Conditioned place avoidance using encapsulated calcium propionate as an appetite suppressant for broiler breeders Conditioned place avoidance and calcium propionate

Abstract

<300) 11 Broiler breeders, the parent stock of meat chicks, are feed-restricted throughout rearing to avoid 12 obesity-related problems in their health and reproductive performance. Broiler breeders often 13 show signs of chronic hunger, lack of satiety and feeding frustration, and the development of 14 alternative feeding strategies has investigated the inclusion of calcium propionate (CaP) as an 15 appetite suppressant. However, the mechanisms involved in the reduction of voluntary feed 16 intake are unknown, but are thought to be due to low palatability, gastrointestinal discomfort, or 17 both. The objective of this experiment was to examine the effect of CaP as an appetite 18 suppressant on the experience of a negative affective state, using a conditioned place preference 19 test. Twenty four broiler breeders were trained to associate the consumption of CaP or a placebo 20 pill with a red or blue place, depending on inherent colour preference. Pullets consumed two pills 21 followed by 20 g feed allotment. The CaP pill contained 160 mg of CaP and the placebo pill had 22 160 mg of feed. Conditioning lasted for 90 min/pullet/day over 8 consecutive days at 7 and 9 23 weeks of age, and pullets' choice was tested in a T-maze twice on two consecutive days at both 8 24 and 10 weeks of age. Data were analysed using a linear mixed regression model, with pen nested 25 in the model and age as a repeated measure. Pullets were less likely to choose the place 26 conditioned with the consumption of CaP (P<0.05) and the preference of the placebo linearly 27 increased with training sessions (P<0.05). These results suggest that calcium propionate as an 28 65The effect of CaP as an appetite suppressant in poultry has been associated with low palatability, 66 gastrointestinal discomfort/malaise or the combination of both [17,23]. Independent of its 67 palatability, whether CaP causes a negative affective state post-ingestion remains unclear. 68The affective states of animals cannot be measured directly, but the study of animals' choices is 69 an indirect approach to assess their preferences [25]. For example, behavioural tests that looked at 70 the affective states and the preferences of broiler breeders include operant learning/response, state 71 dependent learning and conditioned place preference/avoidance [26][27][28][29][30][31]. Conditioned place 72 preference/avoid (CPP/CPA) tests are often used to analyse the possible positive (i.e., rewarding) 73 or negative (i.e., punishing) effects of pharmaceutical drugs or dietary additives [32]. During 74 CPP/CPA tests, animals are trained to associate given characteristics of its environment with 75 affective states induced by the treatment, and this environmental cue can become a conditioned 76 stimulus associated with the given affective state [32,33]. Once the condition is created, animals 77 are hypothesized to prefer the environment associated with the relative higher positive affective 78 state when they are tested in a T-maze [32,33]. Indeed, Phillips and Strojan [34] s...