EFFECT OF AGE AND PRESENCE OF PERCHES DURING REARING ON TONIC IMMOBILITY FEAR REACTIONS OF BROILER BREEDER PULLETS

Broiler breeders were housed in pens in an all-litter house with an 8- h photoperiod from hatching to 20 wk of age. They were reared either i n the presence or absence of perches (7 cm per bird) and on either a 1 4% or a 17% CP diet. The duration of the tonic immobility (TI) fear re sponse was measured in 15- and in 20-wk-old birds; each pullet was tes ted individually and once only. There was an apparent age-related incr ease in the duration of TI, which was attenuated by the provision of p erches during rearing. The results are discussed in terms of maturatio nal and environmental influences on the development and alleviation of fear.