Modeling Risk Factors for Intraindividual Variability: A Mixed-Effects Beta-Binomial Model Applied to Cognitive Function in Older People in the English Longitudinal Study of Ageing.

Cognitive functioning in older age profoundly impacts quality of life and health. While most research on cognition in older age has focused on mean levels, intraindividual variability (IIV) around this may have risk factors and outcomes independent of the mean value. Investigating risk factors associated with IIV has typically involved deriving a summary statistic for each person from residual error around a fitted mean. However, this ignores uncertainty in the estimates, prohibits exploring associations with time-varying factors, and is biased by floor/ceiling effects. To address this, we propose a mixed-effects location scale beta-binomial model for estimating average probability and IIV in a word recall test in the English Longitudinal Study of Ageing. After adjusting for mean performance, an analysis of 9,873 individuals across 7 (mean = 3.4) waves (2002-2015) found IIV to be greater at older ages, with lower education, in females, with more difficulties in activities of daily living, in later birth cohorts, and when interviewers recorded issues potentially affecting test performance. Our study introduces a novel method for identifying groups with greater IIV in bounded discrete outcomes. Our findings have implications for daily functioning and care, and further work is needed to identify the impact for future health outcomes.

Joint Modeling of Individual Trajectories, Within-Individual Variability, and a Later Outcome: Systolic Blood Pressure Through Childhood and Left Ventricular Mass in Early Adulthood.

Within-individual variability of repeatedly measured exposures might predict later outcomes (e.g., blood pressure (BP) variability (BPV) is an independent cardiovascular risk factor above and beyond mean BP). Because 2-stage methods, known to introduce bias, are typically used to investigate such associations, we introduce a joint modeling approach, examining associations of mean BP and BPV across childhood with left ventricular mass (indexed to height; LVMI) in early adulthood with data (collected 1990-2011) from the UK Avon Longitudinal Study of Parents and Children cohort. Using multilevel models, we allowed BPV to vary between individuals (a "random effect") as well as to depend on covariates (allowing for heteroskedasticity). We further distinguished within-clinic variability ("measurement error") from visit-to-visit BPV. BPV was predicted to be greater at older ages, at higher body weights, and in female participants and was positively correlated with mean BP. BPV had a weak positive association with LVMI (10% increase in within-individual BP variance was predicted to increase LVMI by 0.21%, 95% credible interval: -0.23, 0.69), but this association became negative (-0.78%, 95% credible interval: -2.54, 0.22) once the effect of mean BP on LVMI was adjusted for. This joint modeling approach offers a flexible method of relating repeatedly measured exposures to later outcomes.

A two-year participatory intervention project with owners to reduce lameness and limb abnormalities in working horses in Jaipur, India.

BACKGROUND: Participatory methods are increasingly used in international human development, but scientific evaluation of their efficacy versus a control group is rare. Working horses support families in impoverished communities. Lameness and limb abnormalities are highly prevalent in these animals and a cause for welfare concern. We aimed to stimulate and evaluate improvements in lameness and limb abnormalities in horses whose owners took part in a 2-year participatory intervention project to reduce lameness (PI) versus a control group (C) in Jaipur, India. METHODOLOGY/PRINCIPAL FINDINGS: In total, 439 owners of 862 horses participated in the study. PI group owners from 21 communities were encouraged to meet regularly to discuss management and work practices influencing lameness and poor welfare and to track their own progress in improving these. Lameness examinations (41 parameters) were conducted at the start of the study (Baseline), and after 1 year and 2 years. Results were compared with control horses from a further 21 communities outside the intervention. Of the 149 horses assessed on all three occasions, PI horses showed significantly (P<0.05) greater improvement than C horses in 20 parameters, most notably overall lameness score, measures of sole pain and range of movement on limb flexion. Control horses showed slight but significantly greater improvements in four parameters, including frog quality in fore and hindlimbs. CONCLUSIONS/SIGNIFICANCE: This participatory intervention succeeded in improving lameness and some limb abnormalities in working horses, by encouraging changes in management and work practices which were feasible within owners' socioeconomic and environmental constraints. Demonstration of the potentially sustainable improvements achieved here should encourage further development of participatory intervention approaches to benefit humans and animals in other contexts.

Evaluation of changes in equine care and limb-related abnormalities in working horses in Jaipur, India, as part of a two year participatory intervention study.

BACKGROUND: Previous studies have found the prevalence of lameness in working horses to be 90-100%. Risk factors for lameness in this important equine population, together with risk-reduction strategies adopted by their owners, are poorly understood. The objective was to uncover risk factors for lameness and limb abnormalities in working horses, by associating clinical lameness examination findings on three occasions over two years with owner reported changes in equine management and work practices over this period. METHODOLOGY/PRINCIPAL FINDINGS: Twenty-one communities of horse owners in Jaipur, India, took part in a participatory intervention (PI) project aiming to reduce risk factors for poor welfare, particularly lameness and limb problems. Associations between quantitative measures of equine lameness/limb abnormalities and reported changes in management and work practices were compared with 21 control (C) communities of owners where no intervention had taken place. Key findings from 'complete cases', where the same horse stayed with the same owner for the whole study period (PI group = 73 owners of 83 horses, C group = 58 owners of 66 horses), were that more positive statements of change in equine management and work practices were made by PI group owners than C group owners. A mixed picture of potential risk factors emerged: some reported management improvements, for example reducing the weight of the load for cart animals, were associated with improved limbs and lameness, and others, such as making improvements in shoeing and increasing the age at which their animals started work, with negative outcomes. CONCLUSIONS/SIGNIFICANCE: This study illustrates the complexity and interacting nature of risk factors for lameness in working horses, and highlights the importance of longitudinal investigations that recognise and address this. PI group owners found the project useful and requested similar inputs in future. Our findings demonstrate the value of exploratory and participatory research methodology in the field of working horse welfare.

The place of experimental design and statistics in the 3Rs.

The 3Rs--replacement, reduction, and refinement--can be applied to any animal experiment by researchers and other bodies seeking to conduct those studies in as humane a manner as possible. Key to the success of this endeavor is an appreciation of the principles of good experimental design and analysis; these need to be considered in concert before any data is collected. Indeed, many of the principles central to helping achieve the objectives of the 3Rs-such as conducting valid, reliable, and efficient experiments; clearly and transparently reporting findings; and ensuring that an appreciation and understanding of animal welfare plays a central role in laboratory practice-are to the betterment of research per se.

Housing conditions affect rat responses to two types of ambiguity in a reward-reward discrimination cognitive bias task.

Decision-making under ambiguity in cognitive bias tasks is a promising new indicator of affective valence in animals. Rat studies support the hypothesis that animals in a negative affective state evaluate ambiguous cues negatively. Prior automated operant go/go judgement bias tasks have involved training rats that an auditory cue of one frequency predicts a Reward and a cue of a different frequency predicts a Punisher (RP task), and then measuring whether ambiguous cues of intermediate frequency are judged as predicting reward ('optimism') or punishment ('pessimism'). We investigated whether an automated Reward-Reward (RR) task yielded similar results to, and was faster to train than, RP tasks. We also introduced a new ambiguity test (simultaneous presentation of the two training cues) alongside the standard single ambiguous cue test. Half of the rats experienced an unpredictable housing treatment (UHT) designed to induce a negative state. Control rats were relatively 'pessimistic', whilst UHT rats were quicker, but no less accurate, in their responses in the RR test, and showed less anxiety-like behaviour in independent tests. A possible reason for these findings is that rats adapted to and were stimulated by UHT, whilst control rats in a predictable environment were more sensitive to novelty and change. Responses in the new ambiguity test correlated positively with those in single ambiguous cue tests, and may provide a measure of attention bias. The RR task was quicker to train than previous automated RP tasks. Together, they could be used to disentangle how reward and punishment processes underpin affect-induced cognitive biases.

Thermal nociceptive threshold testing detects altered sensory processing in broiler chickens with spontaneous lameness.

Lameness is common in commercially reared broiler chickens but relationships between lameness and pain (and thus bird welfare) have proved complex, partly because lameness is often partially confounded with factors such as bodyweight, sex and pathology. Thermal nociceptive threshold (TNT) testing explores the neural processing of noxious stimuli, and so can contribute to our understanding of pain. Using an acute model of experimentally induced articular pain, we recently demonstrated that TNT was reduced in lame broiler chickens, and was subsequently attenuated by administration of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). This study extended these findings to a large sample of commercial broilers. It examined factors affecting thermal threshold (Part 1) and the effect of an NSAID drug (meloxicam, 5 mg/kg) and of an opioid (butorphanol; 4 mg/kg) (Part 2). Spontaneously lame and matched non-lame birds (n=167) from commercial farms were exposed to ramped thermal stimulations via a probe attached to the lateral aspect of the tarsometatarsus. Baseline skin temperature and temperature at which a behavioural avoidance response occurred (threshold) were recorded. In Part 1 bird characteristics influencing threshold were modelled; In Part 2 the effect of subcutaneous administration of meloxicam or butorphanol was investigated. Unexpectedly, after accounting for other influences, lameness increased threshold significantly (Part 1). In Part 2, meloxicam affected threshold differentially: it increased further in lame birds and decreased in non-lame birds. No effect of butorphanol was detected. Baseline skin temperature was also consistently a significant predictor of threshold. Overall, lameness significantly influenced threshold after other bird characteristics were taken into account. This, and a differential effect of meloxicam on lame birds, suggests that nociceptive processing may be altered in lame birds, though mechanisms for this require further investigation.

Prevalence of risk factors for tail biting on commercial farms and intervention strategies.

A husbandry advisory tool (HAT) was devised to help pig producers and their advisors identify and minimise possible risk factors for tail biting in finishing pigs. The prevalence of 83 risk factors identified from the literature and expert opinion was recorded on 65 commercial pig farms in England between May 2007 and July 2009. Those considered most important were associated with atmosphere/environment, environmental enrichment, the provision of food/drink and animal health factors. Forty-six farms received advice on minimising these risks and, of these, 27 also received a financial incentive to encourage the uptake of advice. A reduction in risk factors was observed on 42/57 farms visited at the end of the study, with the greatest reduction occurring on the farms that had been incentivised. However, farms not receiving advice also had reduced risk factors associated with atmosphere/environment and stocking density over the course of the study. In conclusion, while some risk factors are structural and require substantial capital investment to change, a significant reduction in the risk of tail biting can be achieved on many farms through the systematic evaluation and modification of management practices.

Anxiety-induced cognitive bias in non-human animals.

As in humans, 'cognitive biases' in the way in which animals judge ambiguous stimuli may be influenced by emotional state and hence a valuable new indicator of animal emotion. There is increasing evidence that animals experiencing different emotional states following exposure to long-term environmental manipulations show contrasting biases in their judgement of ambiguous stimuli. However, the specific type of induced emotional state is usually unknown. We investigated whether a short-term manipulation of emotional state has a similar effect on cognitive bias, using changes in light intensity; a treatment specifically related to anxiety-induction. Twenty-four male rats were trained to discriminate between two different locations, in either high ('H') or low ('L') light levels. One location was rewarded with palatable food and the other with aversive food. Once the rats had shown spatial discrimination, by running significantly faster to the rewarded location, they were tested with three ambiguous locations intermediate between the rewarded and aversive locations, and their latency to approach each location recorded. Half the rats were tested in the same light levels as during training, the remainder were switched. Rats switched from high to low light levels (putatively the least negative emotional manipulation) ran significantly faster to all three ambiguous probes than those rats switched from low to high light levels (putatively the most negative manipulation). This suggests that the judgement bias technique might be useful as an indicator of short-term changes in anxiety for non-human animals.

Sensitivity to reward loss as an indicator of animal emotion and welfare.

The scientific study of animal emotion is an important emerging discipline in subjects ranging from neuroscience to animal welfare research. In the absence of direct measures of conscious emotion, indirect behavioural and physiological measures are used. However, these may have significant limitations (e.g. indicating emotional arousal but not valence (positivity versus negativity)). A new approach, taking its impetus from human studies, proposes that biases in information processing, and underlying mechanisms relating to the evaluation of reward gains and losses, may reliably reflect emotional valence in animals. In general, people are more sensitive to reward losses than gains, but people in a negative affective state (e.g. depression) are particularly sensitive to losses. This may underlie broader findings such as an enhanced attention to, and memory of, negative events in depressed individuals. Here we show that rats in unenriched housing, who typically exhibit indicators of poorer welfare and a more negative affective state than those in enriched housing, display a prolonged response to a decrease in anticipated food reward, indicating enhanced sensitivity to reward loss. Sensitivity to reward reduction may thus be a valuable new indicator of animal emotion and welfare.