Detection of oestrous-related odour in ewe urine by rams.

The ability of rams to discriminate between urine odour of oestrous ewes and urine odours from ewes at other days of the oestrous cycle was determined using operant conditioning techniques. Rams could discriminate between the odour of urine of oestrous ewes and the odours of urine from ewes at day 6 to day 1 before oestrus and from ewes at day 4 to day 10 after oestrus. Rams did not discriminate between odours of urine samples from different ewes in oestrus, or between urine odour of oestrous ewes (day 0) and urine odours from ewes at day 1 to day 3 after oestrus. These results support the hypothesis that ewes in oestrus produce an odour in urine that is detectable by rams.