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The influence of the 5-Hydroxytryptamine Receptor 2A (HTR2A) gene polymorphism on the temperament of Polish Red cows by using Classification and Regression Trees (CART) Cover

The influence of the 5-Hydroxytryptamine Receptor 2A (HTR2A) gene polymorphism on the temperament of Polish Red cows by using Classification and Regression Trees (CART)

Open Access
|Feb 2026

Figures & Tables

Figure 1.

CART classification tree for the first level of cow temperament assessment (calm cow/excitable cow). N = number of animals; ID = number of split; % – sample population in percentage; A, G, C – nucleobases in DNA molecule (adenine, guanine, cytosine)
CART classification tree for the first level of cow temperament assessment (calm cow/excitable cow). N = number of animals; ID = number of split; % – sample population in percentage; A, G, C – nucleobases in DNA molecule (adenine, guanine, cytosine)

Figure 2.

CART classification tree for the second level of cow temperament assessment (calm cow/excitable cow/very excitable cow). N = number of animals; ID = number of split; % – sample population in percentage; A, G, C – nucleobases in DNA molecule (adenine, guanine, cytosine)
CART classification tree for the second level of cow temperament assessment (calm cow/excitable cow/very excitable cow). N = number of animals; ID = number of split; % – sample population in percentage; A, G, C – nucleobases in DNA molecule (adenine, guanine, cytosine)

Two-level assessment of cow temperament

Animal classificationAssessment criteria
First level

calm cowthe cow got used to milking during the first 1–7 days of lactation (day 7 presented no signs of anxiety during milking and/or attempts to kick/kicking and/or shifting from one foot to the other and/or aggressive behaviour towards the milker)
excitable cowthe cow did not get used to milking during the first 1–7 days of lactation (after day 7, there were still signs of anxiety during milking and/or attempts to kick/kicking and/or shifting from one foot to the other and/or aggressive behaviour towards the milker)

Second level

calm cowthe cow got used to milking during the first 1–7 days of lactation (day 7 presented no signs of anxiety during milking and/or attempts to kick/kicking and/or shifting from one foot to the other and/or aggressive behaviour towards the milker)
excitable cowthe cow got used to milking during the first 8–14 days of lactation (day 14 presented no signs of anxiety during milking and/or attempts to kick/kicking and/or shifting from one foot to the other and/or aggressive behaviour towards the milker)
very excitable cowthe cow did not get used to milking during the first14 days of lactation (after day 14, there were still signs of anxiety during milking and/or attempts to kick/kicking and/or shifting from one foot to the other and/or aggressive behaviour towards the milker)

Cow temperament (calm/excitable) and mutation 4 reduced using the CART algorithm

Mutation 4Calm cows N (%)Excitable or very excitable cows N (%)Total (%)
AA6 (30.0%)14 (70.0%)20 (100.0%)
AG lub GG57 (54.8%)47 (45.2%)104 (100.0%)

Cow temperament (calm/excitable/very excitable) and mutation 4 reduced using the CART algorithm

Mutation 4Calm cows N (%)Excitable cows N (%)Very excitable cows N (%)Total (%)
AA or AG42 (46.1%)18 (19.8%)31 (34.1%)91 (100.0%)
GG21 (63.6%)10 (30.3%)2 (6.1%)33 (100.0%)

Production traits of Polish Red cows

No. FarmNHousing systemProduction traits

Milk (kg) x̅±SDFat (%) x̅±SDProtein (%) x̅±SD
126stall barn3297.81 ± 781.544.08 ± 0.363.31 ± 0.21
228free-stall barn3379.50 ± 597.394.30 ± 0.483.32 ± 0.16
310stall barn4230.1 ± 623.064.48 ± 0.453.34 ± 0.25
410stall barn3795.60 ± 306.884.52 ± 0.383.31 ± 0.16
55stall barn2951.60 ± 324.754.13 ± 0.213.05 ± 0.17
69stall barn2673.29 ± 407.524.48 ± 0.343.31 ± 0.13
711stall barn3281.55 ± 455.544.39 ± 0.473.19 ± 0.20
87stall barn3843.57 ± 432.404.23 ± 0.253.29 ± 0.14
910stall barn3525.80 ± 742.864.45 ± 0.563.36 ± 0.19
108stall barn2512.00 ± 1092.324.43 ± 0.473.32 ± 0.17

Characterization of identified SNPs in exon 3 of the bovine HTR2A gene

MutationMutation typeType of changeLocationNo rs
M1synonymousG>C12:16836930rs110801604
M2synonymousC>T12:16836917rs43696138
M3synonymousG>A12:16836873rs43696137
M4synonymousA>G12:16836852rs43696136

The allele and genotype frequencies for identified SNPs within the bovine HTR2A gene

MutationNGenotype frequencyAllele frequency
M130GG0.242G0.500
64GC0.526C0.500
30CC0.242

M2118CC0.952C0.976
6CT0.048T0.024
0TT0.000

M3118GG0.952G0.964
3GA0.024A0.036
3AA0.024

M416AA0.129A0.399
67AG0.540G0.601
41GG0.331

Association (comparison) between cow temperament (calm/excitable) and genotype for mutation 4

Mutation 4Calm cows N (%)Excitable or very excitable cows N (%)Total (%)
AG36 (50.7%)35 (49.3%)71 (100.0%)
GG21 (63.6%)12 (36.4%)33 (100.0%)
AA6 (30.0%)14 (70.0%)20 (100.0%)

Cow temperament (calm/excitable/very excitable) and mutation 4

Mutation 4Calm cows N (%)Excitable cows N (%)Very excitable cows N (%)Total (%)
AG36 (50.7%)13 (18.3%)22 (31.0%)71 (100.0%)
GG21 (63.6%)10 (30.3%)2 (6.1%)33 (100.0%)
AA6 (30.0%)5 (25.0%)9 (45.0%)20 (100.0%)
DOI: https://doi.org/10.2478/aoas-2025-0102 | Journal eISSN: 2300-8733 | Journal ISSN: 1642-3402
Language: English
Submitted on: Apr 24, 2025
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Accepted on: Sep 2, 2025
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Published on: Feb 15, 2026
In partnership with: Paradigm Publishing Services
Publication frequency: Volume open

© 2026 Joanna Pokorska, Agata Piestrzynska-Kajtoch, Krzysztof Adamczyk, Dominika Kułaj, Mariusz Łapczyński, Piotr Żmuda, Edyta Agnieszka Bauer, published by National Research Institute of Animal Production
This work is licensed under the Creative Commons Attribution 3.0 License.

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