Some like it varied: Individual differences in preference for feed variety in dairy heifers

Motivation to explore is believed to be widespread among animals, but exploratory behaviour varies within populations. Offering variety in feed is one simple way of allowing intensively housed dairy cattle to express exploratory foraging behaviour. Individuals' exploration of different feed types, as with other new stimuli, likely reflects a balance between exploratory motivation and fear of novelty. We tested the degree to which Holstein heifers (n = 10) preferred variety in feed vs. a constant, high quality mixed ration, by first providing varying types of forages and then varying flavours of mixed feed. We also investigated individual differences in exploratory behaviour by measuring switching between feed bins. Individual consistency in preferences was assessed between tests, and longer-term consistency was evaluated by comparing these results with behaviour in novel object and novel feed tests before weaning. On average, the heifers preferred the constant, familiar feed (spending on average just 20% of their time at varied feed bins), but this preference varied among individuals (from 0 to 46% of time eating in the forage trial, and 0-93% in the flavour trial). Preference for varied forages correlated positively with intake of novel feed as calves (rs = 0.72, n = 9). Preference for varied flavours showed a negative correlation with latency to approach a novel object (rs = −0.65). It thus appears that preference for variety and exploratory foraging behaviour reflect consistent personality traits. These results suggest that offering novel feeds on a rotating schedule as a supplement to the regular diet may be an effective form of enrichment for at least some individuals within a herd.