Most cows are bred to be exactly alike but with increased demand for dairy, many of these cows are housed in large dynamic groups, with little thought placed on how they deal with these settings.
Sure researchers focus on the aggressive behavior of the cows, after all, they don't want any injuries, but they haven't done much work on whether they are stressed out over sharing their housing with other cows.
With two large-scale dairies that house 3,000 to 8,000 cattle becoming the norm, researchers at The University of Northhampton, led by postgraduate Krista Marie McLennan, set out to see how bovine deal with their cow counterparts.
Younger cattle form stronger bonds
The researchers observed a herd of 400 Holstein-Friesian cattle in a cubicle and found social bonds formed between individual cows. Relying on previous trials, the scientists concluded spending 25% or more time with a particular cow was indicative of a preferred partner.
The researchers found the strongest bonds were formed when the cattle were younger. Between the ages of seven and eleven months, the cows exhibited the most positive social behavior and the strongest relationships between two of them. As the cattle got older, the relationships between pairs were much weaker.
Cattle get stressed when separated from their preferred partner
To gauge how strong the bond was between the preferred partners, the scientists removed one of the cows from the herd for a period of thirty minutes. When the cattle were separated from their preferred partner the heart rate of the cattle dropped significantly. When they were paired back up, they exhibited less agitation than when they were with their non-preferred partner.
"These results suggest that cattle were receiving social support from their preferred partners allowing them to have a reduced stress response to the social isolation test," wrote McLennan in the research report. "As cattle aged and experienced regrouping, positive social bonds tended to disappear and cattle were more likely to have only weak associations. During long term separation (two weeks) from preferred partners, cattle showed significant behavioural, physiological and milk production changes. Upon subsequent reunion of preferred partners and consequential regrouping of individuals, no further changes in behaviour, biology and milk production were observed, suggesting that separation rather than regrouping elicited a stress response."