Identification of sexually low-response rams using libido test and their performance when allowed to mate under field conditions

Thirty-one Ile de France stud rams raised in monosexual groups were evaluated for sexual behaviour using three 10-minute libido tests. Rams represented two age (± SD) groups namely, 455,2 ± 6,7 (n = 10) and 352,9 ± 11,0 (n = 21) days respectively. The proportion of rams which completed service did not increase significantly over the three tests. Eight (25,8%) of the rams did not attempt to serve in any of the tests, and were termed sexually low-response. Five of these rams had a common sire. The low-response rams were mated to small flocks of ewes under pasture conditions, and two of the rams remained sexually inactive.