Short communication A note on the effect of individual housing conditions on LH secretion in ewes after exposure to a ram J.A. Abecia * , F. Forcada, O. Zun Äiga Departamento de Produccio Ân, Animal y Ciencia de los Alimentos. Facultad de Veterinaria, Miguel Servet 177, 50013 Zaragoza, Spain Accepted 20 September 2001 Abstract To determine whether it is feasible to use the stimulus of exposure to a ram to induce sexual activity in individually housed ewes, 33 adult anoestrous ewes were randomly allocated to two treatments: Group 1, n  20, housed in individual pens, with a ram's pen situated between every two ewes exposed to rams through the pen's bars) and Group 2, n  13, housed in a communal pen with ®ve rams full contact with the rams). The day before the introduction of rams, blood samples were collected from Group 1 ewes, for 6 h at 15 min intervals commencing 10:00 h. Rams were introduced in both groups the following day at 8:00 h. Two hours later, blood samples were collectedfromGroup1ewesfor6hat15minintervals.Thereafter,ewesandramsweremovedtoa communal pen and blood samples collected every 3 h until 10:00 h the next day. In Group 2, blood samples were collected every 3 h for 24 h starting at 10:00 h, 2 h after the rams were introduced. From the samples collected at 15 min intervals, no differences between mean LH concentrations, pulse frequencies and amplitudes before or after the introduction of rams were observed in Group 1. The percentage of ewes presenting a pre-ovulatory surge of LH in the ®rst 24 h after the introduction of rams was similar in both groups Group 1: 50%, 10 ewes; Group 2: 61.5%, 8 ewes). The pre-ovulatory LH surges began approximately 7 h later P  0:05) in Group 1 than in Group 2 18:5  2:2hversus11:8  2:6 h, respectively). Mean plasma LH concentrations were signi®cantly higher in Group 2, during the ®rst 8 h after the introduction of rams, these differences disappeared when all the animals were moved to the communal pen. In conclusion, individual housing together with frequent blood sampling conditions do not induce a signi®cant increase of LH secretion of anoestrous ewes after a ram effect, as compared with that in rams and ewes in communal pens. Further experiments are necessary to separate, on one hand, the effect of housing and on the other hand, the effect of sampling frequency on LH secretion after a ram effect. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Sheep; Ram effect; LH Applied Animal Behaviour Science 75 2002) 347±352 * Corresponding author. Tel.: 34-9-767-61000; fax: 34-9-767-61612. E-mail address: alf@posta.unizar.es J.A. Abecia). 0168-1591/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0168-159101)00202-7