Fertility investigations in the Fsub1/subhybrid and backcross progeny of cattle (iBos taurus/i) and yak (iB. grunniens/i) in Mongolia

摘要

Investigations conducted in Mongolia into the sterility of the male khainag, an F1 hybrid animal resulting from crossing cattle (Bos tαurus, 2n = 60) with yaks (B. grunniens, 2n = 60), are reported. Reduced numbers of spermatogonia appear to characterise the testicular tubules of the khainag, and despite the identical cytological appearance of the two parental karyotypes, synaptic anomalies are seen at meiotic prophase in primary spermatocytes. The female khainag is fertile and can be backcrossed to cattle or yak bulls to produce a B1 backcross animal, the ortoom. Further backcrossing of ortoom females to cattle or yaks will yield a B2 backcross animal, the usanguzee. The impression is gained of better meiotic pairing in the backross animals than in the khainag. The “Haldane Rule” is followed perfectly by the cattle × yak hybrid; namely, sterility is confined to the