Semen quality of Nellore and Angus bulls classified by fertility indices and relations with field fertility in fixed-time artificial insemination

Camile Sanches Silva; Eliane Vianna da Costa-E-Silva; Margot Alves Nunes Dode; Andrielle Thainar Mendes Cunha; Wagner Rodrigues Garcia; Breno Fernandes Barreto Sampaio; Juliana Correa Borges Silva; Francisco Eduardo Machado Vaz; Karl Kerns; Peter Sutovsky; Eriklis Nogueira

doi:10.1016/j.theriogenology.2023.09.001

Semen quality of Nellore and Angus bulls classified by fertility indices and relations with field fertility in fixed-time artificial insemination

Theriogenology. 2023 Dec:212:148-156. doi: 10.1016/j.theriogenology.2023.09.001. Epub 2023 Sep 9.

Affiliations

¹ Programa de Pós-graduação em Ciências Veterinárias, FAMEZ/UFMS- Cidade Universitária, Caixa Postal 549, Postal Code- 79070-900, Campo Grande, MS, Brazil; Grupo de Estudos em Reprodução Animal - GERA-MS/CNPq, Brazil.
² EMBRAPA Cenargen- Parque estação biológica- PqEB, s/n. Postal Code 70770-901, Brasilia, DF, Brazil.
³ Universidade de Brasília, Instituto de Biologia Animal, Brazil.
⁴ Embrapa Pantanal, Rua 21 de Setembro n. 1880, Postal Code- 79320-900, Corumba, MS, Brazil.
⁵ Programa de Pós-graduação em Ciências Veterinárias, FAMEZ/UFMS- Cidade Universitária, Caixa Postal 549, Postal Code- 79070-900, Campo Grande, MS, Brazil.
⁶ Division of Animal Sciences, University of Missouri, Columbia, MO, 65211, USA; Department of Animal Science, Iowa State University, Ames, IA, 50011, USA.
⁷ Division of Animal Sciences, University of Missouri, Columbia, MO, 65211, USA; Department of Obstetrics, Gynecology and Women's Health, University of Missouri, Columbia, MO, 65211, USA.
⁸ Programa de Pós-graduação em Ciências Veterinárias, FAMEZ/UFMS- Cidade Universitária, Caixa Postal 549, Postal Code- 79070-900, Campo Grande, MS, Brazil; Embrapa Pantanal, Rua 21 de Setembro n. 1880, Postal Code- 79320-900, Corumba, MS, Brazil; Grupo de Estudos em Reprodução Animal - GERA-MS/CNPq, Brazil. Electronic address: eriklis.nogueira@embrapa.br.

PMID: 37722295
DOI: 10.1016/j.theriogenology.2023.09.001

Abstract

Despite being the most important form of biotechnology in animal reproduction, artificial insemination was used in about 23% of Brazilian bovine herds in 2021. This is due to the variability of results caused by varying bull fertility and body condition of the cows. This study aimed to correlate the fertility indices of bulls with qualitative attributes of the semen. Semen samples from 28 bulls (Nellore and Angus) were used to evaluate postthaw sperm morphology and kinetics using conventional analysis, image-based flow cytometry (IBFC) and computer-assisted semen analysis (CASA). The fertility index was effective in separating bulls into 4 different fertility classes (P < 0.001), and fertility rates in timed artificial insemination (TAI) remained constant between the cows' fertility categories (P < 0.001) and in the different grades of female body condition (P < 0.005). After partial least squares regression (PLS) analysis, four models were proposed with different variables. The coefficients of determination for the conventional analysis, CASA, and IBCFC models were 0.154, 0.380, and 0.259, respectively. The composite model, including select IBFC and CASA parameters, showed a greater R² (0.481) with progressive motility, average speed (VAP, μm/s), membrane integrity, and mitochondrial potential, showing a positive effect. Linear speed (VSL, μm/s) and acrosomal integrity had a negative effect on bull fertility indices. Bulls classified by the fertility index attained dispersed pregnancy rates in different cow body condition score (BCS) classes, and the sperm quality pattern was consistent with this classification. In conclusion, this novel composite model including CASA and IBFC parameters improves the prediction of bull fertility used in TAI.

Keywords: CASA; Flow cytometry; Nellore cows; Pregnancy; sperm.