The effect of feeding enrichment in the milk-feeding stage on the cognition of dairy calves in a T-maze

In many species, environmental complexity is known to affect cognitive development, yet it is common to house dairy calves individually in restrictive environments. The hypothesis of this study was that providing calves with simple nutritional enrichments would improve their success in a cognitive task and reduce reactivity to novel stimuli. Individually-housed Holstein heifer calves were assigned at birth to conventional management (C; n =10), with access to milk (6 L/d) via bucket and grain concentrate, or enriched feeding (E; n-10), with access to milk via teat to allow natural suckling, and chopped hay alongside concentrate. At week 5 of age, calves were tested in a T-maze with a reward (0.2 L milk; provided according to familiar delivery method) placed in one arm to assess initial spatial learning, reversal learning where the reward location was changed to the opposite arm, and response to an intramaze change (novel object, a colored ball, was placed in the maze between the start position and reward). Calves received 5 sessions/d for 5 days or until criteria (moving directly to correct side in 3 consecutive sessions) was reached for initial and reversal learning. Time to complete the test, movement in maze, kicks, and non-nutritive licking/sniffing were recorded from video. In the initial learning stage, the number of sessions required to meet the learning criteria was similar between calves (P = 0.12). However, E calves took longer to complete the task in early sessions (treatment by session interaction; P = 0.02), due to increased time spent on the correct side of maze before obtaining the reward (26.72 vs. 7.48 s; SE = 3.4; P = 0.005). In the reversal learning stage, there was no overall difference in the number of sessions to meet the learning criteria (P = 0.20), but E calves completed the task faster (19.84 vs 27.22s; SE = 2.10; P = 0.03), and C calves spent 1.5 x longer on the incorrect side of the maze than E calves (P = 0.04), suggesting that C calves struggled to relearn the task. In both initial and reversal learning, C calves kicked more frequently (P < 0.04). During the novel object session, E calves found the reward faster (6.11 vs 20.6s; SE = 4.06; P = 0.01), whereas C calves spent longer in the middle of the maze where the novel object was located (2.08 vs 13.4s; SE = 5.33; P = 0.04). These results suggest that providing simple feeding enrichments during the milk feeding stage may alter calf cognition and influence responses to environmental changes. (C) 2016 Elsevier B.V. All rights reserved.