[The frequency of chromosome abnormalities in farm animals and their economic consequences]

Examinations during the last two decades of the chromosome complements of various species of domestic animals have revealed the existence of a considerable number of abnormalities, including inherited rearrangements: approximately 20 in cattle, 15 in pigs (predominantly reciprocal translocations), 3 in sheep, 2 in horses (predominantly monosomy X), and 1 in goats. (The accumulation of data on the frequency of such abnormalities and evaluation of their effects on reproductive performances of carriers of inherited rearrangement depends on a number of factors including the use of artificial insemination, number or progeny per sire or dam, and differences in generation intervals of the species concerned). The economic value of the cytogenetic findings depends on the degree of exchange of information between the breeders and the cytogenetics laboratories. An example of a successful collaboration is a Swedish study of a centric fusion translocation in Swedish Red and White cattle, one that affects chromosomes 1 and 29. There, the fertility-reducing effects of the translocation led to a loss of approximately $250,000. Recognition of the significance of the translocation prompted a search for carrier bulls and their elimination from the artificial insemination units. In swine, in which artificial insemination is used much less than in cattle, data on the frequency of reciprocal translocations in general must be obtained from the farms themselves. The main effect of an inherited chromosome rearrangement is a reduction in the number of offspring, perhaps to 50%, i.e., five piglets per litter.(ABSTRACT TRUNCATED AT 250 WORDS)