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Cytogenetic survey of Holstein bulls at a commercial artificial insemination company to determine prevalence of bulls with centric fusion and chimeric anomalies

Brad E. Seguin DVM, PhD, DACT1, Ting Q. Zhang DVM, PhD2,3, Lance C. Buoen BA4, Alvin F. Weber DVM, PhD5, and George R. Ruth DVM, PhD, DACVP6,7
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  • 1 Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 2 Department of Veterinary Diagnostic Medicine, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 3 Present address: 2054 Brewster St, St Paul, MN 55108.
  • | 4 Department of Veterinary Diagnostic Medicine, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 5 Department of Pathobiology, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 6 Department of Veterinary Diagnostic Medicine, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 7 Present address:12099 Lake Blvd, PO Box 397, Lindstrom, MN 55045.

Abstract

Objective—To determine prevalence of Holstein bulls with chromosomal anomalies, particularly the 1/21 centric fusion (CF), at a commercial artificial insemination (AI) company in the United States.

Design—Cross-sectional cytogenetic prevalence study.

Animals—All 606 Holstein bulls at a commercial AI company were cytogenetically screened to detect CF, chimerism, and other chromosomal abnormalities.

Procedure—Lymphocytes from heparinized blood samples were cultured by standard cytogenetic techniques, and chromosome spreads were prepared for microscopic examination. Chromosomal abnormalities were detected by examining 10 chromosome spreads per bull. Pedigree analysis was performed.

Results—None of the bulls had any type of CF. However, 6 bulls were identified as chimeras (ie, contained lymphocytes with male [XY] and female [XX] chromosomes). One bull was sire or maternal grandsire to 85 of the bulls tested, and 739 of 1,212 (61%) sire and maternal-grandsire possibilities were accounted for by just 18 bulls.

Conclusions and Clinical Relevance—Analysis of these results supports previous indications that CF is extremely rare in Holstein bloodlines available commercially via AI in the United States. However, chimeric bulls are more common, and they reportedly have decreased reproductive performance. Therefore, identification of chimeric sires in the AI facility reported here and the possibility of de novo onset of CF at any time indicates that early cytogenetic screening should be encouraged for prospective bulls intended for use in AI programs. ( J Am Vet Med Assoc 2000;216:65–67)

Abstract

Objective—To determine prevalence of Holstein bulls with chromosomal anomalies, particularly the 1/21 centric fusion (CF), at a commercial artificial insemination (AI) company in the United States.

Design—Cross-sectional cytogenetic prevalence study.

Animals—All 606 Holstein bulls at a commercial AI company were cytogenetically screened to detect CF, chimerism, and other chromosomal abnormalities.

Procedure—Lymphocytes from heparinized blood samples were cultured by standard cytogenetic techniques, and chromosome spreads were prepared for microscopic examination. Chromosomal abnormalities were detected by examining 10 chromosome spreads per bull. Pedigree analysis was performed.

Results—None of the bulls had any type of CF. However, 6 bulls were identified as chimeras (ie, contained lymphocytes with male [XY] and female [XX] chromosomes). One bull was sire or maternal grandsire to 85 of the bulls tested, and 739 of 1,212 (61%) sire and maternal-grandsire possibilities were accounted for by just 18 bulls.

Conclusions and Clinical Relevance—Analysis of these results supports previous indications that CF is extremely rare in Holstein bloodlines available commercially via AI in the United States. However, chimeric bulls are more common, and they reportedly have decreased reproductive performance. Therefore, identification of chimeric sires in the AI facility reported here and the possibility of de novo onset of CF at any time indicates that early cytogenetic screening should be encouraged for prospective bulls intended for use in AI programs. ( J Am Vet Med Assoc 2000;216:65–67)