Reproductive potential in female cattle discarded as infertile.

Dairy cattle were served at consecutive heats up to three times each; they were then slaughtered, and the genital tracts were examined. Seventy-four cattle had been discarded from herds because they had not bred; 14 had never calved, and 14 were primiparous. Of these 28 animals, 12 (43%) conceived readily, and had normal pregnancies; normal genital tracts were found at slaughter. Eleven of the 16 animals that did not conceive had normal genitalia. The remaining 46 animals were mature cows, with a mean parity of 4-9; 9 (19-6%) became pregnant and had live embryos at autopsy, while in 7 other cows (15-2%) conception had been followed by embryonic death. Five of the uteri associated with these 16 conceptions showed pathological changes. Thirty of the 46 mature cows (65%) did not conceive; 12 (40%) had normal genitalia, and 18 (60%) showed severe pathological changes in the uterus and/or oviduct. Nine 'control' cows discarded because of poor milk yield were infertile, but 5 cows, discarded for various other reasons, all bred normally.