Effects of (artificial) boar stimuli on uterine activity in estrous sows R. Gerritsen * , P. Langendijk, N.M. Soede, B. Kemp Adaptation Physiology, Animal Sciences Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands Received 17 August 2004; received in revised form 14 March 2005; accepted 14 March 2005 Abstract This study aims to examine influences of specific boar stimuli on uterine activity in estrous sows, by comparing uterine activity in presence of a mature teaser boar and a robot boar with variable stimuli. Nineteen multiparous, cyclic, commercial crossbred sows were used. Intra-luminal uterine pressure was measured using a non-surgical method for 45 min before applying one of four treatments in combination with a back-pressure-test (BPT): (1) robot with olfactory and auditory stimuli (R + O + A) (n = 16), (2) robot with auditory stimuli (R + A) (n = 16), (3) robot without additional stimuli (R) (n = 16), (4) a mature boar (boar) (n = 15). After treatment, measurements continued for 30 min. For each measurement, frequency, mean amplitude and mean duration of uterine contractions were determined. Spontaneous frequency of uterine contractions was 18.6 0.7 h À1 on average and did not differ between treatments. Frequency of contractions increased significantly for the boar (+5.6 1.3 h À1 ; P < 0.01), R + O + A (+3.9 1.3; P < 0.01) and R + A (+2.6 1.3; P < 0.05). The effect of boar presence on frequency of contractions was greater than the effect of R (P < 0.05). Amplitude and duration of contractions were not affected by treatment. The change in frequency was dependent on spontaneous frequency (P < 0.01). In conclusion, the higher the level of boar stimuli, the greater the increase in frequency of uterine contractions. The results indicate that the used combinations of artificial boar stimuli do not mimic a ‘whole’ boar. It is unclear which boar stimuli stimulate maximal uterine activity during estrus. # 2005 Elsevier Inc. All rights reserved. Keywords: Sow; Uterine activity; Boar; Pheromones; Auditory stimulus www.journals.elsevierhealth.com/periodicals/the Theriogenology 64 (2005) 1518–1525 * Corresponding author. Tel.: +31 317 483582; fax: +31 317 485005. E-mail address: rosemarijn.gerritsen@wur.nl (R. Gerritsen). 0093-691X/$ – see front matter # 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.theriogenology.2005.03.014