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Received: February 28, 2026

Revised: March 13, 2026

Published: March 30, 2026

 

The purpose of this study was to investigate the impact of the month and season of the year on the quality characteristics of cow’s milk in the forest-steppe zone of Ukraine. The study was conducted on a cattle herd consisting of 367 dairy cows. Based on the results of analyses of milk obtained from control milking’s throughout the year, a seasonal influence on milk quality parameters was identified in relation to key climatic factors (air temperature and humidity) and the temperature and humidity index (THI). During the summer months, risky THI values were observed, reaching 77.20 in July, 81.86 in August, and 83.30 in June, which could have had a negative impact on milk quality. A significant seasonal effect on the milk’s fat, protein, and somatic cell content has beenScientific supervisor – Iryna Tkachova, Doctor of Agricultural Sciences, Senior Researcher, Livestock farming institute of NAAS of Ukraine demonstrated. Specifically, the fat content in milk was highest in February (4.668±0.070%) and January (4.125±0.049%), and lowest in July (2.817±0.042%) and August (2.792±0.044%). The protein content in the milk of the study cows was highest in October (3.696±0.020%) and lowest in June (3.001±0.025%) and July (3.007±0.021%). The fat-to-protein ratio was highest in all winter months – in February (1.345±0.034), January (1.289±0.018), and December (1.269±0.010) – and lowest in October (0.887±0.012) and August (0.907±0.014). The highest somatic cell counts were observed in the winter months: January (732.1±91.8 thousand/cm³), December (539.7±68.7 thousand/cm³), and February (513.1±66.4 thousand/cm³); the lowest counts were observed in March (228.6±42.5 thousand/cm³) and July (235.6±27.1 thousand/cm³). The least influence of the month and season of the year was observed for lactose content, milk solids-not-fat, and freezing point. The obtained results enable an understanding of the consistent seasonal variations in milk quality parameters and facilitate the adoption of more informed decisions on dairy farms to mitigate the negative impact of seasonal variations on the quality of dairy products.

 

References

Becker CA, Collier RJ, Stone AE. Invited review: Physiological effects of heat stress in dairy cows. J Dairy Sci. 2020;103(8):6751-6770 https://doi.org/10.3168/jds.2019-17929

Das R, Sailo L, Verma N, et al. Impact of heat stress on dairy animals: A review. Vet World. 2016;9(3):260-268.  https://doi.org/10.14202/vetworld.2016.260-268

Guzmán-Luna, P., Mauricio-Iglesias, M., Flysjö, A., & Hospido, A. (2022). Analysing the interaction between the dairy sector and climate change from a life cycle perspective: A review. Trends in Food Science and Technology, 126, 168–179. https://doi.org/10.1016/j.tifs.2021.09.001

Hayes, E., Wallace, D., O’Donnell, C., Greene, D., Hennessy, D., O’Shea, N., Tobin, J. T., & Fenelon, M. A. (2023). Trend analysis and prediction of seasonal changes in milk composition from a pasture-based dairy research herd. Journal of Dairy Science, 106(4), 2326–2337. https://doi.org/10.3168/jds.2021-21483

Hisira, V., Zigo, F., Kadaši, M., Klein, R., Farkašová, Z., Vargová, M., & Mudroň, P. (2023). Comparative analysis of methods for somatic cell counting in cow’s milk and relationship between somatic cell count and occurrence of intramammary bacteria. Veterinary Sciences, 10(7), 468. https://doi.org/10.3390/vetsci10070468

Jahnel, R. E., Blunk, I., Wittenburg, D., & Reinsch, N. (2023). Relationship between milk urea content and important milk traits in Holstein cattle. Animal, 17(5), 100767. https://doi.org/10.1016/j.animal.2023.100767

Kazeminia, M., Mahmoudi, R., Mousavi, S., & Mehrabi, A. (2023). Raw cow milk quality: Physicochemical, microbiological, and seasonal variation. Journal of Microbiology, Biotechnology and Food Sciences, 13(3), e10078. https://doi.org/10.55251/jmbfs.10078

Kheowsri, S., Rojanasthien, S., Semmarath, W., Stott, C. J., Sungkatavat, P., Phetkarl, T., Rueangareerat, P., Suprasert, A., Atthi, R., Chaimongkol, C., Lavilla, C., Singhanetr, S., Yiengvisavakul, V., Pisetpaisan, A., Choongkittaworn, N., Sansamur, C., & Lewchalermvong, K. (2022). Factors affecting milk composition in dairy farms located in Northern Thailand. Veterinary Integrative Sciences, 21(1), 157–173. https://doi.org/10.12982/VIS.2023.013

Kovalova, O., Vasylieva, N., Haliasnyi, I., Gavrish, T., Dikhtyar, A., Andrieieva, S., Didukh, N., Balandina, I., Obolentseva, L., & Hirenko, N. (2023). Development of buckwheat groats production technology using plasma-chemically activated aqueous solutions. Eastern-European Journal of Enterprise Technologies, 126, 59–72. https://doi.org/10.15587/1729-4061.2023.290584

Liu, J., Liu, H., Cao, G., Cui, Y., Wang, H., Chen, X., Xu, F., & Li, X. (2023). Microbiota characterization of the cow mammary gland microenvironment and its association with somatic cell count. Veterinary Sciences, 10(12), 699. https://doi.org/10.3390/vetsci10120699

Mylostyvyi, R., Izhboldina, O., Midyk, S., Gutyj, B., Marenkov, O., & Kozyr, V. (2023). The relationship between warm weather and milk yield in Holstein cows. World’s Veterinary Journal, 13, 134–143. https://dx.doi.org/10.54203/scil.2023.wvj14

Nahusenay, H., Tola, A., Sisay Tessema, T., Vipham, J., & Woldegiorgis, A. Z. (2023). Seasonal comparison of microbial hygiene indicators in raw and pasteurized milk and cottage cheese collected across dairy value chain in three regions of Ethiopia. Foods, 12(24), 4377. https://doi.org/10.3390/foods12244377

Nunes, J. C., Silva, M. N. L. R. d., Perrone, D., & Torres, A. G. (2017). Seasonal Variation in Fat Quality and Conjugated Linoleic Acid Content of Dairy Products from the Tropics: Evidence of Potential Impact on Human Health. Foods, 6(8), 61. https://doi.org/10.3390/foods6080061

Ormston, S., Qin, N., Faludi, G., Pitt, J., Gordon, A. W., Theodoridou, K., Yan, T., Huws, S. A., & Stergiadis, S. (2023). Implications of organic dairy management on herd performance and milk fatty acid profiles and interactions with season. Foods, 12(8), 1589 https://doi.org/10.3390/foods12081589

Pavkovych С., Vovk С., Ohorodnyk Н., Dudar І., Tkachuk В., Kozak Р., & Ratskyi М. (2025). The influence of season on the quality indicators and fatty acid composition of cow’s milk. Bulletin of Lviv National Environmental University. Series Agronomy, (29), 197–201. https://doi.org/10.31734/agronomy2025.29.197

Regulation (EC) No. 853/2004 of the European Parliament and of the Council of 29 April 2004 laying down specific hygiene rules for food of animal origin. Official European Journal Union L139/55, 30.04.2004. http://data.europa.eu/eli/reg/2004/853/oj

Salfer I.J., Dechow C.D., Harvatine K.J. (2019). Annual rhythms of milk and milk fat and protein production in dairy cattle in the United States. J Dairy Sci. 2019 Jan;102(1):742-753. https://doi.org/10.3168/jds.2018-15040

Stojnov, M.; Penev, T.; Dimov, D.; Marinov, I. (2024), Effect of Calving Season on Productive Performance of Dairy Cows. Dairy, 5, 217–228. https://doi.org/10.3390/dairy5010018

Tadesse A., Gebremichael D., Hailay B., Hailemariam F., Hadgu H., Kalayu G. (2024). The effect of season and agro-ecology on physicochemical properties of cow’s raw milk in Central and North-Western Zone of Tigray, Ethiopia. Heliyon, Vol. 10 (20), e39050, https://doi.org/10.1016/j.heliyon.2024.e39050

Thom, E.C. (1958). Cooling degree days. Air Cond. Heat. Vent., 55, 65–69.

Timlin, M., Tobin, J. T., Brodkorb, A., Murphy, E. G., Dillon, P., Hennessy, D., O’Donovan, M., Pierce, K. M., & O’Callaghan, T. F. (2021). The impact of seasonality in pasture-based production systems on milk composition and functionality. Foods, 10(3), 607. https://doi.org/10.3390/foods10030607

Tkachova I., Prusova G., Petrash V., Tkachov A. (2025). Stressful seasonal factors of influence on milk productivity and quality of cow’s milk. Scientific and Technical Bulletin of Livestock farming institute of NAAS, 134:197-207. Doi: 10.32900/2312-8402-2025-133-197-207

Tkachova I., Prusova G., Petrash V., Tkachov A., Marchenko V. (2025). Efficacy of a low protein feedstuff in feeding dairy cattle. Scientific and Technical Bulletin of Livestock farming institute of NAAS, 135: 161-170. doi: 10.32900/2312-8402-2025-135-161-170

Zazharska, N. V., BibenІ. A., & Zazharska, N. M. (2023). Cow’s milk quality indicators. Materials of the scientific and practical online conference “Food safety and quality in the One Health concept” (Lviv, June 1–2, 2023): 18-19.

Zazharska, N. V., BibenІ. A., & Zazharska, N. M. (2024). Influence of the season on the main components of cow milk in Ukraine. Regulatory Mechanisms in Biosystems, 15(3), 423-428. https://doi.org/10.15421/022459