Reciprocal translocations in pigs. Their detection and consequences on animal performance and economic losses.

In France, the national computerized program for sow herd management regularly delivers a listing of hypoprolific boars for which a cytogenetic evaluation is required, and participates in the differential diagnosis of the other causes of reduced prolificacy. Two reciprocal translocations, 4/14 and 7/15, reducing the prolificacy by about 45 percent have been discovered since 1979. A third one, leading to a prolificacy reduction of about 28 percent, is described in the present paper. The effects of translocation 4/14 were studied in an experimental herd, in which the ovulation rate did not seem to be modified and the early embryonic mortality accounted for the decrease in litter size. The growth rate at day 35 was higher in piglets carrying the chromosomal abnormality than in their normal littermates, i.e., 215 vs. 182 g per day (P less than 0.10). The economic consequences of using a boar carrying a translocation on a group of 21 sows were estimated by means of a simulation model "Porsim." When prolificacy decreased by five piglets per litter, the losses represented 157 piglets, i.e., about $4000. If, in addition to this, the percentage of non-returns into heat decreased by 35 percent, the losses then represented 248 piglets, i.e., $6000. Because of this important economic risk, it is suggested that measures be taken to detect defective animals and to prevent their use.