Abstract
Broiler breeders, the parent stock of meat chickens, are feed-restricted throughout the production cycle to avoid obesity-related problems in their health and reproductive performance. Broiler breeders often show signs of chronic hunger, lack of satiety and feeding frustration, and the development of alternative feeding strategies has investigated the inclusion of calcium propionate (CaP) as an appetite suppressant. The mechanisms involved in the reduction of voluntary feed intake are unknown, but are thought to be due to low palatability, gastrointestinal discomfort, or both. The objective of this experiment was to examine the effect of CaP as an appetite suppressant on the experience of a negative affective state, using a conditioned place preference test. Twenty four broiler breeders were trained to associate the consumption of CaP or a placebo pill with a red or blue place, depending on inherent colour preference. Pullets consumed two pills followed by 20 g feed allotment. The CaP pill contained 160 mg of CaP and the placebo pill had 160 mg of feed. Conditioning lasted for 90 min/pullet/day over 8 consecutive days at 7 and 9 weeks of age, and pullets’ choice was tested in a T-maze twice on two consecutive days at both 8 and 10 weeks of age. Data were analysed using a linear mixed regression model, with pen nested in the model and age as a repeated measure. Pullets were less likely to choose the place conditioned with the consumption of CaP (P<0.05) and the preference of the placebo linearly increased with training sessions (P<0.05). These results suggest that calcium propionate as an appetite suppressant can induce a negative affective state, reducing feed intake in broiler breeders fed CaP diets by causing an avoidance response rather than satiety.
Highlights
Our results indicate that pullets avoided the place conditioned with the consumption of calcium propionate (CaP) and developed preference for the placebo place over time
This study demonstrates the causal effect of CaP on inducing a negative affective state at an inclusion rate proven to decrease voluntary feed intake in poultry
In agreement with our results, CaP can induce a negative affective state regardless of its palatability, CaP may have an additional effect at reducing voluntary feed intake due to low palatability [21]
Summary
A total of 24 Ross 308 broiler breeder pullets were used for this experiment donated at one day of age courtesy of Aviagen (via Horizon Poultry, Hanover, Ontario, Canada). Day-old chicks were infrared beak treated and vaccinated based on local recommendations (i.e. infectious bronchitis and Marek’s disease), and chicks were subsequently raised at the OMAFRA Arkell Poultry Research Station (Guelph, ON, Canada). Chicks were distributed upon arrival to six cages (10.3 chicks/m2) and were relocated at 22 days of age to six floor pens (4 pullets/pen at 0.85 pullets/m2). Floor pens (1.7 m wide x 2.0 m deep x 1.2 m high) had wood shavings as bedding and water was available ad libitum from a 5-nipple drinker. Chicks were on target body weight at 22 days of age and were individually wing tagged
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