Effect of enrichment with hemp seeds on the behaviour of laying hens in a cage-free system

The present study evaluated the effect of hempseed supplementation over the diet as an envi-ronmental enrichment on behaviour of laying hens. A 4-weeks trial run with 1800 Hy-line Brown laying hens, from 37 to 40 weeks of age, randomly allocated in 8 pens of an experimental aviary. Whole hempseeds were distributed (10% of the daily feed intake) in additional manual feeders in two pens or directly on the litter in other two pens, once a day at the same hour (10:00 a.m.), whereas no enrichment was provided in the other 4 pens. Hen behaviour was assessed through the analysis of 4 days of video recordings (one day per week) by scanning 10 sec every 30 min for every hour to score the number of hens on the floor, pecking the feeder, pecking the litter, moving, preening, dust-bathing, aggression, piling, inactive. Data were submitted to ANOVA with hemp seeds enrichment and hour of observation as main effects and the pen as a random effect, using the PROC GLIMMIX of SAS. The enrichment with hemp seeds in the feeder was obviously associated to a rate of animals pecking the feeder (7.37% of observed hens), which corresponded to a decreased preening in the same pens compared to those that received hemp seeds on the litter or did not receive any enrichment (11.5% vs. 15.3% and 19.7% of observed hens, respectively; P<0.001). In the same pens receiving hemp seed in the feeders, a higher rate of piling hens was observed compared to the group with hemp seed distributed on the litter and that without enrichment) (5.58% vs. 4.37% and 2.42% observed hens; P=0.01). Other behaviours were not modified by the environmental enrichment. As for changes according to the hour of observation, the highest number of hens on the ground was observed around 9:00 a.m. (43.8% of observed hens), when people entered the farm for daily recordings, ranging from 24.3% to 41.7% at the other observation hours. The rate of hens pecking the ground increased after switching on the lights and remained high until 8:00 a.m. when it started to decrease; then, it increased again from 11:00 a.m. until the end of daylight, which was negatively associated to the rate of inactive animals. Dust bathing showed a peak between 11 a.m. and 12:00 a.m., whereas preening was especially observed at the same hours besides 2 hours after switching on the light. In conclusion, the enrichment with hemp seeds did not substantially change the behaviours of animal, except for the opportunities of feeding alternative to the commercial diets. It should be further proved that the higher rate of piling hens in pens receiving hemp seeds, especially at the time of the entrance of people in the farm, could be considered an anticipatory behaviour eventually associated to a positive effect of the enrichment on hen affective status.