Visual access to an outdoor range early in life, but not environmental complexity, increases meat chicken ranging behavior

Abstract

Not all chickens access an outdoor range when the opportunity is provided. This may be related to the abrupt change in environments from the stable rearing conditions to the complexity of the outdoor range. We aimed to prepare chickens to range by increasing the complexity of the indoor environment early in life with the intention to encourage range use. Mixed sex Cobb500 chickens were allocated to 1 of 3 treatment groups: visual access (VA) treatment provided VA to the outdoor range from day old via transparent pop-hole covers; environmental complexity (EC) treatment provided an artificial haybale, fan with streamers and a solid vertical barrier; Control treatment was a representative conventional environment. Chickens were given access to the outdoor range at 21 d of age. Behavior in the home pen was assessed in wk 1, 2 and 5 and individual ranging behavior was monitored through radio frequency identification (RFID) technology. The VA chickens were more active compared to EC (P = 0.006) and Control (P = 0.007) chickens and spent more time foraging than control chickens (P = 0.036) during the first week of life. More VA chickens accessed the range area compared to EC chickens (P = 0.015). VA chickens accessed the range sooner after they were first provided access and spent more time on the range than EC and control chickens (P < 0.001). Mortality was lower in the VA treatment compared to EC (P = 0.024) and control group (P = 0.002). There was evidence that VA chickens weighed less than Control and EC chickens, however results were inconsistent between age and sex. Hence, providing meat chickens with VA to an outdoor range early in life increased activity in early life, decreased latency to first access the range and increased time on the range and lowered mortality. Future work should aim to understand the mechanism behind these changes in behavior to develop recommendations for producers to implement in commercial conditions.

Keywords: activity; environmental enrichment; free-range; natural light; rearing.

Figure 1

Pen locations outlined for behavioral sampling. The divisions were only theoretical; there were no physical markers in the pens. The areas were the same for all pens, however the diagram on the left shows which enrichment item were associated with each zone for chickens provided with environmental complexity chickens, relative to chickens provided with visual access to the outdoor range and control chickens which is outlined in the diagram on the right.

Figure 2

Proportion of chickens within a pen that were found in zone 1 (back of pen near entry door), zone 2 (containing the feeder), zone 3 (containing the brooder), zone 4 (containing a haybale for chickens provided with environmental complexity (EC chickens) but nothing for control and chickens provided with Visual Access to the outdoor range during rearing (VA chickens)) and zone 5 (adjacent to the pop hole, which was solid for EC and control chickens but transparent for VA chickens) during wk 1 (top) wk 2 (middle) and after range access was provided in wk 5 (bottom).

Figure 3

Behavioral time budgets for chickens in control environments (grey solid bar), with visual access to an outdoor range (orange striped bar) or with environmental complexity (white bars with black dots) during wk 1 (top graph), wk 2 (middle graph) and wk 5 when the range doors were open (bottom graph). Data are presented as the average proportion of chickens in a pen performing each behavior at 1 scan sampling interval (i.e., each hour between 6:00 and 22:00). Differing subscript indicates a difference between treatment groups for a particular behavior (P < 0.05).

Figure 4

Survival curve indicating the proportion of chickens that did not access the outdoor range and the latency for chickens to access the range (days) for chickens raised in a standard environment (control, solid grey line), with visual access to the range (VA, orange dash lined) or environmental complexity (EC, black dotted line). Differing subscript indicates a difference in the proportion of chickens that accessed the range and the latency to range (P < 0.05).

Figure 5

The avereage number of days (left) and hours (right) an individual spent on the range throughout the experiment (maximum of 21 d). Differing subscript indicates a difference between treatment groups (P < 0.05).

Figure 6

Weekly mortality for chickens reared in a control environment (solid grey line), with visual access to an outdoor range (orange dashed line) or environmental complexity (black dotted line).