van den Berg, M., Giagos, V., Lee, C. et al. 2016. Acceptance of novel food by horses: The influence of food cues and nutrient composition. Applied Animal Behaviour Science 183, 59-67.

Compared to ruminants little is known about how horses modulate food intake and learn about flavour-to-post-ingestive consequences. While it has been suggested that due to hindgut fermentation horses' foraging preferences may be largely influenced by sensory input (e.g. volatiles), it has been established that horses are able to differentiate and select familiar foods (e.g. concentrates and hay) based on nutritional content. Yet it remains unclear how this translates to the acceptance of nutritious novel foods (NF). Therefore, the influence of food cues and nutrient composition on NF acceptance were examined in two experiments using 11 adult mares. In experiment 1, we investigated the influence of a familiar odour (FO) on the acceptance of a nutritious NF and in experiment 2, we determined if horses have the ability to select nutritious NF based on the nutritional content, regardless of sensory preferences. In experiment 1 horses received identical NF in a two-choice test with one of the choices being masked with a FO over a 9-day period. In experiment 2 horses were offered a high or low protein option of an otherwise identical NF in a two-choice test in which the NFs were paired with two unfamiliar flavours (odours). The two-choice test lasted for 14days and the flavour-protein pairing was switched after 7days. NF intakes were recorded over a 10min test period on each test day and analysed using Bayesian hierarchical models. The results of experiment 1 indicate that a FO had a strong positive influence on the NF intake for the first 5days (90-100% of total consumption and strong evidence for non-zero temporal effects (Bayes factor B12=110)). This was followed by a more even distribution of intake for the remaining period. In experiment 2 horses had a greater intake of high protein NF regardless of the flavour on days 4, 6 and 7 (80-87% of total consumption) and this continued after the switch over (Day 9-14; 57-81% of total consumption). However, 4 out of 11 horses showed neophobia throughout the testing period, which could have been associated with the novel odours as horses scanned the buckets with little to no sampling. The results suggest that pre-ingestive cues (e.g. smell, taste) of foods play an important role in diet selection and that a FO can increase the acceptance of NF. This new knowledge could be applied by the horse industry to encourage the consumption of new food or forages by horses.