Reaction time as a libido indicator and its relation to pre-freeze and post-thaw sperm quality in bulls.

Libido and sperm quality output relationship is already not clear in farm animals. The present study compared reaction time (RT) as a libido indicator and the pre-freeze and post-thaw sperm quality of AI bulls. Before the collection of ejaculates (n = 53, from 22 AI bulls [4.2 ± 1 years of age]), RTs were collected using a chronometer as the interval between the bull's arrival at the semen collection area and his first false mount (FM) on another male. The ejaculates were examined for their volume, concentration and motility. Subsequently, all aliquots were diluted with a commercial semen extender and equilibrated for 3 h before freezing. Frozen semen samples were thawed and examined for sperm kinematics using CASA, plasma membrane and acrosome integrity of sperm (PMAI) by flow cytometry. Additionally, the temperature humidity index (THI) values were assessed during the study. Multiple linear regression analysis was used to analyse the data. The results indicated that THI had a significant effect on libido (p < .001). However, libido had no effect on either pre- or post-thaw sperm quality parameters except for the velocity of the average pathway (VAP) (p < .05). Therefore, relying solely on RT -libido- as an indicator of bull sperm quality at AI stations may not be reliable, as it is a complex behavioural assessment.

Fertility comparison of frozen bull semen stored in cryogenic deep freezer (-152 °C) and LN2 container.

The present study aimed to use cryogenic deep freezers that could be a feasible alternative for cryopreserved semen storage. A total of 284 straws from three Simmental bulls and 272 Simmental cows were used. The experimental group consisted of 151 semen straws that were stored at -152 °C for a week. Moreover, the control group consisted of 133 semen straws that were stored at -196 °C. Firstly, two samples per bull (n = 6) were examined in terms of sperm kinetic parameters by CASA. Furthermore, plasma membrane, acrosome integrity (PMAI) and high mitochondrial membrane potential (HMMP) were analyzed by flow cytometry. Then, artificial inseminations were performed on Simmental cows with 272 straws belonging to two groups. Then, 56th-day Non-return Rate (NRR56) was determined. All spermatological data were subjected to a linear mixed model. Chi-Square test was performed to NRR56 between storage temperature groups. Also, logistic regression analysis was used to examine the effect of bull, storage temperature and age of cows on pregnancy status. While age of cows was included in the final logistic regression model, effect of bull x storage temperature was not included because it was found as non-significant. The post-thaw PMOT and STR of cryopreserved bull semen, which was stored at -152 °C, had lower and statistically significant values (p < 0.05). However, frozen bull semen, which were stored at -152 °C, kept its fertility ability as which stored at -196 °C. Besides, NRR56 of semen stored at -152 °C and -196 °C were detected as 57.24% (83/145) and 55.91% (71/127), respectively (p > 0.05). Nevertheless, these results should be supplemented with more pre-freezing and post-thaw sperm quality analyses and more fertility data for increasing the accuracy of the method.

Gallic and carnosic acids improve quality of frozen-thawed ram spermatozoa.

The objective was to determine effects of gallic acid (GA) and carnosic acid (CA), present in carob pods and rosemary extract respectively, on frozen-thawed ram spermatozoa. Thirty ejaculates were collected from five Merino rams, pooled, diluted in Tris-based extender and divided into five equal portions containing: 0.05 or 2 mM of GA; 0.05 or 0.2 mM of CA; or no additive (control). Extended semen was equilibrated at +4°C, loaded into straws, held 5 cm above liquid nitrogen for 12 min then plunged. Computer-aided sperm analysis was used to assess motility, whereas flow cytometry was used to assess high mitochondrial membrane potential (HMMP) and percentages of spermatozoa with plasma membrane and acrosome integrity (PMAI). Spermatozoa supplemented with 2 mM GA had greater total motility than control spermatozoa (39.9 ± 3.01 vs. 29.2 ± 1.31%, mean ± SEM, p < .05). The PMAI was greatest in 0.2 mM CA (13.3 ± 0.68%), whereas HMMP was highest in 0.05 mM CA but lowest in control (22.9 ± 4.95 and 11.4 ± 3.64% respectively; p < .05). In conclusion, for cryopreservation of ram semen in Tris-based extender, supplementation with 2 mM GA increased post-thaw motility, whereas supplementation with 0.05 mM CA enhanced mitochondrial function.