Evaluation of grooming behaviour and apparent digestibility method in cats

Abstract

Objectives

This experiment was conducted to evaluate the behavioural time budget for grooming and grooming patterns for shorthair and longhair cats, and to assess the effect of grooming behaviour on apparent digestibility of nutrients in domestic cats (Felis catus) by comparing hair-included faeces and hair-removed faeces.

Methods

A total of 10 adult domestic cats, with a mean ± SD body weight of 4.3 ± 0.89 kg and a mean ± SD age of 3.5 ± 1.38 years, were used for behavioural observation. Cats were housed individually in stainless steel cages at the animal hospital. The cats’ behaviour was recorded on a webcam videotaping system for one 24 h period; then, faecal samples were collected and analysed to measure apparent digestibility.

Results

There was no significant difference between longhair and shorthair cats in behavioural time budget for grooming and grooming patterns. The apparent digestibility of dry matter, crude protein, crude ash, acid detergent fibre (ADF) and neutral detergent fibre (NDF) of hair-removed faeces was significantly higher than that of hair-included faeces: about 6% (P <0.01), 7% (P <0.01), 14% (P <0.01), 12% (P = 0.01) and 10% (P <0.01), respectively.

Conclusions and relevance

There was no difference in grooming patterns between longhair cats and shorthair cats. Also, the digestibility of dry matter, crude protein, crude ash, ADF and NDF has been underestimated by approximately 6%, 7%, 14%, 12%, and 10%, respectively, when they have been calculated using the conventional digestibility method for domestic cats.

Introduction

Small felids, including domestic cats, are known for frequent grooming. ¹ Cats engage in paw licking and face washing, as well as licking the pelage. As cats typically draw the keratinous cornified papillae of the tongue over the surface of the pelage, they ingest a large amount of hair while licking.^1,2

Grooming serves several purposes, such as removal of lost hair to keep the coat free from mats and dander to maintain healthy skin. Grooming removes ectoparasites,^3,4 and it also removes dirt and stale oil, thus maintaining the insulating capacity of the pelage and temperature control. ¹

A cat can spend approximately 25–30% of its time grooming.^5,6 Some cats have been observed to spend up to one-third of their time awake grooming, ⁷ and domestic cats spend about 50% of their time budget sleeping and resting. ¹ Oral and scratch grooming accounted for 4% and 0.1%, respectively, of the overall time budget, or 8% and 0.2%, respectively, of non-sleeping resting time when grooming was possible. The greatest amount of oral grooming was carried out around the head in the form of face washing (31%), followed by licking of the hindlimb (21%), sides/back (13%), neck/chest (11%), anogenital region (10%), abdomen (9%) and tail (5%). ¹

The aim of the current study was to use simultaneous measurements of quantitative and qualitative behaviour to provide a 24 h time budget for grooming in shorthair cats and longhair cats, and to assess the effect of grooming behaviour on apparent digestibility in domestic cats (Felis catus) by examining the time budget for grooming in both shorthair and longhair cats and comparing the apparent digestibility of nutrients in domestic cats.

Materials and methods

Ethics

All animal procedures were approved by the Institutional Animal Care and Use Committee of Seoul National University (SNUIACUC-160712-22) before the animal experiment. The present study was conducted according to guidelines provided by SNUIACUC.

Animals

Ten adult domestic cats (F catus; five longhair cats and five shorthair cats; mean ± SD age 3.5 ± 1.38 years; mean ± SD body weight 4.3 ± 0.89 kg; five males and five females, all of which were neutered) were analysed for their behaviour. An additional four cats were included for the digestibility trial, resulting in a total of 14 cats (six longhair and eight shorthair; mean ± SD age of 3.3 ± 1.38 years and a mean ± SD body weight of 4.5 ± 1.21 kg; seven females and seven males, all of which were neutered). Good health status was confirmed prior to beginning the study by veterinarians working in Irion Animal Hospital (Seoul, Republic of Korea).

Housing and management

Cats were housed individually in stainless steel cages (0.77 × 0.51 × 0.63 m; Figure 1) at Irion Animal Hospital at a constant temperature (22–23°C). Because videotaping was used to record behaviour for detailed analysis, it was necessary for each cat to be placed alone in an observation cage. Within each cage, there was a shelf (0.51 × 0.29 m) elevated (0.3 m) off the floor, a litter box (0.33 × 0.44 × 0.16 m) and water dishes secured to the cage door. Starting at 06:00 h, 14 h of fluorescent light were provided followed by 10 h of darkness, supplemented with infrared lighting from the recording webcam. The subjects were in visual, auditory and olfactory contact with the other cats of the colony.

Figure 1.

Experimental cage (size 77 × 51 × 63 cm)

All cats remained healthy throughout the study, with no signs of ectoparasitism. The cats were individually offered calculated amounts of dry extruded diet (chicken based grain-free commercial feed, provided by Daehan Feed, Republic of Korea; Table 1). The amount was defined according to the energy requirements for adult cat maintenance, estimated as ME = 100 × BW^0.67, where ME refers to metabolisable energy and BW is body weight. ⁸ Food was provided twice daily (at 09:00 h and 16:00 h). Water was provided ad libitum. Litter boxes were cleaned between 08:00 h and 09:00 h, and between 15:00 h and 16:00 h.

Table 1.

Analysed nutrition values of experimental diet (provided by Daehan Feed)

Criteria	Experimental diet (%)
Moisture	6.47
Crude protein	33.01
Crude ash	7.56
Crude fat	15.40
Calcium	1.33
Total phosphorus	0.89
Crude fibre	3.59
Acid detergent fibre	11.52
Neutral detergent fibre	33.98

Feed ingredients: fresh salmon, fresh chicken, chicken meat powder, tapioca, potato powder, cellulose powder, linseed, chicken fat, dried yeast, salt, chicken hydrolysate powder, taurine, vitamin C, vitamin E, methionine, lysine, choline chloride, organic mineral, vitamin premix, mineral premix, yucca extract, grape seed extract (natural antioxidant), probiotics, enzymes, FOS (probiotics), herbs

Continuous quantitative behavioural observation

The cats’ behaviour was recorded on a webcam videotaping system for one 24 h period following an initial 12 h habituation period. The subjects were continuously video-recorded using a webcam (Xiaoyi Smart Web Cam; Shanghai Xiaoyi Technology) and a micro SD card (Micro SDHC EVO 32GB; Samsung) for 36 h. The recordings of behaviour were viewed at 1.5 times the actual speed by two observers.

Analysis of cats’ behaviour

Scoring of behaviour was based on an ethogram of mutually exclusive behavioural categories appropriate to a solitary caged cat. ¹ The duration of time spent in each behavioural category was recorded in sequence. The category of ‘sleep/rest’ included what appeared to be unconscious sleep, as well as conscious, quiet rest; because it was not always possible to distinguish between sleep and rest, these two behavioural states were treated as one category. In either case, the animal was in a posture in which very limited grooming, if any, was possible. The category of ‘general activity’ included moving about the cage and sitting where grooming could easily occur.

Grooming was noted as either oral or scratch grooming, and the anatomical area(s) groomed were recorded. A grooming bout was considered terminated when a non-grooming activity occurred (eg, eating, eliminating, rest), or if more than 60 s elapsed without a licking episode. Cats were sometimes seen to deliver several licks, pause for a few seconds without engaging in any other identifiable behaviour, and then continue licking; this was not considered a new grooming bout. However, to improve the accuracy of recording cumulative grooming time within prolonged grooming bouts, separate start and stop times were entered if more than 5 s of non-grooming followed a grooming episode within a grooming bout. These separate entries were then summated to determine the bout’s duration. For oral grooming, no distinction was made between incisor nibbling or tongue-stroking when grooming was directed to a single region. The anatomical regions for oral grooming were head (face washing), neck and chest, sides and back, abdomen, hindlimbs, anogenital area and tail. ¹ For scratch grooming, the anatomical regions were chin (including head rostral to the ears), ear and neck. In preliminary trials, >90% inter-observer reliability was established for the two individuals scoring the videotapes.

Data analysis

The time budget analysis was derived from data pooled from all cats, and tabulated as a percentage of total observation time. Because each subject was observed for the same amount of time, data from each individual animal contributed equally to the data set.

Sample collection and analysis

Cats were adapted to the stainless steel cage and diet for 16 days before a 10 day collection period. The cats were individually offered calculated amounts of dry extruded diet (chicken-based grain-free commercial feed, provided by Daehan Feed; Table 1). The amount was defined according to the energy requirements for adult cat maintenance, estimated as ME = 100 × BW^0.67, where ME is metabolisable energy and BW is body weight. ⁸ Food was provided twice daily (at 09:00 h and 16:00 h). Water was provided ad libitum. Litter boxes were cleaned between 08:00 h and 09:00 h, and between 15:00 h and 16:00 h.

During the collection period, food offered, food refused and faecal output were measured daily and used for analysis of digestibility. On the first day of faecal collection, all faeces were removed from the cages and discarded before 09:00 h. Faecal output was collected from this time on for the next 10 days (5 days for hair-removed faecal samples and 5 days for hair-included faecal samples). During the collection phase, total faecal outputs were collected. To ensure complete collection, cats were acclimated to a multi-tier litter box with no litter, which allowed urine to flow to the bottom and faeces to remain on the top. Fresh faecal samples (within 15 mins of defecation) were obtained during the collection phase. Fresh faecal samples were weighed and stored at −20°C until further analysis. All faeces were collected, composited, dried at 55°C in a drying oven (AMP Daw Model 18; Daihan Scientific), and ground through a 1 mm screen (Wiley Mill Intermediate; Thomas Scientific) for hair-included faecal samples.

We were unable to find published studies that conducted the removal of hair in cat faeces to compare the apparent digestibility for domestic cats using hair-included faeces and hair-removed faeces. Thus, we developed the following protocol based on our observations of cat faecal traits to obtain hair-removed faecal samples. As we collected the hair-included faecal samples, we collected fresh total faecal output and dried it at 55°C in a drying oven (AMP Daw Model 18; Daihan Scientific). We removed all the hair using pincettes and then ground the faeces through a 1 mm screen (Wiley Mill Intermediate; Thomas Scientific) for analysis (Table 2).

Table 2.

Analysed values of chemical composition of hairballs isolated from faeces

Criteria	Hairball isolated from faeces (%)
Moisture	5.67
Crude protein*	58.93
Crude ash	4.66
Crude fat	4.77
Calcium	1.20
Total phosphorus	0.69

^*To calculate the protein content from the total nitrogen content of cat hair, a conversion factor of 5.78 should be used instead of the commonly used factor of 6.25 for protein or the factor of 6.37 for milk ⁹

Experimental diet, hairball samples and excreta samples (hair-included faeces and hair-removed faeces) were analysed for contents of dry matter (procedure 930.15), ¹⁰ ash (procedure 942.05), ¹⁰ ether extract (procedure 920.39) ¹⁰ and N by using the Kjeldahl procedure with Kjeltec (KjeltecTM 2200; Foss Tecator). The experimental diet and excreta samples were analysed for crude protein (CP) content (nitrogen × 6.25; procedure 988.05) ¹⁰ and hairball samples also were analysed for CP content (nitrogen × 5.78). ⁹ The experimental diet and faeces samples were analysed for amino acid composition by using a 2-Ninhydrin procedure with a Hitach L-8900 (Beckman Instruments). Calcium and total phosphorus of samples were analysed by ICP-OES (iCAP-7400 Duo; Thermo Scientific). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) of samples were analysed by a Fiber Analyzer A2000 (ANKOM A2000; ANKOM Technology).

Statistical analysis

The experimental data were analysed using the Student’s t-test procedure of SAS, ¹¹ and a main effect in the statistical model was the length of cat hair. Individual cats were used as units for analysing behavioural observations. Differences were determined using a Fisher’s protected least significant difference. A probability of P <0.05 was accepted as statistically significant and P <0.01 was accepted as highly significant. Reported pooled SEMs were determined according to the Student’s t-test procedure of SAS.

Results and discussion

Behavioural observation

The time budget for an ethogram of mutually exclusive behavioural categories (total 24 h) is presented in Table 3. According to a previous study, ¹ domestic cats spent 50% of their time budget sleeping and resting. According to other studies,^12,13 cats can sleep for 48–55% of the time, and be drowsy for 14–28% of a 24 h day. In the present study, experimental cats spent 69–71% of a 24 h day sleeping and resting. There was no significant difference between longhair cats and shorthair cats in sleeping and resting.

Table 3.

Time budget for ethogram of mutually exclusive behavioural categories (total 24 h)

Category	Total* (%)	Longhair cats † (%)	Shorthair cats † (%)	SEM	P value
General activity	25.82	26.30	25.33	3.335	0.89
Sleep/rest	69.97	68.77	71.17	3.386	0.75
Oral groom	2.29	2.64	1.94	0.301	0.28
Scratch groom	0.18	0.24	0.12	0.047	0.26
Eat	0.89	0.99	0.79	0.076	0.21
Drink	0.48	0.59	0.36	0.127	0.42
Eliminate	0.39	0.48	0.30	0.116	0.46

^*A total of 10 domestic cats with mean ± SD age of 3.5 ± 1.38 years

^†The number of observations for each mean value was five (n = 5 for longhair cats and shorthair cats)

According to Eckstein and Hart, ¹ oral and scratch grooming accounts for 4% and 0.1%, respectively, of the overall time budget. In the present study, oral and scratch grooming accounted for 2% and 0.2%, respectively, of the overall time budget. The percentages of the time budget for oral grooming and scratch grooming in longhair cats were numerically higher than for shorthair cats, but the difference was not significant. There was no significant difference between longhair and shorthair cats in time spent on other behaviours in the time budget.

The time budget for anatomical areas of grooming is presented in Table 4. Based on a calculated overall grooming time equal to 100%, the time budget for oral grooming of all experimental cats was 92% and scratch grooming was 8%, respectively, in the present study. The region receiving the most oral grooming was the head, in the form of face washing (52%), followed by licking of the side/back (14%), hindlimb (9%), neck/chest (8%), anogenital region (3%), tail (3%) and abdomen (3%). According to Eckstein and Hart, ¹ the region that receives the most oral grooming is the face (31%), and the same ranking was recorded in this experiment. However, in the previous study hindlimb licking was in second place (21%), followed by licking of the side/back (13%), neck/chest (11%), anogenital region (10%), abdomen (9%) and tail (5%).

Table 4.

Time budget for anatomical areas of grooming^*

Zone	Total † (%)	Longhair cats ‡ (%)	Shorthair cats ‡ (%)	SEM	P value
Oral grooming	91.81	91.64	91.98	2.272	0.95
Face (wash)	52.13	50.67	53.59	3.962	0.74
Neck/chest	7.56	8.04	7.07	2.948	0.88
Sides/back	13.97	11.53	16.41	2.495	0.39
Abdomen	2.65	2.68	2.62	0.683	0.97
Hindlimb	8.66	10.32	6.99	2.505	0.55
Anogenital region	4.06	5.39	2.73	1.164	0.29
Tail	2.79	3.00	2.57	0.949	0.84
Scratch grooming	8.19	8.36	8.02	2.272	0.95
Chin	1.58	1.50	1.67	0.406	0.85
Ear	3.44	2.31	4.56	1.531	0.51
Neck	3.17	4.55	1.80	1.324	0.34

^*Calculated values based on grooming time equal to 100%

^†A total of 10 domestic cats with a mean ± SD age of 3.5 ± 1.38 years

^‡The number of observations for each mean value was five (n = 5 for longhair cats and shorthair cats)

Eckstein and Hart provided an observation cage (0.61 × 0.96 × 1.27 m) equipped with a shelf, food, water and litter to each cat for grooming behaviour analysis. ¹ It seems that the different stress intensity from the cage size and surrounding environment between the previous study and the current one caused the difference in the grooming ranking of cats. Release of corticotropin-releasing hormone due to the stress response induced a marked increase in grooming. ¹⁴ Increased grooming has been recognised to occur under certain stressful situations in the wild, ¹⁵ and has been considered to be a displacement behaviour. ¹⁶ Also, the difference of breeds and ages of the experimental animals might explain the differences in grooming rankings between the previous study and the present study. ¹ There was no significant difference between longhair cats and shorthair cats in grooming patterns in the present study.

Apparent digestibility

For measuring nutrient digestibility, an additional four cats were included so there was a total of 14 cats included in the digestibility trial. The apparent nutrient digestibility and apparent amino acid digestibility using hair-included faeces and hair-removed faeces are represented in Tables 5 and 6, respectively. There were no significant differences between the hair-included faeces or hair-removed faeces with nutrient digestibility of crude fat, calcium and total phosphorus. However, the digestibility of dry matter, CP, crude ash, ADF, and NDF of hair-removed faecal analysis was significantly higher than that of hair-included faecal analysis – about 6% (P <0.01), 7% (P <0.01), 14% (P <0.01), 12% (P = 0.01) and 10% (P <0.01), respectively. The analysed moisture value of cats’ hairballs isolated from faeces (Table 2), was 5.67%, which was higher than the moisture value of cats’ faecal samples (2.1–4.5%), and the weight ratio of the hair isolated from dried faeces was 7.4–9.8% (HS Kim and YY Kim, unpublished data).

Table 5.

Apparent nutrient digestibility using hair-included faeces and hair-removed faeces^*

Criteria	Treatment		SEM	P value
	Hair included	Hair removed
Nutrient digestibility (%)
Dry matter	74.12	80.18	0.979	<0.01
Crude protein	75.35	82.34	1.139	<0.01
Crude ash	22.51	37.33	2.547	<0.01
Crude fat	94.51	95.68	0.379	0.13
ADF	57.97	69.63	2.269	0.01
NDF	68.92	78.47	1.767	<0.01
Calcium	1.19	9.77	2.909	0.14
Total phosphorus	14.64	24.49	2.710	0.07

^*A total of 14 domestic cats with a mean ± SD age of 3.3 ± 1.38 years

^†Hair included = hair-included digestibility; hair removed = hair-removed digestibility

ADF = acid detergent fibre; NDF = neutral detergent fibre

Table 6.

Apparent amino acid digestibility using hair-included faeces and hair-removed faeces^*

Criteria	Treatment		SEM	P value
	Hair included	Hair removed
Nutrient digestibility (%)
Total amino acid	77.78	82.03	1.154	0.06
Aspartate	72.10	77.58	1.401	0.04
Threonine	73.92	79.05	1.392	0.06
Serine	74.71	80.98	1.354	0.02
Glutamic acid	78.02	81.89	1.117	0.08
Glycine	83.86	87.44	0.796	0.02
Alanine	79.54	83.42	1.018	0.06
Leucine	77.06	81.00	1.277	0.12
Arginine	85.70	88.49	0.893	0.12
Cysteine	51.14	71.13	3.372	<0.01

^*A total of 14 domestic cats with a mean ± SD age of 3.3 ± 1.38 years

^†Hair included = hair-included digestibility; hair removed = hair-removed digestibility

Hendriks announced that the amount of hair found in the faeces was 25–75 mg/kg of the body weight of the cat per day. ¹⁷ According to Lourciro et al, ⁷ hairballs isolated from the faeces of cats were 87–143 mg/cat/day. The moisture composition of hair in the faeces might influence the dry matter value of faecal samples, so the nutrient digestibility values changed. If we use the conventional method to calculate the cats’ apparent nutrient digestibility using hair-included faecal samples, the digestibility of dry matter, CP, crude ash, ADF and NDF would be underestimated by about 6%, 7%, 14%, 12% and 10%, respectively.

The apparent digestibility of amino acids such as aspartate, serine and glycine in hair-removed faeces showed higher values than those in hair-included faeces by about 6%, 6% and 3%, respectively (P = 0.04, P = 0.02 and P = 0.02, respectively). Cysteine digestibility in hair-removed faeces was significantly higher than that of hair-included faeces by about 20% (P <0.01). According to Hendriks et al, ⁹ cats’ hair has been shown to consist mainly of amino acids, and cysteine made up the largest proportion (15.8%) of the different amino acids. As Hendriks et al found, ⁹ the digestibility of CP and amino acids was revealed to be truly underestimated in the present study using the conventional apparent digestibility method of hair-included faecal samples to calculate the cats’ nutrient digestibility.

Conclusions

There was no significant difference between longhair cats and shorthair cats in the time budget of behavioural categories and grooming patterns. The digestibility of dry matter, CP, crude ash, ADF, NDF, aspartate, serine, glycine and cysteine was underestimated by about 6%, 7%, 14%, 12%, 10%, 6%, 6%, 3% and 20%, respectively, when calculated using the conventional digestibility method. Because of the chemical composition of hair included in faeces, the nutrient digestibility using hair-removed faeces was higher than that of hair-included faeces.