Behaviour directed towards inaccessible food predicts consumption—A novel way of assessing food preference

Insights to Study, Understand and Manage Extruded Dry Pet Food Palatability

Pet food production is a fast-growing industry. While extruded dry pet food is the favored pet food due to its convenience of use, it may have poorer palatability than other pet foods such as wet pet foods. However, palatability plays a pivotal role in meeting nutritional requirements or providing therapeutic benefits in cats and dogs, as it ensures food acceptance. Thus, both academics and manufacturers conduct routine palatability tests to assess acceptance and preference of products among pets, alongside sensory analyses involving human panels. Palatability is greatly influenced by species-specific and environmental factors in cats and dogs. The review will hence present the current knowledge on palatability assessment and animal food perception; it will then aim to explore strategies for effectively managing palatability in dry pet food by examining the impact of key ingredients and process parameters on the finished product's palatability. Moreover, the demands and needs for sustainable and healthier products as well as supply constraints present novel challenges and opportunities for academics and manufacturers.

Owner-implemented paired-stimulus food preference assessments for companion dogs

Behavioral interventions for animals typically require the inclusion of programmed reinforcers. Although pet owners and human caregivers can often identify items that the animal will consume, preference assessments can more accurately determine relative preference rankings between various stimuli, which is important given that higher preferred items tend to function as more effective reinforcers than lower preferred items. Preference assessments have been developed to identify rankings for a variety of stimuli across species, including the domesticated dog (Canis lupus familiaris). However, previous preference assessments for dogs were developed for laboratory use and could be challenging for dog owners to perform alone. The purpose of this study was to modify existing dog preference assessment methods to produce a valid and feasible preference assessment for dog owners. Results suggest that the preference assessment identified preference rankings for individual dogs. Owners were able to implement the protocol with high integrity and found the protocol acceptable.

How Dog Behavior Influences Pet Owner's Perceptions of Dog Preference for Dental Chews

American pet owners spend billions of dollars on food and treats so it is important to understand what products they want and what they think their dog would enjoy. This study analyzed video recordings of dogs engaging in dental chews in their home environment and compared the observed appetitive behaviors to owner preference and owner-reported dog preference. Overall, appetitive behavior differed significantly between some dental chews. Owner preference for the chews correlated significantly with dog appetitive behavior, but the effect was small (r (702) = 0.22, p = 0.001), whereas owner-reported dog preference correlated significantly with dog appetitive behavior and showed a moderate effect size (r (702) = 0.43, p = 0.001)-similar in magnitude to findings when parents are asked to report on their children's behavior. By merging objective behavioral observation of owner-recorded videos with their survey responses, we were able to preliminarily parse out what factors owners may use to assess preference and encourage the future use of in-home video recordings to better understand dog and owner engagement and interaction with pet products.

Sensory attributes, dog preference ranking, and oxidation rate evaluation of sorghum-based baked treats supplemented with soluble animal proteins

Treats are offered to dogs to reinforce the animal-owner bond and as rewards. Wheat, which contains gluten (gliadin and glutenin proteins), is often used in treats. The US is a leading producer of sorghum which might be an alternative; however, it does not have functional properties to form viscoelastic doughs, because is mainly composed of kafirin protein. Therefore, the objectives of this study were to determine the effects of supplementing soluble animal proteins in whole sorghum rotary molded baked dog treats on dog preference, sensory attributes, and oxidation rate. The treats were produced in triplicate in a 2x4 + 1 augmented factorial arrangement of treatments. Two whole sorghum flours (WWS and WRS), four protein sources [none (NC), spray-dried plasma (SDP), egg protein (EP), and gelatin (GL)], and a positive control with wheat (WWF-GTN) were evaluated. A preference ranking test with twelve dogs was performed. Additionally, five trained panelists scored the intensity of appearance, aroma, flavor, texture/mouthfeel, and aftertaste attributes. Finally, the treats were stored at 30°C and 60% RH, and hexanal concentrations were measured on days 0, 28, 56, and 112. The data was analyzed using the statistical software SAS for the animal and oxidation rate evaluations with significance considered at P<0.05. The descriptive sensory evaluation data was analyzed using multivariate analysis (XLSTAT). The dogs did not detect differences among WWF-GTN, WWS, or WRS treats when evaluated together. However, the WWF-GTN, WWS-SDP and WWS-EP treatments were preferred among the white sorghum treatments. The EP treatments led to some consumption difficulties by dogs because of their hard texture. The panelists reported a high degree of variation in the appearance and texture across treatments. The WRS and WWS treats with SDP or EP were darker, while NC treats had more surface cracks. Initial crispness, hardness, and fracturability were higher in EP treatments compared to all other sorghum treatments. The predominant flavor and aftertaste identified were "grainy." The hexanal values for all treats were <1.0 mg/kg except for the EP treatments that had higher values (2.0-19.3 mg/kg) across the shelf-life test. This work indicated that the replacement of WWF-GTN by WWS and WRS, along with soluble animal proteins like SDP or GL would produce comparable preference by dogs, oxidation rates, product aromatics, flavor, aftertaste attributes, and, at a lower degree, product texture.

Investigating food preference in zoo-housed meerkats

Understanding food preference among animals in human care can support improvements to welfare through training and day-to-day care (e.g., diet management). Little has been published about food preference in zoo-housed meerkats. Assessing meerkat food preference would be useful, not only for the welfare of that species, but also for developing approaches to assessing food preference in other group-housed, social species. The specific aim of this study was to quantify food preference within the meerkat mob at Wellington Zoo. We developed a simple, cost-effective method for characterizing the food preference hierarchy in meerkats by presenting pairs of foods to the mob as a group. We observed stable preference with the hierarchy for pups closely resembling that for adults. This study demonstrated that it is possible to assess food preference and identify a food preference hierarchy for a group of animals from a social species where it was neither practical nor appropriate to assess individuals' preferences separately.

Vegan versus meat-based pet foods: Owner-reported palatability behaviours and implications for canine and feline welfare

Consumer suspicion of conventional pet foods, along with perceived health benefits of alternative diets, are fuelling development of the latter. These include raw meat diets, in vitro meat products, and diets based on novel protein sources such as terrestrial and marine plants, insects, yeast and fungi. However, some claim vegan diets may be less palatable, or may compromise animal welfare. We surveyed 4,060 dog or cat guardians to determine the importance to them of pet food palatability, and the degree to which their animals displayed specific behavioural indicators of palatability at meal times. Guardians were asked to choose one dog or cat that had been within their household for at least one year, and not on a prescription or therapeutic diet. Of 3,976 respondents who played some role in pet diet decision-making, palatability was the third most important among 12 factors cited as important when choosing pet diets. For 1,585 respondents feeding conventional or raw meat diets, who stated they would realistically consider alternative diets, palatability was the fourth most important among 14 desired attributes. For the 2,308 dogs included, reported observations of 10 behavioural indicators of palatability at meal times reliably indicated significant effects of increased reports of appetitive behaviour by dogs on a raw meat diet, as opposed to a conventional diet. There was no consistent evidence of a difference between vegan diets and either the conventional or raw meat diets. For the 1,135 cats included, reported observations of 15 behavioural indicators indicated that diet made little difference to food-oriented behaviour. Based on these owner-reported behaviours, our results indicate that vegan pet foods are generally at least as palatable to dogs and cats as conventional meat or raw meat diets, and do not compromise their welfare, when other welfare determinants, such as nutritional requirements, are adequately provided.

Assessing effects of dietary and milking frequency changes and injection of cabergoline during dry-off on hunger in dairy cows using 2 feed-thwarting tests

We investigated the single and combined effects of 2 feeding levels (normal lactation diet vs. energy-reduced diet, both fed for ad libitum intake) and 2 daily milking frequencies (twice vs. once) during 1 wk before the dry-off day (d 0), as well as an intramuscular injection of either a dopamine agonist (cabergoline; Velactis, Ceva Santé Animale; labeled for use only with abrupt dry-off, e.g., no reduction in feeding level or milking frequency before the last milking) or saline after the last milking on d 0 on the feeding motivation of clinically healthy, loose-housed, pregnant, lactating Holstein cows. From d 0, all cows were fed the same dry-cow diet for ad libitum intake. Cows were subjected to 2 feed-thwarting tests, a test in the home pen using their diets (test A: d -6, -1, and 1; during 35 min when the feed bins were filled, but locked) and another test carried out in an adjacent pen in which access to concentrate provided in a familiar plastic box was blocked by a wire-mesh lid (test B: d -5 and 2). In test A, we recorded how often cows attempted to feed per 35 min, whether cows vocalized during the 35-min period, and latency to feed within 300 s after feed bins were unlocked. In test B, we recorded latency to approach either of 2 familiar boxes (the wire-mesh box and an identical open box with a small portion of concentrate) within 600 s and how often cows directed behaviors toward the wire-mesh box (number of occurences/5 min). On d -6 (test A), no clear differences in feeding motivation among treatments were found. On d -5 and -1, cows fed the energy-reduced diet displayed a higher probability of vocalizing (test A), were more than 50% quicker to feed (test A), were approximately 5× quicker to approach a box (test B), and directed 60% more behavior toward the wire-mesh box (test B) than cows fed the normal diet. Moreover, cows fed the energy-reduced diet attempted to feed approximately 75% more on d -1 compared with d -6 (test A). On d 2 (test B), cows previously fed the normal diet directed 40% more behavior toward the wire-mesh box than cows previously fed the energy-reduced diet. Reducing feeding level, either before or on the dry-off day, resulted in consistently increased feeding motivation, interpreted as a sign of hunger. No clear effects of change in milking frequency, singly or combined with reduced diet energy density, on feeding motivation were found before d 0. Whereas, on d 2, cows previously milked twice daily were quicker to approach a box than cows previously milked once daily. Cows injected with cabergoline attempted to feed more, but showed lower probability of vocalizing compared with saline-injected cows (d 1; test A), irrespective of treatment before d 0. The effects of cabergoline on feeding motivation are not easily interpreted and warrant further investigation. From a hunger perspective, reducing milking frequency rather than diet energy density seems to be a less negative management to reduce milk production before dry-off.

Behavioural responses to unexpected changes in reward quality

Successive negative contrast (SNC) effects are changes in anticipatory or consummatory behaviour when animals unexpectedly receive a lower value reward than they have received previously. SNC effects are often assumed to reflect frustration and appear to be influenced by background affective state. However, alternative explanations of SNC, such as the functional-search hypothesis, do not necessarily imply an aversive affective state. We tested 18 dogs in a SNC paradigm using a patch foraging task. Dogs were tested in two conditions, once with the low value reward in all of five trials (unshifted) and once when reward value was altered between high and low (shifted). Following a reward downshift, subjects showed a SNC effect by switching significantly more often between patches compared to the unshifted condition. However, approach latency, foraging time and quantity consumed did not differ between conditions, suggesting non-affective functional search behaviour rather than frustration. There was no relationship between strength of SNC and anxiety-related behaviours as measured in a novel object test and a personality questionnaire (C-BARQ). However, associations with the C-BARQ scores for Trainability and Stranger directed aggression suggest a possible link with behavioural flexibility and coping style. While reward quality clearly affects incentive motivation, the relationship between SNC, frustration and background affective state requires further exploration.

Incentive motivation in pet dogs - preference for constant vs varied food rewards

Recently, there has been a move towards positive reinforcement using food rewards in animal training. By definition, rewards function as reinforcers if they increase or maintain the frequency of behaviour that they follow. However, in operant conditioning tasks animals frequently show systematic changes in performance - in particular a reduction in responding over time. One suggested strategy to avoid such performance decrements is to provide a variety of food rewards, rather than the same food reward in all trials. The enhancement of appetitive behaviour and consumption by reward variation is referred to as 'variety effect'. We investigated whether dogs preferred a variable or a constant food reward in a concurrent two-choice test. Of 16 dogs, six subjects showed a significant preference for the varied food reward and six for the constant food reward, while four dogs exhibited no significant preference for either option. At the group level, there was a significant effect of block: preference for the varied food reward increased across six blocks of ten trials each. Thus, although some individuals may prefer a single, favourite food reward in the short term, introducing variation in reward types may maintain dogs' motivation in operant tasks over a longer time period.

Development and validation of the Canine Reward Responsiveness Scale -Examining individual differences in reward responsiveness of the domestic dog

Although there is ample data indicating that reward processing plays an important role in human psychopathologies and pharmaco- and psychotherapy treatment response, the corresponding animal-model research needs to be extended to models whose motivational and social dispositions are better generalizable than those of the traditional models. Accordingly, our aim was to develop and assess the reliability and validity of an owner-report rating scale of reward responsiveness in domestic dogs (N = 2149) and then to examine individual differences in reward responsiveness. Responsiveness was categorisable by reward type (ball/toy and food) and exhibited individual variability manifesting in age- and breed-related differences. Rating scale scores were associated with behavioural observation of reward processing, indicating evidence of convergent validity. Ball/toy and food reward responsiveness were associated with owner-rated hyperactivity-impulsivity‚ inattention and with differences in training, indicating evidence of concurrent validity. Extreme (vs. average) reward responsiveness was also predicted by dogs’ hyperactivity-impulsivity and inattention‚ and extreme responsiveness was associated with increased likelihood of physical health and/or social problems. These findings are informative with regard to the dog as an animal model for various human behavioural and cognitive functions‚ and also for the dog in its own right as they are relevant to training and welfare.

Canine Food Preference Assessment of Animal and Vegetable Ingredient-Based Diets Using Single-Pan Tests and Behavioral Observation

Knowledge of canine food selection is critical for both the pet food industry and dog owners, since owners want quality foods that are palatable, while fulfilling their pet's nutritional requirements. There are two common methods for assessing canine food preference: the two-pan test and the one-pan test. Neither test fully accounts for the complexity of the canine feeding experience nor do they provide applicable representations of canine feeding behavior in the home. The objectives of this study were to (1) determine whether dogs display a preference for animal ingredient-based diets when compared with vegetable ingredient-based diets and (2) examine whether dogs experience neophobia when presented with a novel diet. Eight adult Beagles (average age = 24 months, weighing 8-12 kg) were individually fed each of four novel diets in a 4 × 4 replicated Latin square design, with 10-d treatment periods and four dietary treatments. Data were analyzed using a mixed model with repeated measures and significance was declared when p < 0.05. The diets were: animal and vegetable ingredient-based diets, and animal- and vegetable-based ingredients diluted with anhydrous α-d-glucose. The diluted diets were used for a larger study to determine true mineral digestibility. Dogs were fed twice per day (0800 and 1300 h). Behavioral observations were made by video on the first, and last 2 days of each 10-day treatment period of both a.m. and p.m. feedings. Time to consume feed, distraction, hesitation, level of anticipation pre-consumption, and interest post-consumption were recorded. Dogs experienced initial disruptive (neophobic) effects of a novel diet. Neophobia was demonstrated by a decreased (slower) rate of consumption, increased distraction during consumption of the diet, and increased hesitation on the first day of each new diet (p < 0.05). The level of interest post-consumption was highest when dogs consumed the animal-based ingredients diet (p < 0.05). This study presents insights into canine food preference assessment methods that may more accurately represent the dog owner's experience. Further research is required to determine the minimum length of time necessary to eliminate neophobia to food. In addition, future research should also aim to establish whether interest post-consumption is due primarily to food preference or acute satiety.

Food and Food-Odor Preferences in Dogs: A Pilot Study

Evaluation of food palatability and preference is of great importance to the pet food industry. One common technique for evaluating palatability is a 2-bowl test in which 2 products are offered simultaneously and food consumption is measured. This yields clear results with dogs trained to routinely conduct such comparisons, but it is less clear how this extends to untrained pet dogs. In addition, prior research indicates that olfaction is important in food preference, but methods for evaluating odor preference in canines are currently lacking. In this study, we developed a modified 2-bowl test for evaluation of food preferences in pet dogs with minimal training, and an olfactometer technique for the evaluation of odor preferences. In our 2-bowl procedure, we observed clear preferences among 4 commercial food products in 6 pet dogs. Across repeated testing, preferences strengthened, but the first evaluation accurately estimated the direction and significance of preference. In addition, dogs typically (89% of the time) consumed more of the food they chose first, suggesting they did not need to taste each food to choose. Our odor preference olfactometer assessment, however, did not reveal odor preferences other than that dogs preferred to sniff a food odor over clean air. Further work will be needed to identify methods of measuring odor preferences amongst food odors for dogs, but the modified 2-bowl test shows promise for further testing in pet dogs.