White leghorn hybrids (females) from a commercial hatchery split into two groups
Hatchery group (HC) (N=105)
- Incubated, hatched, vaccinated, and processed at the commercial hatchery
- Underwent approximately seven hours of transportation to the LiU research facilities
Control group (CC) (N=71)
- Newly laid eggs transported to LiU
- Incubated, hatched, and processed at LiU in concordant time with the HC group
Experimental timeline and procedures:
Over the experimental timeline, both groups were subjected to two different stressors that would be commonly experienced during their lifetime. The stress susceptibility to these two stressors was evaluated by a number of tests to measure both, physiological, as well as behavioral responses.
Tonic immobility procedure
- Measured the fear in regards to one hour of transport as a stressor
- Baseline recorded one day before the transportation
- Treatment recorded one day after the transportation
- Recorded values: number of inductions into tonic immobility (max. 3), first beep, first voluntary head movement, and the righting time
- The effects of transportation were analyzed, as well as the differences between the treatment groups.
Regrouping as a stressor
- Evaluated by one hour 1-0 group behavioral observations that were repeated three times: baseline before regrouping, immediately after the regrouping, and second baseline two days after regrouping. Observations were not analyzed statistically, but percentages of occurrences were compared.
- Evaluated by blood plasma corticosterone analysis, baseline two days before and treatment one day after regrouping. The effects of regrouping, as well as the intra-group differences, were analyzed.
- Since each experimental group was housed across two pens per treatment, half of each pen within the treatment was swapped.
- The difference between the treatment groups was analyzed for each weighing day.