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Unformatted text preview: (by using four randomly positioned Tiny Talk data loggers in each house at a height of 60 cm); and atmospheric ammonia (by a Gastec GV-100S pumpset), light at bird height (ISO-Tech digital light meter) and litter moisture content ([sample weight difference after drying/sample weight] 100) at target density. Birds We recorded the source, breed, sex (all-male, all-female or mixed), age of parent flock, date and time of arrival, position of chicks on delivery lorry, type of vehicle (rigid or articulated), ventilation (fans, vents) and on-board temperature. The numbers of trays of chicks per house and chicks per tray were audited. Leg health At target density, a single bird chosen at random from each of ten points in each house, was observed walking for at least ten paces before being scored for gait (Table 1, n 1,140 birds). Groups of ten birds were subsequently caught at four random points per house; individuals were inverted (ventral side facing handler), held by the legs with the handlers thumbs just below the intertarsal joint and assessed for leg straightness (Table 1, n 4,370), weighed and then released. Corticosteroid measurements Fresh faecal samples were collected at five random positions in each house, dried at 40 8 C and analysed for corticosterone 19,20 . Behaviour Four battery-operated video cameras radio-linked to a VCR (Tracksys) were placed in each house at a height of 155 cm. Eight 10-min sequential records of each camera view were made between 10:00 and 12:00 at target density. One randomly chosen focal bird from each 10-min section of video was analysed for 5 min for frequency and duration of stand, lie, feed, drink, preen, rest (eyes closed) and lie stretched out; frequency of walk (including number of strides) and peck litter, peck other bird, scratch litter, scratch head, stretch head, wing or leg, shake body, shake head, dust bathe, wing flap, aggressive interactions and perch; changes of posture (up or down); jostling or being jostled by other birds; and being disturbed or walked on by other birds ( n 741 from 107 houses). Production We recorded mortality (numbers of birds found dead plus numbers of birds culled because of illness or leg problems), feed conversion ratio, water intake, date, numbers and weights of birds removed from the house (thinned or cleared) and number of birds rejected at the processing plant. Growth rate was calculated as: individual weight(average chick weight)/ number of days. Statistical analysis The independent statistical unit was house. Where many measurements were made per house, a single mean-per-house value was used in the analysis. Variables were first analysed for effects of target stocking density, actual stocking density and company by analysis of variance. Where actual density effects were significant, they were further analysed by regression analysis (fitted line model) and post-hoc Tukey comparison....
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This note was uploaded on 07/12/2011 for the course BIO 620 taught by Professor Hardy during the Spring '11 term at University of Florida.
- Spring '11