Feeding ration of yaks of the Kyrgyz population and its influence on the biochemical composition of milk

Yaks are the large herbivorous ruminants that live in high mountain pastures at altitudes from 2,000 to 4,000 m above sea level. This environment is quite harsh, and yaks calmly tolerate extreme cold — down to minus 40 ºС. The main food of yaks are herbaceous plants, the vegetation season of which in a cold mountain climate is short, about 3–4 months, and therefore they feed mostly on wilted pasture, which is, in principle, sufficient for these animals. At the end of winter, when the amount of pasture feed decreases, the animals become malnourished and lose weight. Therefore, yak farmers often face the need to feed their animals in winter. A complete ration of an animal, along with other factors, has a significant impact on the composition of milk and its productive ability. The aim of the work is to study the chemical composition, in particular the protein fraction, of the milk of yaks living in the mountainous regions of Kyrgyzstan in comparison with the milk of yaks from different regions of the world. The object of the study was milk of yaks inhabiting the highland regions of Naryn province of Kyrgyzstan. Samples were collected and tested according to standard methods. Studies have shown that the milk of yaks from the Kyrgyz population contains more protein (5.66%) than milk from yaks in the mountains of China, Russia and Mongolia (4.95, 4.55 and 5.3%, respectively). Milk we studied is high in amino acids such as methionine, lysine, proline, phenylalanine, and alanine. Seasonal (spring, summer) changes in the protein composition (whey proteins, casein proteins), amino acid profile, total nitrogen, non-protein nitrogen of yak milk were also studied. The total content of amino acids in the milk of Kyrgyz female yaks is noticeably higher in spring (6189.96 mg/100 g) than in summer (5101.47 mg/100 g). The research results presented in this article showed that the milking season and the associated feeding ration of yaks affects the composition of milk, which is associated with the nutritional value of grass feed and its nutrient content. Spring milk contains more proteins and amino acids than summer milk, which is due to the high protein content of plants in the spring period before the flowering phase. Milk of Kyrgyz yak with proven high nutritional and biological value is an alternative to cow milk.

1. Chysyma, R.B., Kuzmina, E.E. (2017). Yak breeding of the Republic Tuva: A condition and prospects of innovational development. Journal of Dairy and Beef Cattle Breeding, 6, 15–17. (In Russian)

2. Wiener, G. (2003). The yak. Bangkok, Thailand: RAP Publication, 2003.

3. Irgit, R.S., Lushchenko, А.Е. (2021). Workshop on yaks breeding. Kyzyl: Publishing house of Tuva State University, 2021. (In Russian)

4. Luming, D., Ruijun, L., Zhanhuan, S., Changting, W., Yuhai, Y., Songhe, X. (2008). Feeding behaviour of yaks on spring, transitional, summer and winter pasture in the alpine region of the Qinghai-Tibetan plateau. Applied Animal Behaviour Science, 111(3–4), 373–390. http://doi.org/10.1016/j.applanim.2007.06.008

5. Arutyunyan, A.A., Raspopina, L.G. (2019). The features of the high-mountain animal — the yak. Young Scientist, 5(25), 31–34. (In Russian)

6. Ionov, R. N., Lebedeva, L. P. (2019). Flora of Kyrgyzstan. Kyrgyzstan Live Nature Research, 1–2, 24–34. http://doi.org/10.5281/ZENODO.4286230 (In Russian)

7. Imanberdieva, N.A., Lebedeva, L.P. (2016). Medicinal plants of At-Bashy valley in the inner Tien-Shan of Kyrgyzstan. The problems of preservation of natural resources. Scientific Result. Medicine and Pharmacy Series, 2(2), 37–43. https://doi.org/10.18413/2313-8955-2016-2-2-37-43 (In Russian)

8. Kadyrkulov, M.K. (2012). Physical geography of Kyrgyzstan. Bishkek: Innat, 2012. (In Kyrgyz)

9. Zhumalieva, A.S., Kurochkin, Yu.N., Syromyatina, M.V., Chistyakov, K.V. (2017). Dynamics of land use of the high-altitude Aksai-Chatyrkul depression of the Inner Tien-Shan (1980–2010). Geography and Natural Resources, 1, 179–187. (In Russian)

10. Lin, Y.A., Yang, Ch., Chi, F., Gu, X., Zhu, Y. (2021). Survey of the vitamin and mineral content in milk from yaks raised at different altitudes. International Journal of Food Science, 2021, Article 1855149. https://doi.org/10.1155/2021/1855149

11. Li, Н., Ma, Y., Li, Q., Wang, J., Cheng, J., Xue, J. et al. (2011). The chemical composition and nitrogen distribution of Chinese yak (Maiwa) milk. International Journal of Molecular Sciences,12(8), 4885–4895. https://doi.org/10.3390/ijms12084885

12. Kan-Ool, B.K., Ludu, B.M. (2016). Biochemical composition of milk of Tuvinian grunting cows. Siberian Herald of Agricultural Science, 4, 58–63. (In Russian)

13. Bakhtushkina, A.I., Koval, A.D. (2020). Milk production and milk chemical composition of yak females of the Altai population. Bulletin of Altai State Agricultural University, 8(190), 81–86. (In Russian)

14. Tikhomirov, I.A. (2018). Modern methods of high quality milk production technological processes control and management. Machinery and Technologies in Livestock, 3(31), 163–168. (In Russian)

15. Chasovshchikova, M.A., Gubanov, M.V. (2022). The ratio between dairy fat and milk protein in cows as an indicator of herd health. Bulletin of KSAU, 9(186), 104–110. http://doi.org/10.36718/1819-4036-2022-9-104-110 (In Russian)

16. So, S., Wanapat, М., Cherdthong, А. (2021). Effect of sugarcane bagasse as industrial by-products treated with Lactobacillus casei TH14, cellulase and molasses on feed utilization, ruminal ecology and milk production of mid-lactating Holstein Friesian cows. Journal of the Science of Food and Agriculture, 101(11), 4481–4489. https://doi.org/10.1002/jsfa.11087

17. Imanberdieva, N.A., Temirbaeva, A. (2012). Forage plants pastures of Kyrgyzstan and their chemical composition. Izvestiya Vysshih Uchebnyh Zavedeniy Kyrgyzstana, 6, 121–122. (In Russian)

18. Shukurov, E.J., Ionov, R.N., Lebedeva, L.P., Shukurov, E.E., Ionova, T.R., Zhusupbaeva, A.A. (2017). Herbaceous and animals communities of Kyrgyzstan. Bishkek: EDC “Alaine”, ED “BIOM”. 2017. (In Russian)

19. Li, H., Ma, Y., Dong, А., Wang, J., Li, Q., He, S. et al. (2010). Protein composition of yak milk. Dairy Science and Technology, 90(1), 111–117. https://doi.org/10.1051/dst/2009048

20. Permyakov, E.A., Berliner, L.J. (2000). α-Lactalbumin: Structure and function. FEBS Letters, 473(3), 269–274. https://doi.org/10.1016/S0014-5793(00)01546-5

21. Croguennec, T., O’Kennedy, В.Т., Mehra, R. (2004). Heat-induced denaturation/ aggregation of β-lactoglobulin A and B: Kinetics of the first intermediates formed. International Dairy Journal, 14(5), 399–409. https://doi.org/10.1016/j.idairyj.2003.09.005

22. Meldenberg, D.N., Polyakova, O.S., Semenova, E.S, Yurova, E.A. (2020). Development of a comprehensive milk protein composition assessment from raw materials of various farm animals for the functional products production. Storage and Processing of Farm Products, 3, 118–133. https://doi.org/10.36107/spfp.2020.352 (In Russian)

23. Pesic, M.B., Barac, М.В., Stanojevic, S.P., Vrvic, М.М. (2014). Effect of pH on heat-induced casein-whey protein interactions: A comparison between caprine milk and bovine milk. International Dairy Journal, 39(1), 178–183. https://doi.org/10.1016/j.idairyj.2014.06.006

24. Surroca, Y., Haverkamp, J., Heck, A.J.R. (2002). Towards the understanding of molecular mechanisms in the early stages of heat induced aggregation of betalactoglobulin AB. Journal of Chromatography A, 970(1–2), 275–285. https://doi.org/10.1016/S0021-9673(02)00884-1

25. Ostroumov, L.A., Shakhmatov, R.A., Kurbanova, M.G. (2011). Investigation of seasonal changes in fractional composition of milk proteins. Food Processing: Techniques and Technology, 1(20), 36а-41. (In Russian)

26. Elamanovа, R. Sh. (2022). Seasonal changes in the protein composition of khainak milk. Food Processing: Techniques and Technology, 52(3), 555–569. (In Russian). https://doi.org/10.21603/2074-9414-2022-3-2381

27. Roin, N.R., Larsen, L.B., Comi, I., Devold, T.G., Eliassen, T.I., Inglingstad, R.A. et al. (2022). Identification of rare genetic variants of the αs-caseins in milk from native Norwegian dairy breeds and comparison of protein composition with milk from highyielding Norwegian Red cows. Journal of Dairy Science, 105(2), 1014–1027. https://doi.org/10.3168/jds.2021-20455

28. Bär, C., Sutter, М., Kopp, С., Neuhaus, Р., Portmann, R., Egger, L. et al. (2020). Impact of herbage proportion, animal breed, lactation stage and season on the fatty acid and protein composition of milk. International Dairy Journal, 109, Article 104785. https://doi.org/10.1016/j.idairyj.2020.104785

29. Li, S., Ye, А., Singh, Н. (2019). Seasonal variations in composition, properties, and heat-induced changes in bovine milk in a seasonal calving system. Journal of Dairy Science, 102(9), 7747–7759. https://doi.org/10.3168/jds.2019-16685

30. Chen, Y., Qu, S., Huang, Z., Ren, Y., Wang, L., Rankin, S.A. (2021). Analysis and comparison of key proteins in Maiwa yak and bovine milk using high-performance liquid chromatography mass spectrometry. Journal of Dairy Science, 104(8), 8661–8672. https://doi.org/10.3168/jds.2021-20269

31. Khromova, L.G., Baylova, N.V., Sychev, A.I. (2021). Biological value of proteins of milk of Simmental cows produced under conditions of intensive technology. Scientific Notes Kazan Bauman State Academy of Veterinary Medicine, 247(3), 288–293. http://doi.org/10.31588/2413-4201-1883-247-3-288-292 (In Russian)

32. Shimomura, Y, Kitaura, Y., Kadota, Y., Ishikawa, Т., Kondo, Y., Xu, М. et al. (2015). Novel physiological functions of branched-chain amino acids. Journal of Nutritional Science and Vitaminology, 61(Sup), S112-S114. https://doi.org/10.3177/jnsv.61.S112

33. Nie, C., He, Т., Zhang, W., Zhang, G., Ma, Х. (2018). Branched chain amino acids: Beyond nutrition metabolism. International Journal of Molecular Sciences, 19(4), Article 954. https://doi.org/10.3390/ijms19040954

34. Akram, M., Daniyal, М, Ali, А., Zainab, R., Muhammad Ali Shah, S., Munir, N. et al. (2020). Role of phenylalanine and its metabolites in health and neurological disorders. Chapter in a book: Synucleins — biochemistry and role in diseases. IntechOpen, 2020. http://doi.org/10.5772/intechopen.83648

35. McGinnity, C.J., Riaño Barros, D.A., Guedj, Е., Girard, N., Symeon, С., Walker, Н. et al. (2021). Retrospective case series analysis of the relationship between phenylalanine: Tyrosine ratio and cerebral glucose metabolism in classical phenylketonuria and hyperphenylalaninemia. Frontiers in Neuroscience, 15, Article 664525. https://doi.org/10.3389/fnins.2021.664525

36. Holeček, M. (2018). Branched-chain amino acids in health and disease: Metabolism, alterations in blood plasma, and as supplements. Nutrition and Metabolism, 15(1), Article 33. https://doi.org/10.1186/s12986-018-0271-1

37. Zhang, S., Zeng, Х., Ren, М., Mao, Х., Qiao, S. (2017). Novel metabolic and physiological functions of branched chain amino acids: A review. Journal of Animal Science and Biotechnology, 8, Article 10. http://doi.org/10.1186/s40104-016-0139-z

38. Dimou, A., Tsimihodimos, V., Bairaktari, Е. (2022). The critical role of the branched chain amino acids (BCAAs) catabolism-regulating enzymes, branchedchain aminotransferase (BCAT) and branched-chain α-keto acid dehydrogenase (BCKD), in human pathophysiology. International Journal of Molecular Sciences, 23(7), Article 4022. https://doi.org/10.3390/ijms23074022