Sperm morphometry and chromatin condensation in Nelore bulls of different ages and their effects on IVF

Sperm morphometry and chromatin condensation in Nelore bulls of different ages and their effects on IVF

The aim of this study was to evaluate the chromatin packing and sperm head morphometry of cryopreserved semen of Nelore bulls (Bos taurus indicus) of different ages. Furthermore, the influence of the degree of chromatin compaction on in vitro embryo production (IVP) was investigated. Forty bulls wer...

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Published in:Theriogenology Vol. 87; pp. 154 - 160
Main Authors: Kipper, B.H., Trevizan, J.T., Carreira, J.T., Carvalho, I.R., Mingoti, G.Z., Beletti, M.E., Perri, S.H.V., Franciscato, D.A., Pierucci, J.C., Koivisto, M. B
Format: Journal Article
Language:English
Published: United States Elsevier Inc 01-01-2017
Subjects:
Aging - physiology
Animals
Bovine
Cattle - physiology
Chromatin - physiology
Chromomycin A3
Fertility
Fertilization in Vitro - veterinary
Male
Semen
Spermatozoa - cytology
Spermatozoa - physiology
Toluidine blue
Toluidine blue
Chromomycin A3
Bovine
Fertility
Semen
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Summary:The aim of this study was to evaluate the chromatin packing and sperm head morphometry of cryopreserved semen of Nelore bulls (Bos taurus indicus) of different ages. Furthermore, the influence of the degree of chromatin compaction on in vitro embryo production (IVP) was investigated. Forty bulls were divided into three groups: young (1.8–2 years), adult (3.5–7 years), and senile (8–14.3 years). The ejaculates were frozen according to standards established by the Artificial Insemination Center located in the Southeast of Brazil. Toluidine blue staining was used for simultaneous evaluation of the sperm chromatin and sperm head morphometry. Chromomycin A3 (CMA3) was applied to analyze sperm protamination and IVP for embryonic development. Spermatozoa of young bulls presented higher values for area (A, pixels), perimeter (P, pixels), and width (W, pixels) compared to adults and senile (young: A = 1848.5 ± 119.79, P = 10.23 ± 0.29, and W = 1.95 ± 0.1; adults: A = 1672.9 ± 104.46, P = 9.86 ± 0.33, and W = 1.81 ± 0.06; senile: A = 1723.1 ± 124.41, P = 9.97 ± 0.33, and W = 1.83 ± 0.09; P < 0.0001) and showed higher protamination deficiency when analyzed by CMA3 (young: 1.57 ± 0.76; adults: 1.09 ± 0.63, and senile: 0.90 ± 0.59; P < 0.05). Likewise, variables of sperm head size (A, P, and W) and protamination assessed by CMA3 showed negative correlation with age and positive correlation with ellipticity, evaluated by toluidine blue method (P < 0.05). Sperm head area was larger in spermatozoa presenting chromatin instabilities than spermatozoa without chromatin alteration (P < 0.0001). There was no difference in IVP when using semen with larger or smaller portions of spermatozoa with chromatin instabilities, indicating that the proportion of sperm with abnormal chromatin compaction (4%–16.15%) did not interfere with early embryonic development. From our results, it can be concluded that sperm of young Nelore bulls have larger heads compared to adults and senile due to reduced protamine content when evaluated by CMA3 and higher proportion of major sperm defects assessed by differential interference contrast microscopy.
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ISSN:0093-691X
1879-3231
DOI:10.1016/j.theriogenology.2016.08.017