Effect of Ram Age on Structural and Functional Competence of Frozen-Thawed Spermatozoa in Dairy Sheep

Abstract

The objectives of this study were to investigate the influence of ram age on structural and functional competence of frozen-thawed spermatozoa and to test the hypothesis that increasing number of sperm bound to the zona pellucida in vitro was associated with decreasing in vivo fertility of frozen semen. Rams were allocated into two groups. Each group consisted of five rams aged either 1-2 years (young) or 4-5 years (mature). Three successive ejaculates were collected from each ram using an artificial vagina. Only ejaculates of >or= 2.5 x 10(9) sperm/ml and 80% sperm progressive motility were pooled per ram, diluted with Bioxcell medium and frozen in 0.25 ml straws. The end points of post-thawing semen evaluation were computer-assisted cell motility analysis, sperm capacitation (chlortetracycline assay), simultaneous assessment of plasma membrane integrity, mitochondrial membrane potential and condensation status of nucleus, per-cell analysis of lipid peroxidation using C11-BODIPY(581/591), sperm-hemizona binding (HZB) ability and sperm fertility after laparoscopic insemination of ewes (n = 114) in the progestagen-synchronized oestrus. The results showed that mature rams had significantly lower values of sperm hyperactivated motility and peroxidized sperm, higher percentages of live non-capacitated sperm and sperm cells with intact plasma membrane, functional mitochondria and condensed chromatin, as well as, greater lambing rate and ewe prolificacy. Sperm HZB binding ability was higher (p < 0.05) for young than for mature rams. Significant correlations were found between number of spermatozoa bound to the zona pellucida and semen fertility (r = -0.63 to -0.71). In conclusion, mature rams have better semen quality and in vivo fertility than young rams. Cryocapacitation can be involved in decreasing ram semen fertility as evidenced by the high number of spermatozoa bound to the zona pellucida in vitro.

Effects of testicular hemodynamic and echogenicity changes on ram semen characteristics

“…Previous studies reported seasonal changes in ram semen quality, while our results revealed that the ultrasonographic evaluation of testicular blood flow is also correlated with major semen characteristics depending on season. Lymberopoulos, Tsakmakidis, and Khalifa () reported that Chios rams of 4–5 years old (similar age with the adult rams group of our study) had better semen quality and in vivo fertility than younger rams of 1–2 years old. Furthermore, Batissaco et al.…”

Effects of Broodstock Age and Sperm Collection Time over a Natural Spawning Period on Sperm Cryopreservation in Farmed Greenlip Abalone, Haliotis laevigata

“…In this study, most of the parameters evaluated were not significantly different between the abalone in the two age groups at respective spawning times. These results do not agree with the studies where sperm collected from older broodsotck produce a better ability to tolerate cryopreservation in comparison with their younger counterparts, such as found for rams (Lymberopoulos et al ) and white Italian ganders, Anser anser (Lukaszewicz et al ). However, caution should be taken as there was only 1 yr difference in age between the two age groups used in this study.…”

“…Therefore, if sperm collected from 2‐yr‐old rather than 3‐yr‐old abalone can be cryopreserved for selective breeding, it can lead to substantial time and cost savings and economic benefits for breeding programs. However, the age of abalone may affect the ability of sperm to tolerate cryopreservation, as such age‐dependent effects have been detected in other species, such as Chios sheep (Lymberopoulos et al ) and rooster (Long et al ). The aim of this study was to test the hypothesis that broodstock age and sperm collection time in a natural spawning period can influence the ability of sperm to tolerate cryopreservation.…”

Age-related changes in quality and fertility of porcine semen

“…However, Karabinus et al (1990) recorded a high incidence of chromatin instability and a low proportion of intact acrosomes in spermatozoa of young bulls. Furthermore, in a recent study on dairy sheep in our lab, Lymberopoulos et al (2010) observed that mature rams had signifi cantly lower values of sperm hyperactive motility and peroxidized sperm, greater percentages of sperm with intact plasma membrane, functional mitochondria and condensed chromatin, as well as greater lambing rate and ewe prolifi cacy. These results are in accordance with the results of our investigation, in which young boars demonstrated higher values of sperm morphological abnormalities, chromatin instability and sperm head length than mature boars after 24 h of semen storage.…”