S. T. Peña ◽

B. Gummow ◽

A. J. Parker ◽

D. B. B. P. Paris

Keyword(s):

Dna Damage ◽

Heat Stress ◽

Dna Integrity ◽

Antioxidant Supplementation ◽

Sperm Dna Damage ◽

Progressive Motility ◽

Sperm Dna Integrity ◽

Sperm Dna ◽

Boar Sperm ◽

The Tropics

Seasonal heat stress is known to significantly diminish reproductive performance in pigs, particularly in the tropics, costing the industry millions in annual losses. The boar’s reduced capacity to sweat and non-pendulous scrotum, combined with the widespread use of European breeds in the tropics, makes this species particularly vulnerable to heat stress. Although heat stress is traditionally considered a sow problem, recent mouse studies demonstrate that heat stress-induced sperm DNA damage can result in arrested development and loss of early embryos. Our study investigated the impact of tropical summer heat stress on the quality and DNA integrity of boar sperm, and trialled antioxidant supplementation to alleviate the problem. Data, expressed as mean ± SEM, were analysed by one-way repeated-measures ANOVA with pairwise Bonferroni tests. Motility of sperm obtained from Large White boars (n = 5) housed in the dry tropics of Townsville, North Queensland, Australia, was characterised by computer-assisted sperm analysis but did not differ between summer, winter, or spring (total motility: 71.3 ± 8.1 v. 90.2 ± 4.2 v. 70.8 ± 5.5%, respectively; P > 0.05; progressive motility: 35.4 ± 7.0 v. 46.6 ± 4.0 v. 41.7 ± 2.8%, respectively; P > 0.05). Sperm DNA integrity in 20,000 sperm/boar per season, evaluated using TUNEL and flow cytometry, revealed 16-fold more DNA-damaged sperm in summer than winter, and nearly 9-fold more than spring (16.1 ± 4.8 v. 1.0 ± 0.2 v. 1.9 ± 0.5%, respectively; P ≤ 0.05). However, boar feed supplemented with 100 g/boar per day of proprietary custom-made antioxidants during summer significantly reduced sperm DNA damage to 9.9 ± 4.5% and 7.2 ± 1.6% (P ≤ 0.05) after 42 and 84 days of treatment respectively. Total and progressive motility were not altered by the supplement. In summary, sperm DNA integrity is compromised in boars during summer, suggesting that boar factors may contribute to seasonal embryo loss in sows. Moreover, such damage appears undetectable using traditional measures of sperm motility. Antioxidant supplementation during summer appears to mitigate the negative impact of heat stress on sperm DNA integrity.

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