Learning and memory in maternally-reared and maternally-deprived pigs (Sus scrofa)

Mian, Riana (2007) Learning and memory in maternally-reared and maternally-deprived pigs (Sus scrofa). Masters thesis, Memorial University of Newfoundland.

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Abstract

Four sibling groups, each consisting of three Yucatan miniature pigs (Sus scrofa), were tested on the effects of rearing condition on learning and memory. Within each group of siblings, one piglet was sow-reared (SR), one piglet was a maternally-deprived runt (MD runt), and one piglet was a maternally-deprived large littermate (MD large). In Experiments 1 and 2, the pigs were trained to open tray lids and to shuttle from the entrance of the training room to the first pen and open a tray lid. All twelve pigs were able to learn both tasks. The SR pigs had longer latencies than the MD runt and MD large pigs in the shuttle task. These longer latencies in SR pigs may be explained by this group being more predisposed than MD pigs to explore their environment. Experiment 3 examined whether the MD and SR differed in their performance on discrimination and reversal tasks and whether experiencing a context change would facilitate reversal learning. There was no difference between the three rearing groups on these tasks. The pigs that experienced a context change learned a reversal in fewer errors to criterion than those that remained in the same context. This finding supports the hypothesis that context change serves as a conditional cue in reversal learning. Experiment 4 tested pigs' memory for the tray they visited less recently. Four pigs were exposed to four different trays with particular odors and locations in sequence. The pigs were then given a choice between the first and last items in the sequence. All four pigs chose correctly at an above chance level. The results suggest that pigs are sensitive to relative recency. These findings may lead to further episodic-like memory tests with pigs.

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