Optimisation of the level of poultry by-product meal inclusion in pet treats using acceptability study and owner’s preference evaluation

Introduction

The increasing humanisation of companion animals has markedly transformed pet feeding practices, leading to a growing demand for nutrition-dense, functional and high-quality pet food products. Within this evolving landscape, pet treats have gained considerable importance in modern canine management, functioning not only as rewards and training aids but also as supplementary sources of nutrients. Consequently, the formulation of pet treats that combine nutritional adequacy with high sensory acceptability has become a key focus for the pet food industry. Rendered poultry by-product meal (PBM) represents a nutritionally valuable ingredient for pet food formulations, owing to its high protein content, balanced amino acid profile, mineral richness and cost-effectiveness. The utilisation of PBM also contributes to sustainable animal production by enabling the efficient valorisation of poultry processing byproducts. However, the nutritional and sensory quality of PBM may vary considerably depending on the nature of the raw materials and the rendering conditions employed. Such variability can influence the aroma, flavour and overall sensory characteristics of finished products, thereby affecting palatability and acceptance by dogs.

Palatability is a critical determinant of pet food success, as dogs rely predominantly on olfactory and gustatory cues during feed selection. Although higher inclusion levels of rendered animal by-products can enhance the nutritional profile of pet foods, excessive incorporation may intensify characteristic odours and flavours, potentially reducing voluntary intake despite improved nutrient density. In addition to animal response, owner perception plays a decisive role in product selection and market success. Attributes such as appearance, odour, texture and perceived naturalness strongly influence owner acceptance, purchase intent and brand loyalty. In this context, the optimisation of PBM inclusion levels is essential to achieve an appropriate balance between nutritional enrichment and sensory acceptability. Therefore, the present study was undertaken to determine the optimal level of PBM incorporation in the development of protein-rich, shelf-stable canine pet treats through systematic palatability evaluation in dogs, complemented by structured sensory preference assessment by pet owners.

Materials and Methods

Raw Materials and formulation

Rendered poultry by-product meal (PBM) containing 60 and 70% crude protein was procured from a local commercial supplier. The formulation also comprised fresh chicken meat, whole egg, millet flours (finger millet and pearl millet), sweet potato, selected vegetable powders, rendered poultry oil, flaxseed oil, bovine blood plasma, gelatin, a vitamin mineral premix and common salt, incorporated in proportions as detailed in Table 1. The level of PBM in the formulation was progressively increased by proportionate replacement of millet flours and sweet potato.

Procedure for Preparation of Pet Treats

The ingredients specified in the formulation (Table 1) were prepared and accurately weighed according to the prescribed levels. Initially, all dry ingredients, namely rendered poultry by-product meal, millet flour, powdered vegetables, common salt and vitamin mineral premix, were transferred into a planetary mixer (ITALYA Mixer, Model VFM10A, India) followed by the wet ingredients, including minced chicken meat, whole egg, vegetable oil, rendered poultry oil, flaxseed oil, bovine blood plasma and gelatin and blended until a homogeneous dough mixture was obtained. The prepared batter was then cold-extruded to form strands of approximately one cm in diameter and subjected to freezing for 30 min to facilitate handling and uniform shaping. The partially frozen extrudates were cut under hygienic conditions into uniform pieces measuring approximately one cm in diameter and 1.5 cm in height. The shaped pet bites were baked in a preheated hot air oven at 130 °C for 50 min, followed by tempering within the oven for an additional 10 min. After baking, the products were removed from the oven, allowed to cool to ambient temperature and aerobically packed in polyethylene/aluminium/polyamide (PE/Al/PA) laminated pouches. The pouches were sealed using a continuous band sealer (Sepack, Sevana, Cochin, India) and stored at ambient temperature.

Acceptability Test and Owner's Preference Evaluation

Based on preliminary evaluations, three formulations containing 70% crude protein Poultry By-Product Meal (PBM) were selected for preference testing: T1 (25% PBM), T2 (30% PBM) and T3 (35% PBM). The palatability and acceptability of these formulations were assessed using ten adult dogs maintained under uniform management conditions. Following the preference testing methodology described by Griffin, the study was conducted in four phases using standard paired comparison protocols. The first-choice preference, interest to eat and intake ratio were evaluated. Throughout the feeding trials, behavioural responses-including chewing patterns, tail wagging, vocalisation and lip licking-were recorded, along with any signs of digestive discomfort. Owner preference evaluation was performed using a five-point hedonic scale. Owners assessed the products based on colour and appearance, surface texture, shape consistency, perceived naturalness, odour, overall acceptability and purchase intent. Based on the combined outcomes of the dog palatability trials and owner preference scores, the formulation with the highest overall acceptability was selected as the standardised product. Consequently, the maximum PBM inclusion level was optimised to maintain high acceptability and owner preference without compromising product quality.

Results

Palatability and Acceptability

The palatability and acceptability of pet treats formulated with varying inclusion levels of poultry by-product meal (PBM) were evaluated using a structured scorecard comprising two complementary components. The first component involved owner-based sensory assessment, while the second consisted of direct behavioural observations of dogs during feeding. The evaluations were conducted on ten homogeneous dogs maintained under uniform managemental conditions and the resulting data, expressed as%, are presented in Table 4 and5. First-choice preference exhibited a pronounced treatment effect. Treatment T1 (25% PBM) recorded the highest proportion of high preference responses (42.5%), followed by T2 (22.5%) and T3 (17.5%). In contrast, low preference responses increased progressively with increasing PBM inclusion, with the highest proportion observed in T3 (70.0%), followed by T2 (40.0%) and T1 (27.5%). Interest to eat declined with increasing PBM inclusion levels. A higher proportion of dogs consumed T1 completely (65.0%) compared to T2 (50.0%) and T3 (45.0%). Partial consumption was comparable among treatments, whereas rejection rates were highest for T3 (27.5%), followed by T2 (25.0%) and T1 (15.0%). Comparative intake ratio analysis using the chi-square test revealed that T1 was significantly preferred over T2 (p < 0.01) and T3 (p < 0.05). However, no significant difference (p > 0.05) was observed between T2 and T3, indicating comparable acceptability at higher PBM inclusion levels. Behavioural observations indicated that six out of ten dogs exhibited normal chewing behaviour, while two displayed gulping behaviour. One dog partially rejected the treat and one dog completely rejected it. Among the nine dogs that accepted the product, only three exhibited signs of satiety following consumption, whereas six demonstrated continued interest and demand for additional portions. Dogs displayed positive palatability-associated behaviours, including tail wagging, pawing, vocalisation and lip licking during feeding. No adverse digestive responses such as loose stools, vomiting or flatulence were observed across treatments, indicating good digestive tolerance of the formulated pet treats irrespective of PBM inclusion level.

Owner Preference

Owner perception of the formulated pet treats was evaluated using a five-point hedonic scale ranging from very poor to excellent. The assessment encompassed colour and appearance, surface texture and shape consistency, perceived naturalness, odour, overall acceptability and purchase intent.

The results, expressed as%, are presented in Table 8. Colour and appearance received predominantly high (50.0-52.5%) and very high (47.5%) ratings across all treatments, with no responses recorded under the very low or low categories. This uniform trend indicates that variation in poultry by-product meal inclusion did not adversely influence the visual appeal of the pet treats. Surface texture and shape consistency were largely rated as moderate (47.5%) to high (45.0-47.5%) across treatments, reflecting acceptable firmness, cohesiveness and dimensional stability of the products. Only a small proportion of responses fell under the very high category, while no very low or low ratings were recorded. Perceived naturalness exhibited noticeable variation among treatments. Treatment T1 recorded a higher proportion of moderate (42.5%) and high (40.0%) ratings, whereas T3 showed a marked increase in low (47.5%) and very low (17.5%) responses, indicating a decline in perceived naturalness at higher PBM inclusion levels. Treatment T2 demonstrated an intermediate response pattern. Odour was predominantly rated as moderate (50.0-57.5%) across all formulations. However, T3 recorded a higher proportion of low ratings (20.0%) compared to T1 and T2, suggesting a perceptible change in aroma intensity with increased PBM incorporation. Overall acceptability was highest for T1, with 47.5% of responses classified under the high category. Treatment T2 was characterised by a predominance of moderate ratings (67.5%), while T3 exhibited a clear shift towards lower acceptance levels, with 27.5% and 10.0% of responses falling under the low and very low categories, respectively. A comparable trend was observed for purchase intent. The highest willingness to purchase was recorded for T1, with 50.0% of respondents indicating a high level of purchase intent. This willingness progressively declined in T2 and T3, concomitant with increasing PBM inclusion.

Discussion

Palatability and Acceptability

Palatability and acceptability assessments revealed a clear influence of poultry by-product meal inclusion level on canine feeding preference (Table 5, 6 and7). Treatment T1 (25% PBM) recorded the highest proportion of first-choice preference responses (42.5%), followed by T2 (22.5%) and T3 (17.5%). Conversely, low-preference responses increased markedly with higher PBM inclusion, reaching 70.0% in T3. These findings indicate a progressive decline in immediate acceptability as PBM concentration increased beyond 25%. A similar trend was observed in the 'interest to eat' parameter, where complete consumption was highest for T1 (65.0%) and declined for T2 (50.0%) and T3 (45.0%). Although partial consumption remained relatively comparable among treatments, rejection rates were highest for T3, suggesting that elevated PBM levels may negatively influence voluntary intake. Intake ratio analysis further substantiated these observations, demonstrating a statistically significant preference for T1 over both T2 (p < 0.01) and T3 (p < 0.05), while no significant difference was detected between T2 and T3, indicating comparable acceptability at higher PBM inclusion levels. These results corroborate earlier findings that first-choice and intake ratio tests are sensitive indicators of immediate palatability driven primarily by sensory cues such as aroma and flavour (Griffin, 2003) [5] . In dogs, olfactory perception plays a dominant role in food selection, often overriding gustatory inputs, with animal-derived odours acting as critical determinants of acceptance (Thombre, 2004) [10] . While poultry by-product meal enhances nutritional density, higher inclusion levels may intensify characteristic odours associated with rendered ingredients, potentially leading to reduced initial preference despite adequate nutrient composition (Oba et al., 2022) [7] . Behavioural observations during feeding further supported the palatability findings. The majority of dogs exhibited normal chewing behaviour, accompanied by positive palatabilityassociated responses such as tail wagging, lip licking, pawing and vocalisation. The absence of adverse digestive responses, including loose stools, vomiting or flatulence, across all treatments indicates satisfactory gastrointestinal tolerance and confirms that reduced preference at higher PBM levels was not related to post-ingestive discomfort. This observation aligns with the concept that palatability reflects pre-absorptive sensory perception rather than post-digestive physiological effects (NRC, 2006). Overall, while higher PBM inclusion enhanced protein and mineral density, palatability outcomes indicate that 25-30% PBM represents an optimal inclusion range for balancing nutritional enrichment with consumer-driven acceptability. These findings emphasise the importance of integrating sensory evaluation with nutritional optimisation during the formulation of functional pet treats.

Owner Preference

Owner-based sensory evaluation provides critical insight into the market acceptability of pet treats, as purchasing decisions are predominantly driven by human perception rather than animal response alone. In the present study, owner preference was assessed using a structured five-point hedonic scale encompassing visual, textural, olfactory and holistic acceptance parameters, thereby enabling a comprehensive appraisal of product appeal.

Colour and appearance received consistently high to very high ratings across all treatments, with no responses recorded under the very low or low categories. This uniform response indicates that variation in poultry by-product meal (PBM) inclusion up to 35% did not adversely affect the visual appeal of the pet treats. These findings are in agreement with earlier reports demonstrating that colour uniformity and surface appearance are among the primary cues influencing owner acceptance of dry pet foods (Di Donfrancesco et al., 2014) [2] . The instrumental colour values observed in the present study further corroborate these subjective assessments, confirming that PBM incorporation did not result in visually undesirable products. Surface texture and shape consistency were predominantly rated as moderate to high across all formulations, reflecting acceptable firmness, cohesiveness and dimensional stability of the baked treats. The absence of low or very low ratings indicates that the processing protocol ensured structural integrity irrespective of PBM inclusion level. Textural consistency is a key quality attribute in pet treats, as irregular shape or excessive friability is often associated with poor processing control and reduced consumer confidence (Tobie et al., 2015) [11] . In contrast, perceived naturalness exhibited a marked decline with increasing PBM incorporation. Treatment T1 received a higher proportion of moderate to high ratings, whereas T3 showed a substantial shift towards low and very low responses. This trend suggests that elevated inclusion of rendered byproducts may negatively influence owner perception of ingredient naturalness, despite their recognised nutritional value. Similar findings have been reported in studies examining owner attitudes towards animal by-products, wherein increased inclusion levels were associated with diminished perceptions of product wholesomeness and transparency (Dust et al., 2005) [4] . Odour evaluation further reflected this pattern, with T3 recording a higher proportion of low ratings compared to T1 and T2. Although odour was predominantly rated as moderate across all treatments, the increased frequency of unfavourable responses at higher PBM levels indicates that intensified aroma associated with rendered poultry ingredients may adversely affect owner acceptance. Odour perception is a critical determinant of purchase intent, as owners often associate strong or unfamiliar aromas with inferior quality or reduced freshness, irrespective of actual nutritional merit (Tobie et al., 2015) [11] . These combined effects were reflected in overall acceptability and purchase intent scores. Treatment T1 achieved the highest overall acceptability, with nearly half of the respondents rating it under the high category, whereas T2 was characterised by a predominance of moderate responses. In contrast, T3 exhibited a clear shift towards lower acceptance levels, accompanied by a marked reduction in purchase intent. This progressive decline in owner willingness to purchase with increasing PBM inclusion highlights the decisive role of human sensory perception in determining the commercial viability of pet treats. Overall, the present findings demonstrate that while higher PBM inclusion enhances nutritional density, owner preference is optimised at lower inclusion levels. A PBM inclusion rate of 25% provides the most favourable balance between visual appeal, perceived naturalness, odour acceptability and purchase intent, thereby supporting its selection as the optimal formulation from a consumer acceptance perspective. These results underscore the importance of harmonising nutritional optimisation with owner-driven sensory expectations in the development of functional pet treats.

Conclusion

The present study demonstrated that rendered poultry by-product meal can be effectively utilised in the formulation of protein-rich canine pet treats. However, palatability and overall acceptability declined progressively with PBM inclusion levels exceeding 25%. Based on combined canine preference, intake behaviour and owner sensory perception, a PBM inclusion level of 25% was identified as optimal. This level ensures enhanced nutritional value while maintaining superior palatability and consumer acceptance, thereby supporting its suitability for commercial pet treat formulations.

Acknowledgement

Acknowledgement:The authors gratefully acknowledge the facilities and support provided by the Department of Livestock Products Technology, College of Veterinary and Animal Sciences, Mannuthy, Thrissur.

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