Influence of post‐thawing thermal environment on bovine sperm characteristics and in vitro fertility

Abstract

Our aim was to evaluate the effects of three thermal environments over time on kinetics, functionality and in vitro fertility of cryopreserved bovine spermatozoa. Four ejaculates from five bulls (n = 20) were cryopreserved. After thawing, semen was evaluated (0 hr), incubated for 4 hr in T36.0 (36.0°C), T38.0 (38.0°C) and T39.5 (39.5°C), and analysed every hour (1 hr, 2 hr, 3 hr, 4 hr). In vitro production of embryos was performed at 0 hr and 4 hr. Sperm motility and cell kinetics (Computer‐Assisted Sperm Analysis) were impaired after 2 hr at T38.0 and T39.5 (p < 0.05). Flow cytometry revealed an increase in the cells with injured plasma membrane to 39.5°C and a general reduction in the mitochondrial potential over time (p < 0.05). In vitro fertility was impaired in all temperatures after 4 hr, but there was no difference between 36.0°C and 38.0°C. Our results suggest that the ex situ resilience of semen at 36.0°C after thawing with no major damage to the quality is limited to 3 hr. In normothermia or in thermal stress, sperm cells present a gradual reduction of movement and functionality, which were more significant after 1 hr of incubation. The in vitro production of embryos is impaired when the semen is kept in a thermal environment ≥36.0°C for 4 hr.

Changes in the Cellular Distribution of Tyrosine Phosphorylation and Its Relationship with the Acrosomal Exocytosis and Plasma Membrane Integrity during In Vitro Capacitation of Frozen/Thawed Bull Spermatozoa

“…In addition, total motility and PMI during the incubation period significantly decreased to similar values as previously reported in Canchim bull within the same incubation time [43]. Intracellular ROS generation associated with sperm capacitation has been pointed to as a major agent…”

“Effect of the addition of different catalase concentrations to a TRIS-egg yolk extender on quality and in vitro fertilization rate of frozen-thawed bull sperm’’

“…However, to explain this astonishing result it should be emphasized that compared to sperm cryopreserved without catalase the addition of this antioxidant did not improve DNA integrity before 12 h after thawing of frozen sperm. In vitro oocytes are fertilized by bovine sperm within the first 4 h after thawing [19]. At this time point sperm frozen without and with catalase showed the same percentage of DNA intact sperm in our study.…”

Response to stress in biological disorders: Implications of stress granule assembly and function

“…Therefore, exogenous and endogenous forms of insults (eg high temperature) affect mammalian spermatogenesis and ultimately lead to subfertility and even infertility. 105 Offspring from male mice with a heat‐treated scrotum mated with normal female mice, and exhibited lower weight than those from males without heat treatment. 106 Studies have shown that oxidative stress is a leading outcome of heat damage in spermatogenic cells, 1 , 107 while sperms and oocytes are the most sensitive to heat, 108 , 109 , 110 and the somatic supporting cells such as Sertoli cell in the testis are also affected.…”

“…In most mammals, the testicles are located in the scrotum outside the body cavity, where spermatogenesis usually occurs. Therefore, exogenous and endogenous forms of insults (eg high temperature) affect mammalian spermatogenesis and ultimately lead to subfertility and even infertility 105 . Offspring from male mice with a heat‐treated scrotum mated with normal female mice, and exhibited lower weight than those from males without heat treatment 106 .…”