BACKGROUND: The heterogeneity of ejaculate indicates that fertility is still variable among bulls and that more stringent evaluation methods are needed to identify the ejaculates suitable for AI. OBJECTIVE: To identify and characterize the sperm subpopulations (SP) in
thawed semen doses of Nelore and Angus bulls and to evaluate the influence of these sperm subpopulations on pregnancy rate in cows submitted to fixed-time AI (FTAI). MATERIALS AND METHODS: A dose of postthawed semen from each bull ( n =18; consisting of Angus n = 9 and
Nelore n = 9) was analyzed for: sperm kinetics; morphology and plasma membrane integrity; and the determination of the sperm subpopulations. Differences between the groups were estimated with the t-test considering a significance level of <5%. RESULTS: There was no influence
between breeding bulls for sperm morphology, plasma membrane integrity, and pregnancy rate ( P > 0.05). Regarding the kinetic parameters evaluated by the CASA system, Nelore had greater values, for cells with slow velocity (Angus: 16.4 %; Nelore: 21.74%; P = 0.028). In contrast,
ANGUS bulls had more static cells (Angus: 27.2%; Nelore: 9.3%; P = 0.048). Based on CASA system data and clustering procedures, four sperm subpopulations were statistically established. In Angus bulls, a higher level of fast and nonlinear spermatozoa were found in SP3 (33.3%), followed
by SP1 (32.7%) with fast and progressive spermatozoa. Whereas, SP1 of Nelore bulls had 33.8% fast and progressive spermatozoa, followed by 32.2% of SP3 with fast and nonlinear spermatozoa. CONCLUSION: Both breeds of bulls presented similar proportions of sperm SP. Consequently, no influence
on the pregnancy rates was shown in cows submitted to the IATF programs on a large scale.
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Keywords:
BULLS;
CASA SYSTEM;
FERTILITY;
FTAI;
SEMEN
Document Type: Regular Paper
Affiliations:
1:
LARAA, Universidade Estadual de Londrina- UEL, Brazil
2:
Veterinário Autônomo, Londrina, Brazil
3:
Departamento de pós graduação em Agronomia, Universidade Estadual de Londrina&hyphen UEL, Brazil
4:
Laboratório de Reprodução Animal, Universidade Estadual do Norte do Parana, Bandeirantes, Brazil
Publication date:
May 1, 2022
More about this publication?
CryoLetters is a bimonthly international journal for low temperature sciences, including cryobiology, cryopreservation or vitrification of cells and tissues, chemical and physical aspects of freezing and drying, and studies involving ecology of cold environments, and cold adaptation
The journal publishes original research reports, authoritative reviews, technical developments and commissioned book reviews of studies of the effects produced by low temperatures on a wide variety of scientific and technical processes, or those involving low temperature techniques in the investigation of physical, chemical, biological and ecological problems.