The assessment of the effect of presenting a companion's face picture on social isolation stress using saliva sampling in cows

The effect of presenting a companion's face picture on social isolation stress was assessed by saliva sampling in cows. Three Japanese Black test cows and another companion cow were used. At 09.00 hours, one of the test cows was housed in an experimental pen with the companion in a neighboring pen. At 11.30 hours, the test cow was socially isolated by taking the companion out the neighboring pen. At 12.00 hours, the test cow was exposed to one of four treatments until 15.00 hours; presenting a blank picture (P-Blank), a white-ground picture of the companion's face (P-Com) or an unfamiliar Holstein's face (P-Hol), or the companion in the neighboring pen and a blank picture (Com). The cows were randomly exposed to all treatments. The cows' saliva were sampled for measuring salivary cortisol and chromogranin A concentrations (Sa-Cort, Sa-ChA) at 11.30, 12.00, 12.30 and 14.00 hours. At 12.00 hours, Sa-ChA was higher than that at 11.30 hours (P < 0.01). At 12.30 hours Sa-ChA of Com and P-Com were lower than that of P-Blank (P = 0.09, P = 0.08). At 14.00 hours Sa-Cort of Com was lower than that of P-Blank (P < 0.01), but Sa-Cort of P-Com was higher than that of P-Blank (P < 0.01). It is suggested that P-Com might decrease isolation stress only a short time, but afterward induced stress in cows.