ABSTRACT
The synaptonemal complex (SC) of specimens of Bos taurus taurus from the Holstein-Friesian, Piemontese, and Simmental breeds, was analysed. The analysis included quantification of the frequency of various types of abnormalities in the SC, and the frequency of cells with SC abnormalities. All animals had 29 autosomal bivalents and one sexual bivalent and the most frequently recorded abnormality was pairing failure. The number of cells with abnormalities in the Holstein-Friesian breed was 29.41%, in the Piemontese breed was 30.00% and in the Simmental breed it was 29.54%. The subspecies Bos taurus taurus had 29.63% of cells showing abnormalities with 57.33% of these abnormalities occurring in zygotene and 42.67% occurring in pachytene. Statistical analyses showed that there were no significant differences in the number of cells with SC abnormalities among the breeds studied. The frequency of cells with abnormalities, and the efect on the fertility of the Holstein-Friesian, Piemontese and Simmental breeds are discussed.
Subject(s)
Cattle/genetics , Chromosomes/ultrastructure , Synaptonemal Complex/ultrastructure , Animals , Brazil , Breeding , Cattle/physiology , Chromosome Aberrations , Male , Spermatocytes/cytologyABSTRACT
The synaptonemal complex (SC) was analyzed in four F1 hybrids of Bos taurus taurus and B. taurus indicus including Gyr-Simmental (G-S), Nelore Simmental (N-S), Gyr-Holstein-Friesian (G-H) and Nelore-Piemontese (N-P). We analysed the frequency of various types of SC abnormalities and the frequency of cells with SC abnormalities. The results were compared with similar observations made on purebred animals. All the animals studied possessed 29 autosomal and one sex bivalent. The frequency of cells with abnormalities in the hybrids were 28.0% in the N-P, 29.1% in the G-S, 33.3% in the N-S and 40.0% in the G-H. The frequency of cells with abnormalities in the four hybrids was 31.5%; 57.9% of these abnormalities occurred in zygotene and 42.0% occurred in pachytene. The comparisons among the hybrids and among the hybrids and their parental breeds showed that the only significant difference was between Gyr and Gyr-Holstein-Friesian animals. Some aspects of the relationship between the frequency of cells with anomalies and the fertility of hybrids are discussed.
