Reproductive tract score 1 had a Sp of at least 94% for 24-day anoestrus or
pregnancy failure during the first breeding season. In other words, had heifers with RTS 1
been culled from the herd, 94% of heifers that were observed in oestrus during the first 24
days or that became pregnant (equating to absence of the conditions tested for) would
have been retained in the herd due to the fact that they had a RTS higher than 1.
Increasing the cut-off to RTS 2 decreased the Sp by between 18 and 32%. The PV+ of
low RTS for 24-day anoestrus and pregnancy failure varied, depending on the average
pregnancy results in that year (Table 6).