Cysteine supplementation pre-freeze and post-thaw improves integrity and reduces oxidative stress in cryopreserved ram spermatozoa.

Cryopreserved ram sperm is highly sensitive to oxidative stress by reactive oxygen species (ROS) which impair sperm function and integrity. Antioxidants such as cysteine can mitigate the effect of ROS, although the optimal concentration or timing of supplementation is unknown. This study aimed to determine the effect of concentration and timing of cysteine supplementation on the integrity and function of cryopreserved ram spermatozoa. Nine ejaculates were collected from three Texel rams then cryopreserved and supplemented with cysteine (0, 0.5, or 1.0 mg/mL) added pre-freeze (PF), post-thaw (PT) or pre-freeze and post-thaw (PF + PT) generating seven treatments: 1) control 0 mg/mL, 2) PF 0.5 mg/mL, 3) PF 1 mg/mL, 4) PT 0.5 mg/mL, 5), PT 1.0 mg/mL, 6) PF + PT 0.5 mg/mL and 7) PF + PT 1.0 mg/mL. Sperm motility, viability, acrosome integrity, ROS production and penetrability through artificial cervical mucus were assessed post-thaw. Cysteine supplementation reduced ROS production which thereby improved spermatozoa motility, viability, acrosome integrity and penetrability (p < 0.001) Sperm integrity for all parameters was greatest in spermatozoa treated PF + PT with 1.0 mg/mL cysteine, although treatment pre-freeze or post-thaw also improved integrity beyond the control. This study has identified that 1.0 mg/mL cysteine is most beneficial and has highlighted the importance of preventing oxidative stress in spermatozoa post-thaw. These finding can help to mitigate the detrimental effect of cryopreservation on spermatozoa and aid the development of cryopreservation protocols in sheep.

The effect of dietary n-3/n-6 polyunsaturated fatty acid ratio on salmonid alphavirus subtype 1 (SAV-1) replication in tissues of experimentally infected rainbow trout (Oncorhynchus mykiss).

Salmon pancreas disease (SPD) is one of the most commercially significant viral diseases of farmed Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) in Europe. In this study, the potential for dietary mitigation of the disease using different polyunsaturated fatty acid (PUFA) profiles was assessed in rainbow trout. We experimentally infected fish with salmonid alphavirus subtype 1 (SAV-1), the causative agent of SPD. These fish were fed two diets with different n-3/n-6 PUFA ratio (high omega 3, 3.08, and high omega 6, 0.87). We assessed the influence of the diets on the fatty acid composition of the heart at 0 days post infection (d.p.i.) (after 4 weeks of feeding the experimental diets prior to SAV-1 infection), and sampled infected and control fish at 5, 15 and 30d.p.i. Viral E1 and E2 glycoprotein genes were quantified by two absolute real-time PCRs in all the organs sampled, and significantly lower levels of the virus were evident in the organs of fish fed with high omega 6. Characteristic pathological lesions were identified in infected fish as early as 5d.p.i., with no significant differences in the pathology lesion scores between the two dietary regimes. This study shows that decreasing the n-3/n-6 PUFA ratio in experimental diets of rainbow trout changes the fatty acid content of the fish, and is associated with reduced SAV-1 replication in rainbow trout.