Exploratory study of the effects of intra-uterine growth retardation and neonatal energy supplementation of low birth-weight piglets on their post-weaning cognitive abilities

Validating an updated protocol for the novel object recognition task in young pigs

The objective of this study was to validate equipment and procedures involved in implementing the novel object recognition (NOR) paradigm with young pigs. Two experiments were run with the intent of determining improvements to the original, high-throughput NOR paradigm design. The focus of these experiments was the impact of confounding factors on the main cognitive outcome, recognition index (RI). Experiment 1 utilized 13 pigs that all performed the NOR task following the original paradigm with the addition of 2 extra testing days. Results from this experiment indicated that one test day is sufficient for producing RI values that differ (p < 0.05) from chance performance, which was set at 0.50 given the use of two objects. Results also indicated that pigs may habituate to the task itself after 1 day of testing as RI values were not different (p > 0.05) from that of chance on test days 2 or 3. Experiment 2 utilized 13 male and 16 female pigs to determine sex differences in paradigm outcomes in addition to introducing home-cage enrichment. Results indicated sex differences in investigative behaviors despite both sexes producing RI values different from that of chance. The impact of home-cage enrichment was less discernable, but evidence suggests a lack of influence. Overall, the modifications to the NOR paradigm described herein reduced variability in the primary outcome, RI, and thereby improved sensitivity of the behavioral assay compared with the original paradigm.

Determining underlying influences of data variability in the novel object recognition paradigm as used with young pigs

The novel object recognition (NOR) paradigm is a cognitive test that has been used with many species to detect differences in ability. Various iterations of the paradigm have been implemented, making it difficult to compare results both within and across species. Interpretations of the results are equally diverse, threatening the integrity of the paradigm. These inconsistencies have prompted a deeper dive into the variability of the resultant data. For the purposes of this meta-analysis, data originated from 12 studies involving 367 pigs that were subjected to the same NOR paradigm beginning between postnatal days 21 and 24. The main cognitive measure from the NOR paradigm is recognition index (RI), which was the focus of most of the analyses in this meta-analysis. RI was chosen as the main outcome as it determines a pig's preference for novelty, an innate behavior of cognitively intact pigs. A histogram of RI values (range 0 to 1) showed a bimodal distribution skewed to the right, suggesting that the interpretation of positive performance on the task may need to be stricter. Correlational analyses proved that the number of investigations and investigation time with both the novel and familiar objects were the strongest predictors of resultant RI values. Objective data inclusion criteria were then considered to eliminate non-compliant pigs. Results indicated that requiring at least 5 s of investigation over a minimum of 3 investigations with the novel object reduced overall variability for RI with a concomitant increase in the mean. Further analyses showed that pigs preferred to spend more time with and interact more with the novel object across the entire testing trial, especially in the first minute. Together, these findings suggest that future interpretations of NOR should consider applying stricter statistical analyses as well as additional data processing, such as binning, with emphasis on novel object and familiar object investigation. Overall, modifications to the existing iterations of the NOR paradigm are necessary to improve paradigm reliability.

Cognitive tasks as measures of pig welfare: a systematic review

Cognitive approaches are increasingly used to assess animal welfare, but no systematic review has been conducted on pigs despite their cognitive capacities. Our aims were two-fold: first, to assess the popularity and heterogeneity of this approach by quantifying the different cognitive tasks used and welfare interventions studied. The second was to assess how often results from cognitive tasks supported treatment effects. The search yielded 36 studies that met our criteria. Eleven different cognitive tasks were applied (three most common: judgment bias, learned approach/aversion, and holeboard). Welfare interventions investigated were also diverse: the impact of 19 other different events/conditions/states were reported (most common: housing enrichment). We defined "supportive" as the observation of a significant difference between treatment groups consistent with an author's expectation or hypothesis. Supportive findings were reported in 44% of papers. Interventions yielded no significant difference in 33% of studies. In another 21% of reports, outcomes were mixed and a single study refuted the author's predictions. When considering specific cognitive tasks, authors' predictions of welfare differences were supported most often when using learned approach/aversion (55% of these studies). Similar supportive results were observed less commonly (40% each) when using judgment bias and holeboard tests. Analysis of additional concomitant measures of welfare (health, physiology or behavior) revealed that behavioral measures were most frequently supportive of author's expectations (41%) as well as often matching the actual outcomes of these cognitive tasks (47%). This systematic review highlights the growing popularity of cognitive tasks as measures of pig welfare. However, overall rates of supportive results, i.e., changes in performance on cognitive tasks due to welfare interventions, have been limited so far, even for the most employed task, judgment bias. The numerous different combinations of experimental paradigms and welfare interventions reported in the literature creates challenges for a critical meta-analysis of the field especially in evaluating the efficiency of specific cognitive tasks in assessing animal welfare. This work also highlights important knowledge gaps in the use of cognitive tasks that will require both further validation as well as novel innovation to ensure that their potential is fully realized in the measurement of pig welfare.

Subarachnoid hemorrhage in C57BL/6J mice increases motor stereotypies and compulsive-like behaviors

OBJECTIVE

Long-term behavioral, mood, and cognitive deficits affect over 30% of patients with subarachnoid hemorrhage (SAH). The aim of the present study was to examine the neurobehavioral outcomes following endovascular perforation induced SAH in mice.

METHODS

C57BL/6 J (B6) mice were exposed to endovascular perforation induced SAH or control surgery. Three weeks later, mice received a series of behavioral tests, e.g. motor function, stereotypy, learning, memory, behavioral flexibility, depression and anxiety. The immunohistologic experiment examined neuronalloss in the cortex following SAH.

RESULTS

SAH mice exhibited increased marble burying and nestlet shredding compared to that of control mice. Although SAH did not affect memory, learning or reversal learning,mice displayed greater overall object exploration in the novel object recognition test, as well as elevated perseveration during probabilistic reversal learning.In the forced swim and open field tests, SAH mice performed comparably to that of control mice. However, SAH mice exhibited an increased frequency in 'jumping' behavior in the open field test. Histological analyses revealed reduced neuron density in the parietal-entorhinal cortices of SAH mice on the injured side compared to that of control mice.

DISCUSSION

The findings suggest that parietal-entorhinal damage from SAH increases stereotyped motor behaviors and 'compulsive-like' behaviors without affecting cognition (learning and memory) or mood (anxiety and depression). This model can be used to better understand the neuropathophysiology following SAH that contributes to behavioral impairments in survivors with no gross sensory-motor deficits.