There are still concerns over sperm quality when plant-based diluents are used instead of animal-based semen extenders. Therefore, in our study we compared the effects of one soybean lecithin-based (AndroMed^®) and two egg yolk-based (BullXcell^® and Optidyl^®) commercially available extenders on post-thaw in vitro sperm quality. Fifty ejaculates collected from ten bulls were aliquoted into three parts and diluted with the above-mentioned extenders. Post-thaw sperm viability, mitochondrial membrane potential (MMP), plasma membrane integrity, and acrosome status were analysed immediately after thawing (0 h) and at an hourly interval during 2-h incubation at 38 °C. Sperm functionality variables were assessed by simultaneous quadruple staining using flow cytometry. Semen stored in Optidyl^®had a greater viability, plasma membrane and acrosome integrity than that stored in AndroMed^® and BullXcell^® (P < 0.05). With the use of BullXcell^® there was a higher percentage of sperm with high MMP (P < 0.05) when compared with the other extenders. The incubation affected the development of sperm quality parameters differently as the variables related to the plasma membrane showed an increase, while MMP and acrosome integrity showed a decline. Although the semen from all bulls responded to treatments in a similar manner, significant intra- and inter-male differences were found. In conclusion, the results clearly displayed the beneficial effects of egg yolk over soybean lecithin supplementation on in vitro sperm quality.

This work aimed to evaluate the quantity and the quality of flushed embryos based on the metabolic status of dairy cows, lactation number, and size of the ovaries. Fifty-nine Holstein cows on 1^st to 5^th lactation were enrolled in the experiment. Monitoring took place during the period from October to November and from March to June. Cows with corpus luteum were included for the hormonal treatment – superovulation and timed insemination. The cow was inseminated, resp. re-inseminated, during the induced heat with insemination doses from one bull from the same batch. Embryo flushing was performed on the 7^th day after the first insemination. We isolated individual embryos after flushing, and morphologically evaluated them under a stereo microscope. The metabolic status of tested cows was determined based on the ratio between fat and protein in milk around the period of embryo flushing (< 1.1; 1.1–1.3; > 1.3). Data about fat and protein content were taken from milking parlour records. Data were evaluated in SAS v9.4 with GLM procedure. The results of our study showed that there is a significant relationship between the fat/protein ratio and the total number of flushed embryos, resp. the number of transferable embryos. The highest number of flushed and transferable embryos were collected from the group of cows with fat/protein ratio between 1.1–1.3. The fat/protein ratio within these values represents cows in an optimal metabolic state. We also observed a significant positive relationship between the size of the ovaries and the number of flushed and transferable embryos. Lactation number did not significantly affect monitored parameters. The assessment of the fat/protein ratio might become a useful tool for the evaluation of cows selected for embryo transfer. Our findings could be used to improve the efficacy of the superovulation system, with the aim to extract the maximum number of transferable embryos.

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Sperm cryopreservation is a complex process consisting of several steps, the details of which are not yet universally agreed upon. The objective of this study was to evaluate the effects of different equilibration times and freezing rates on post-thaw resilience and functional integrity. Collected semen from five Holstein bulls (30 samples in total) were split into 4 aliquots to produce frozen straws after 2 different equilibration times (2 h and 4 h) and freezing rates (2-phase and 3-phase). After thawing, the sperm characteristics were measured by flow cytometry. A linear model procedure was used to determine the effects of bull, equilibration time, freezing rate and interaction between them, on sperm variables. The evaluated sperm characteristics included spermatozoa with intact plasma and acrosomal membrane (PMAI), PMAI with high mitochondrial membrane potential (HMMP), spermatozoa with plasma membrane damage (PMD), and spermatozoa with acrosome damage (AD) were analysed immediately, 1 h and 2 h after thawing. In conclusion, the extension of the equilibration time from to 4 h in combination with 2-phase freezing rate led to a significant improvement in all measured parameters of frozen-thawed spermatozoa (P < 0.01).

The aim of this study was to evaluate the effects of 3 different commercially available extenders – AndroMed® (soy lecithin-based), Optidyl® (with the addition of ionized egg yolk), and BULLXcell® (with the addition of fresh egg yolk) – on bull spermatozoa quality, which was evaluated using the parameters of spermatozoa motility, viability, plasma membrane damage, acrosome damage, and mitochondrial activity after thawing and during a 2 h long thermoresistance test. The spermatozoa quality indicators were appraised by computer-assisted semen analysis and a flow cytometer. Significant differences (P < 0.01) between bulls were registered in all indicators measured. The highest average values of spermatozoa total motility and viability were achieved using BULLXcell® extender (44.33%; 52.06%). Variances in comparing this extender with Optidyl® and AndroMed® were −0.83%, −2.64%; −8.33%, −9.51%. The differences found between the egg yolk-based diluents (BULLXcell® and Optidyl®) and AndroMed® were significant (P < 0.01). Therefore, the more valuable extenders for bull semen dilution were egg yolk-based extenders, which provided higher post-thaw spermatozoa survival and quality than the soy lecithin-based extender.