Birds, including chickens, see in a broad range of the colour spectrum and some colours can be stimulatory. A recent study in the United States (US) set out to determine whether colouring feed could stimulate broiler chickens to consume more.
all sections of the visible light spectrum and some ultraviolet colours, and it has been reported that simple tasks by birds, such as pecking, can be influenced by colour and be utilised to increased interest in a particular food item.
Although somewhat inconsistent, previous research has demonstrated that feed colour has the potential to increase or decrease feed consumption in broilers, thus affecting bodyweight gain during the growing period.
H Khosravinia observed that broilers consumed significantly more feed with green lighting and green feed over other light and feed combinations. Additionally, JB Cooper explored feed colours in turkeys and reported that the birds preferred green colours, as indicated by their strong acceptance of green feed.
White leghorns were tested on their response to red, yellow, green and blue feed colours, favouring blue feed the most and red the least, with red feed significantly decreasing feed consumption. By Natalie Berkhout In contrast, Leslie et al. found that when broiler chicks were given a choice between a non-coloured and coloured feed, they preferred non-coloured diets.
Broiler feed colour trials
To expand the base of knowledge related to the colouration of poultry feed, research was undertaken by the School of Agriculture at the Middle Tennessee State University in the US to assess how altered feed colour might impact the performance of broilers grown to 21 days of age. Primary and secondary colours were selected for this research, representing longer (red, orange, yellow, green) and shorter wavelengths (blue and purple).
Two trials were conducted to determine feed colour effects on broiler performance. Trial 1 included four treatments, namely control (complete broiler starter diet), red, green and blue. Trial 2 also comprised four treatments, namely control, orange, yellow and purple.
Dietary colour treatments consisted of added non-nutritive human food-grade powdered dyes. Control diets had a no dye inclusion. Each treatment (60 birds per treatment) was fed to 240 male Cobb 500 broilers during a 21-day grow-out, and data was analysed.
Results and discussion
For trial 1, little effects of feed colour on bird performance were recorded. Most observed differences appeared to reside with feed colour effects on feed conversion. Red and green feed depressed the adjusted feed conversion ratio (AFCR) from day 1 to 21 by 3,2 and 2,4% (p <0,05), respectively, compared to the control diet.
A similar effect from red feed was seen for AFCR between day 1 and 14, with a 2,6% increase compared with the control (p <0,05). Interestingly, birds that consumed the blue feed had a similar AFCR to control birds at every time period. However, no other performance parameters differed across treatments in this trial. Similar to the results of trial 1, trial 2 showed minimal influences of orange, yellow or purple feed on overall bird performance compared with the control diet.
However, some interesting effects were detected. The bodyweight gain (BWG) between day 1 and 14 of birds consuming the purple feed was 6,4% higher than birds consuming the yellow feed (p <0,05). A similar trend was observed for BWG from day 7 to 14 (p <0,05). Broiler performance results from this study suggest that feed colour effects are inconsistent, but do not indicate an aversion to certain colours.