The natural mating of a doe with a ram produced a female hybrid which had 57 chromosomes, including three metacentric autosomes. We believe this to be the first authenticated report of a sheep-goat hybrid in New Zealand.

In an analysis of the chromosomes in 1556 metaphase II figures from 26 translocation-carrying rams and 84 figures from 3 normal rams (54, XY), there were no hypermodal cells in the normal rams but 35 such cells in the translocation rams, giving mean aneuploid frequencies of 3.92 percent, 4.29 percent, and 5.29 percent for the rams heterozygous for 1, 2, and 3 translocations, respectively. The translocation chromosome in the heterozygous state was found to segregate evenly during meiosis. Although the effect of heterozygosity was to increase the aneuploid frequency of the ram it is seen that the frequency in all translocation-carrying rams is low and it is thought that these cells are eliminated during spermatogenesis and therefore do not reduce the fertility of the sheep.

We report two new Robertsonian centric fusions, designated t₄and t₅, in New Zealand Romney sheep. Q- and G-banding studies show that sheep chromosomes 5 and 8 are fused in t₄ and that chromosomes 8 and 22 are fused in t₅. The presence of large blocks of centromeric heterochromatin in t₄ and t₅suggests that the fusions may be of recent origin.

Chromosomal abnormalities have been detected in five mares identified by their poor reproductive performance. All had small gonads and absent or irregular oestrous cycles. One mare was 65, XXX, two were 64, XY sex-reversal females and two were sex chromosome mosaics with karyotypes of 63, XO/64, XX/64, XY and 63, XO/64, XX respectively. This report supports the suggestion made in earlier studies that sex chromosome abnormalities may be a significant cause of sterility in the mare.

Several mixed-sex twins were produced by red deer treated with progesterone and pregnant mare’s serum gonadotrophin. Of seven females karyotyped, two were 68, XX/68, XY chimeras. One male had the same chimeric karyotype as its female co-twin. These are the first reported cases of freemartinism in deer.