Effect of perphenazine enanthate on open-field test behaviour and stress-induced hyperthermia in domestic sheep.

The open-field test (OFT) and stress-induced hyperthermia (SIH) have been used to measure individual differences in fear. The present study has been designed as a pharmacological validation of OFT and SIH as indicators of fear in sheep using perphenazine enanthate (PPZ), a long-acting neuroleptic. Twenty four ewes of two breeds, Lacaune and Ripollesa, were tested in an arena measuring 5mx2.5m. Treatment group received one dose of 1.5mg/kg of PPZ and control group received sterile sesame oil. All animals were tested for 10min and behaviours were recorded. Rectal temperature was measured at the beginning (T1) and at the end (T2) of the test. SIH was defined as the difference between T2 and T1. Sheep were tested on days 1, 2, 3, 4, 7 and 9 after PPZ injection. Variables were analysed using a mixed model. PPZ decreased bleats on days 2, 3, 4 and the SIH response on days 2 and 3. Breed differences were observed. Treated animals showed positive correlations between SIH and bleats; squares entered; attempts to escape and negative correlation between SIH and visits to the food bucket. Our results suggest that behaviour and SIH on the OFT are useful measures of fear in sheep.

Differences in open field behavior between heterozygous and homozygous negative gilts for the RYR(1) gene.

A test widely used to assess fear and novelty responses in domestic species is the open field. The aim of this study was to investigate the effect of RYR(1) genotype on open field behavior in growing pigs. The study subjected 15 heterozygous (Nn) and 15 RYR(1)-free (NN) gilts of 19 weeks of age to 3 replicates of an open field test 2 days apart from each other. The study measured the number of grid lines crossed and defecation score in the test arena. There was a significant individual correlation among the 3 replicates of the test, both for number of grid lines crossed and defecation score (p <.05). RYR(1) genotype had a significant effect on number of grid lines crossed, with NN gilts showing more overall activity than Nn gilts (p <.05). The study observed no significant differences in defecation score between genotypes. This result suggests that the RYR(1) genotype may have an effect on the appraisal of novelty. Thus, it would be interesting to take this factor into account when using this methodology to assess fear responses in pigs and in interpreting the results with respect to welfare.