Spermatozoa motility and viability
The effects of different temperatures (36, 38, 40, 42 and 44°C) on the motility and viability rates in canary semen are given in Table 1. The effect of different temperature values on the motility and viability rate in canary semen was very significant (P<0.001). The highest motility value (62%) was found in the Trial-3 group (at 40°C). The sperm viability rate was the highest in the Experiment-2 (at 38°C) groups. In addition, according to the polynomial analysis, linear (P<0.001) and quadratic (P<0.001) effects were very significant.
In our study, the viability rate was higher at 38°C. In our study, the difference between 38 and 40°C motility values was statistically insignificant. Although 38°C (56%) and 40°C (62%) were statistically close to each other in terms of motility, it was seen that 40°C gave more positive results numerically. The average body temperature of the canary is 41.6°C (
Brain and Prozesky, 1963). When the results of our study were examined, it was seen that temperatures below body temperature were more positive. However, temperatures below a specific temperature negatively affected spermatozoa’s viability and motility values. Our study observed a rapid decrease in motility and viability at 42°C after 40°C. After 40°C, viability and sperm motility decreased due to increasing temperature values. It was also observed that sperm motility remained stable for a shorter period above 38°C. Significant was found: a sharp decrease in motility and viability at 42°C and 44°C. The viability of poultry sperm can be preserved for a long time in the female reproductive tract at body temperature. However, it is known that sperm viability is negatively affected in the external environment at the same temperature. However, poultry semen can be preserved longer at low temperatures in the external environment (
Sarkar, 2020;
Sasanami et al., 2013). It is thought that slowing down the metabolic rate at low temperatures in the external environment prolongs the survival time of spermatozoa (
Sarkar, 2020). Spermatogenesis in birds occurs a few degrees below body temperature.
(Beaupre et al., 1997). According to the results of our study, temperatures below body temperature were more optimistic regarding spermatological parameters in canaries. However, it is interesting that the difference between the body temperature expressed for canaries and the temperature values determined as a result of the study is not high and is at close values. Studies on songbirds have emphasized that temperatures of 37-38°C are ideal
(Dogliero et al., 2015). When the results obtained from the studies are evaluated, it is seen that they overlap with our study.
Spermatozoa speed
The effect of different temperature values on spermatozoa velocity in canary semen is given in Table 2. When the spermatozoa swimming speeds of the experimental groups were examined, it was observed that most of the five specimens (60%) in the Trial-1 group moved ‘slowly.’ In Trial-3, Trial-4 and Trial-5, it was determined that most of the five samples (60%, 80% and 60%, respectively, according to the trial groups) were ‘fast.’ In one group (Trial-2), a large majority (80%) of the five samples was determined to have a ‘moderate’ speed.
When sperm speeds were evaluated, it was seen that the average speed of 38°C was more stable. Notably, as the temperature increased to 42°C, the movement speed also increased. However, the viability rate decreased due to increasing temperature values after 40°C. It was also observed that sperm motility could not be maintained for a long time above 38°C. Contrary to general usage, he emphasized the need to use different temperature values according to the animal species to minimize the effect of the semen from the external environment. In a study on sperm speed and morphology, a temperature of 35°C was preferred. However, depending on the animal species, 37-39°C was used
(Lupold et al., 2009). A study conducted on budgies stated that the mobility value at 41°C was higher than at 38°C
(Madeddu et al., 2022). A study reported that spermatozoa speed increases when appropriate temperature values are exceeded
(Yang et al., 2019). As a result, although there was an increase in spermatozoa speed when the optimum temperature was increased to a certain degree, a decrease in viability and motility rates was observed. Studies conducted on songbirds appear to support our study.
Sperm motility values and viability rates vary in poultry species (
Sarkar, 2020). In the study, the effects of temperature values on bird semen were examined and it was observed that the viability of semen kept outside at body temperature decreased quickly. Generally speaking, sperm motility decreases at both low and high levels. It is also known that sperm viability is higher at lower temperatures up to specific temperature values (
Sarkar, 2020). When the results of our study were evaluated, it was observed that the highest survival rate was at 38°C. Although the viability rates were similar at 36°C and 40°C, it was observed that 38°C and 40°C were close to each other in terms of motility. The motility value is lower at 36°C than at 38°C. However, after 40°C, the decrease in motility and vitality values increased and the maximum decrease was observed at 44°C. Therefore, our study supports the view expressed in the study that sperm motility decreases at both high and low temperatures. In this regard, it can be said that a temperature of 38°C was successful for Gloster canary semen. As a result, it was observed that when the optimum temperature was increased to a certain degree, although there was an increase in spermatozoa speed, there was a decrease in viability and motility rates. It seems that studies conducted on songbirds support our study.
It has been reported that the motility and viability values of fresh semen in turkeys are over 70% (
Kuzlu and Taskın, 2017). In the study, fresh semen was collected with a 1 mL plastic syringe and diluted with physiological saline at a ratio of 1:2. In addition, the density value for turkey semen was found to be 3.5-5×10
9 sp/mL. In our study, fresh semen was collected from a canary. 2 µL of semen was examined by diluting it with DMEM diluent at a ratio of 1:2. It is seen that the density value and semen volume of the semen diluted at equal dilution rates are significantly lower than turkey semen. Considering this situation, it is thought that canary semen is more sensitive to external temperature changes. In our study, using equal time intervals as much as possible in the evaluation of each canary semen and having the same person make the evaluation minimizes individual errors between samples and shows that the appropriate temperature under equal conditions is 38°C.