meatTheory and practice of meat processingТеория и практика переработки мяса2414-438X2414-441XФГБНУ «Федеральный научный центр пищевых систем им. В.М. Горбатова» РАН10.21323/2414-438X-2025-10-2-156-163meat-462Research ArticleСтатьиExplorative study of blood urea nitrogen (BUN), serum estrogen, and conception rate (CR) in small-scale dairy farms based on quantity of feed concentrate consumed by the cattleExplorative study of blood urea nitrogen (BUN), serum estrogen, and conception rate (CR) in small-scale dairy farms based on quantity of feed concentrate consumed by the cattlehttps://orcid.org/0000-0002-0193-4898MulyatiS.MulyatiS.

Sri Mulyati, Ph.D., Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–811–3251–106

Sri Mulyati, Ph.D., Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–811–3251–106

sri-m@fkh.unair.ac.idhttps://orcid.org/0009-0000-8949-485XAzizF.AzizF.

Fachruddin Aziz, M. Sc., Student

Faculty of Veterinary Medicine; Master Program of Reproductive Biology

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–856–4003–1825

Fachruddin Aziz, M. Sc., Student

Faculty of Veterinary Medicine; Master Program of Reproductive Biology

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–856–4003–1825

azizfachruddin14@gmail.comhttps://orcid.org/0000-0001-9421-9342KhairullahA. R.KhairullahA. R.

Aswin R. Khairullah, Ph.D., Researcher

Research Center for Veterinary Science

16911;  Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–814–5510–7656

Aswin R. Khairullah, Ph.D., Researcher

Research Center for Veterinary Science

16911;  Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–814–5510–7656

aswinrafif@gmail.comhttps://orcid.org/0000-0003-4543-1659MustofaI.MustofaI.

Imam Mustofa, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–812–3561–540

Imam Mustofa, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–812–3561–540

imam.mustofa@fkh.unair.ac.idhttps://orcid.org/0000-0002-1147-3263UtomoB.UtomoB.

Budi Utomo, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–815–5316–0631

Budi Utomo, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–815–5316–0631

budi-u-2@fkh.unair.ac.idhttps://orcid.org/0000-0002-6832-9799SriantoP.SriantoP.

Pudji Srianto, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Pudji Srianto, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

pudji-s@fkh.unair.ac.idhttps://orcid.org/0000-0002-2366-5027SuprayogiT. W.SuprayogiT. W.

Tri W. Suprayogi, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115;  Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–813–3021–5592

Tri W. Suprayogi, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115;  Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–813–3021–5592

tri-w-s@fkh.unair.ac.idUtamaS.UtamaS.

Suzanita Utama, Ph.D., Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Suzanita Utama, Ph.D., Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115; Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

suzanita-u@fkh.unair.ac.idhttps://orcid.org/0000-0002-1307-3845WurlinaW.WurlinaW.

Wurlina Wurlina, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115;  Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–812–3008–090

Wurlina Wurlina, Professor, Lecturer

Faculty of Veterinary Medicine; Division of Veterinary Reproduction

60115;  Jl. Dr. Ir. H. Soekarno, Kampus C Mulyorejo; East Java; Surabaya

Tel.: +62–812–3008–090

wurlina@fkh.unair.ac.idhttps://orcid.org/0000-0002-1279-3904AnsoriA. N. M.AnsoriA. N. M.

Arif N. M. Ansori, Ph.D., Researcher

Uttaranchal University; Universitas Airlangga; Postgraduate School; Uttaranchal Institute of Pharmaceutical Sciences; Medical Biotechnology Research Group

60286; Kampus B Dharmawangsa, Jl. Airlangga 4–6; East Java; Surabaya; 248007; India; Chakrata Rd; Uttarakhand; Dehradun; 60493;  Jl. Gunung Anyar Kidul No. 33; East Java; Surabaya

Tel.: +62–821–4464–7832

Arif N. M. Ansori, Ph.D., Researcher

Uttaranchal University; Universitas Airlangga; Postgraduate School; Uttaranchal Institute of Pharmaceutical Sciences; Medical Biotechnology Research Group

60286; Kampus B Dharmawangsa, Jl. Airlangga 4–6; East Java; Surabaya; 248007; India; Chakrata Rd; Uttarakhand; Dehradun; 60493;  Jl. Gunung Anyar Kidul No. 33; East Java; Surabaya

Tel.: +62–821–4464–7832

ansori.anm@gmail.comhttps://orcid.org/0000-0002-6013-0902AkintundeA. O.AkintundeA. O.

Adeyinka O. Akintunde, Ph.D., Lecturer

Department of Agriculture and Industrial Technology

121103; Ilishan-Remo

Tel.: +234–803–478–4244

Adeyinka O. Akintunde, Ph.D., Lecturer

Department of Agriculture and Industrial Technology

121103; Ilishan-Remo

Tel.: +234–803–478–4244

adeyinka.akintunde@gmail.comhttps://orcid.org/0000-0001-8346-5468NugrahaCh. D.NugrahaCh. D.

Chairdin D. Nugraha, Ph.D., Researcher

Research Center for Animal Husbandry

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–852–0456–3939

Chairdin D. Nugraha, Ph.D., Researcher

Research Center for Animal Husbandry

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–852–0456–3939

chairdin@gmail.comhttps://orcid.org/0000-0002-2067-717XAhmadR. Z.AhmadR. Z.

Riza Z. Ahmad, Ph.D., Researcher

Research Center for Veterinary Science

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–817–4922–649

Riza Z. Ahmad, Ph.D., Researcher

Research Center for Veterinary Science

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–817–4922–649

riza011@brin.go.idhttps://orcid.org/0000-0003-3492-292XAnggrainiL.AnggrainiL.

Lili Anggraini, Ph.D., Researcher

Research Center for Veterinary Science

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–852–7465–7948

Lili Anggraini, Ph.D., Researcher

Research Center for Veterinary Science

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–852–7465–7948

lilianggraini202403@gmail.comhttps://orcid.org/0009-0007-4692-5008LatifahL.LatifahL.

Latifah Latifah, Ph.D., Researcher

Research Center for Veterinary Science

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–851–5923–6299

Latifah Latifah, Ph.D., Researcher

Research Center for Veterinary Science

16911; Jl. Raya Bogor Km. 46 Cibinong; West Java; Bogor

Tel.: +62–851–5923–6299

latifah.sahababintang@gmail.comUniversitas AirlanggaИндонезияUniversitas AirlanggaIndonesiaNational Research and Innovation Agency (BRIN)ИндонезияNational Research and Innovation Agency (BRIN)IndonesiaUniversitas Airlangga; Uttaranchal University; Virtual Research Center for Bioinformatics and BiotechnologyИндонезияVirtual Research Center for Bioinformatics and BiotechnologyIndonesiaBabcock UniversityНигерияBabcock UniversityNigeria202506072025102156163Copyright © Mulyati S., Aziz F., Khairullah A.R., Mustofa I., Utomo B., Srianto P., Suprayogi T.W., Utama S., Wurlina W., Ansori A.N., Akintunde A.O., Nugraha C.D., Ahmad R.Z., Anggraini L., Latifah L., 20252025Mulyati S., Aziz F., Khairullah A.R., Mustofa I., Utomo B., Srianto P., Suprayogi T.W., Utama S., Wurlina W., Ansori A.N., Akintunde A.O., Nugraha C.D., Ahmad R.Z., Anggraini L., Latifah L.Mulyati S., Aziz F., Khairullah A.R., Mustofa I., Utomo B., Srianto P., Suprayogi T.W., Utama S., Wurlina W., Ansori A.N., Akintunde A.O., Nugraha C.D., Ahmad R.Z., Anggraini L., Latifah L.This work is licensed under a Creative Commons Attribution 4.0 License.https://www.meatjournal.ru/jour/article/view/462

   The purpose of this study was to measure the level of BUN in dairy cows and its influence on services per conception (S/C) rate, milk output, and the forage to concentrate (F/C) ratio.

   Oestrogen concentrations were also assessed based on BUN level and pregnancy rate. Three blood samples were taken for the measurement of estrogen on the day of AI (D0), seven days later (D + 7), and twenty-two days later (D + 22). From the entire herd, a batch of eighteen dairy cows in total were chosen at random and split to the groups based on S/C, milk output, F/C ratio, BUN, and pregnancy rate. The means of BUN based on F/C ratio showed significant difference (p < 0.05) of the results. Each group’s estrogen concentration on D0 and D + 7 did not significantly differ (p>0.05) in regards to BUN and pregnancy rate, while the group of non-pregnant cows with high BUN featured lower value. However, in D + 22, the group of non-pregnant cows with high BUN showed a lower estrogen concentration than the group of pregnant cows with low BUN (p < 0.05), while the group of pregnant cows with low BUN had a higher BUN concentration than the group of non-pregnant cows with low BUN (p > 0.05). These results indicated that while feed could alter BUN concentrations, non-feeding factors should also be taken into account. S/C and milk yield were found to provide no effect on BUN concentrations. According to these findings, a higher BUN concentration decreased the CR value, and concentrations of BUN ≥ 18 mg/dL led to lower levels of estrogen.

   The purpose of this study was to measure the level of BUN in dairy cows and its influence on services per conception (S/C) rate, milk output, and the forage to concentrate (F/C) ratio.

   Oestrogen concentrations were also assessed based on BUN level and pregnancy rate. Three blood samples were taken for the measurement of estrogen on the day of AI (D0), seven days later (D + 7), and twenty-two days later (D + 22). From the entire herd, a batch of eighteen dairy cows in total were chosen at random and split to the groups based on S/C, milk output, F/C ratio, BUN, and pregnancy rate. The means of BUN based on F/C ratio showed significant difference (p < 0.05) of the results. Each group’s estrogen concentration on D0 and D + 7 did not significantly differ (p>0.05) in regards to BUN and pregnancy rate, while the group of non-pregnant cows with high BUN featured lower value. However, in D + 22, the group of non-pregnant cows with high BUN showed a lower estrogen concentration than the group of pregnant cows with low BUN (p < 0.05), while the group of pregnant cows with low BUN had a higher BUN concentration than the group of non-pregnant cows with low BUN (p > 0.05). These results indicated that while feed could alter BUN concentrations, non-feeding factors should also be taken into account. S/C and milk yield were found to provide no effect on BUN concentrations. According to these findings, a higher BUN concentration decreased the CR value, and concentrations of BUN ≥ 18 mg/dL led to lower levels of estrogen.

services per conception (S/C)milk yieldBUNestrogenconception rateservices per conception (S/C)milk yieldBUNestrogenconception rateThis study is supported by Skema Penelitian Dasar Unggulan (PDU) Universitas Airlangga Year 2023, with grant number: 1286/ UN3.1.6/PT/2023This study is supported by Skema Penelitian Dasar Unggulan (PDU) Universitas Airlangga Year 2023, with grant number: 1286/ UN3.1.6/PT/2023ReferencesErickson, P. S., Kalscheur, K. F. (2020). Nutrition and feeding of dairy cattle. Chapter in a book: Animal Agriculture. Sustainability, Challenges and Innovations. Academic Press, 2020. doi: 10.1016/B978-0-12-817052-6.00009-4Erickson, P. S., Kalscheur, K. F. (2020). Nutrition and feeding of dairy cattle. Chapter in a book: Animal Agriculture. Sustainability, Challenges and Innovations. Academic Press, 2020. doi: 10.1016/B978-0-12-817052-6.00009-4Maltz, E., Barbosa, L. F., Bueno, P., Scagion, L., Kaniyamattam, K., Greco, L.F. et al. (2013). Effect of feeding according to energy balance on performance, nutrient excretion, and feeding behavior of early lactation dairy cows. Journal of Dairy Science, 96(8), 5249–5266. doi: 10.3168/jds.2013-6549Maltz, E., Barbosa, L. F., Bueno, P., Scagion, L., Kaniyamattam, K., Greco, L.F. et al. (2013). Effect of feeding according to energy balance on performance, nutrient excretion, and feeding behavior of early lactation dairy cows. Journal of Dairy Science, 96(8), 5249–5266. doi: 10.3168/jds.2013-6549Tyasi, T. L., Gxasheka, M., Tlabela, C. P. (2015). Assessing the effect of nutrition on milk composition of dairy cows : A review. International Journal of Current Science, 5(2), 56–63.Tyasi, T. L., Gxasheka, M., Tlabela, C. P. (2015). Assessing the effect of nutrition on milk composition of dairy cows : A review. International Journal of Current Science, 5(2), 56–63.Martens, H. (2023). Invited Review: Increasing milk yield and negative energy balance: A gordian knot for dairy cows? Animals, 13(19), Article 3097. doi: 10.3390/ani13193097Martens, H. (2023). Invited Review: Increasing milk yield and negative energy balance: A gordian knot for dairy cows? Animals, 13(19), Article 3097. doi: 10.3390/ani13193097Weiner, I. D., Mitch, W. E., Sands, J. M. (2015). Urea and ammonia metabolism and the control of renal nitrogen excretion. Clinical Journal of the American Society of Nephrology, 10(8), 1444–1458. doi: 10.2215/CJN.10311013Weiner, I. D., Mitch, W. E., Sands, J. M. (2015). Urea and ammonia metabolism and the control of renal nitrogen excretion. Clinical Journal of the American Society of Nephrology, 10(8), 1444–1458. doi: 10.2215/CJN.10311013Carty, C. I., McAloon, C. G., O’Grady, L., Ryan, E. G., Mulligan, F.J. (2020). Relative effect of milk constituents on fertility performance of milk-recorded, spring-calving dairy cows in Ireland. Journal of Dairy Science, 103(1), 940–953. doi: 10.3168/jds.2018-15490Carty, C. I., McAloon, C. G., O’Grady, L., Ryan, E. G., Mulligan, F.J. (2020). Relative effect of milk constituents on fertility performance of milk-recorded, spring-calving dairy cows in Ireland. Journal of Dairy Science, 103(1), 940–953. doi: 10.3168/jds.2018-15490Cholico, G.N., Fling, R. R., Sink, W. J., Nault, R., Zacharewski, T. (2024). Inhibition of the urea cycle by the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin increases serum ammonia levels in mice. Journal of Biological Chemistry, 300(1), Article 105500. doi: 10.1016/j.jbc.2023.105500Cholico, G.N., Fling, R. R., Sink, W. J., Nault, R., Zacharewski, T. (2024). Inhibition of the urea cycle by the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin increases serum ammonia levels in mice. Journal of Biological Chemistry, 300(1), Article 105500. doi: 10.1016/j.jbc.2023.105500Arunvipas, P., VanLeeuwen, J. A., Dohoo, I. R., Keefe, G. P., Burton, S. A., Lissemore, K. D. (2008). Relationships among milk urea-nitrogen, dietary parameters, and fecal nitrogen in commercial dairy herds. Canadian Journal of Veterinary Research, 72(5), 449–453.Arunvipas, P., VanLeeuwen, J. A., Dohoo, I. R., Keefe, G. P., Burton, S. A., Lissemore, K. D. (2008). Relationships among milk urea-nitrogen, dietary parameters, and fecal nitrogen in commercial dairy herds. Canadian Journal of Veterinary Research, 72(5), 449–453.Rajala-Schultz, P. J., Saville, W. J. A., Frazer, G. S., Wittum, T. E. (2001). Association between milk urea nitrogen and fertility in Ohio dairy cows. Journal of Dairy Science, 84(2), 482–489. doi: 10.3168/jds.s0022-0302(01)74498-0Rajala-Schultz, P. J., Saville, W. J. A., Frazer, G. S., Wittum, T. E. (2001). Association between milk urea nitrogen and fertility in Ohio dairy cows. Journal of Dairy Science, 84(2), 482–489. doi: 10.3168/jds.s0022-0302(01)74498-0Roggero, P., Giannì, M. L., Morlacchi, L., Piemontese, P., Liotto, N., Taroni, F. et al. (2010). Blood urea nitrogen concentrations in low-birth-weight preterm infants during parenteral and enteral nutrition. Journal of Pediatric Gastroenterology and Nutrition, 51(2), 213–215. doi: 10.1097/mpg.0b013e3181cd270fRoggero, P., Giannì, M. L., Morlacchi, L., Piemontese, P., Liotto, N., Taroni, F. et al. (2010). Blood urea nitrogen concentrations in low-birth-weight preterm infants during parenteral and enteral nutrition. Journal of Pediatric Gastroenterology and Nutrition, 51(2), 213–215. doi: 10.1097/mpg.0b013e3181cd270fCheng, Z., Oguejiofor, C. F., Swangchan-Uthai, T., Carr, S., Wathes, D. C. (2015). Relationships between circulating urea concentrations and endometrial function in postpartum dairy cows. Animals, 5(3), 748–773. doi: 10.3390/ani5030382Cheng, Z., Oguejiofor, C. F., Swangchan-Uthai, T., Carr, S., Wathes, D. C. (2015). Relationships between circulating urea concentrations and endometrial function in postpartum dairy cows. Animals, 5(3), 748–773. doi: 10.3390/ani5030382Sheldon, I.M., Cronin, J., Goetze, L., Donofrio, G., Schuberth, H.-J. (2009). Defining postpartum uterine disease and the mechanisms of infection and immunity in the female reproductive tract in cattle. Biology of Reproduction, 81(6), 1025–1032. doi: 10.1095/biolreprod.109.077370Sheldon, I.M., Cronin, J., Goetze, L., Donofrio, G., Schuberth, H.-J. (2009). Defining postpartum uterine disease and the mechanisms of infection and immunity in the female reproductive tract in cattle. Biology of Reproduction, 81(6), 1025–1032. doi: 10.1095/biolreprod.109.077370Sammad, A., Khan, M. Z., Abbas, Z., Hu, L., Ullah, Q., Wang, Y. et al. (2022). Major nutritional metabolic alterations influencing the reproductive system of postpartum dairy cows. Metabolites, 12(1), Article 60. doi: 10.3390/metabo12010060Sammad, A., Khan, M. Z., Abbas, Z., Hu, L., Ullah, Q., Wang, Y. et al. (2022). Major nutritional metabolic alterations influencing the reproductive system of postpartum dairy cows. Metabolites, 12(1), Article 60. doi: 10.3390/metabo12010060Melendez, P., Donovan, A., Hernandez, J., Bartolome, J., Risco, C. A., Staples, C. et al. (2003). Milk, plasma, and blood urea nitrogen concentrations, dietary protein, and fertility in dairy cattle. Journal of the American Veterinary Medical Association, 223(5), 628–634. doi: 10.2460/javma.2003.223.628Melendez, P., Donovan, A., Hernandez, J., Bartolome, J., Risco, C. A., Staples, C. et al. (2003). Milk, plasma, and blood urea nitrogen concentrations, dietary protein, and fertility in dairy cattle. Journal of the American Veterinary Medical Association, 223(5), 628–634. doi: 10.2460/javma.2003.223.628Stoop, W.M., Bovenhuis, H., van Arendonk, J. A. (2007). Genetic parameters for milk urea nitrogen in relation to milk production traits. Journal of Dairy Science, 90(4), 1981–1986. doi: 10.3168/jds.2006-434Stoop, W.M., Bovenhuis, H., van Arendonk, J. A. (2007). Genetic parameters for milk urea nitrogen in relation to milk production traits. Journal of Dairy Science, 90(4), 1981–1986. doi: 10.3168/jds.2006-434Mucha, S., Strandberg, E. (2011). Genetic analysis of milk urea nitrogen and relationships with yield and fertility across lactation. Journal of Dairy Science, 94(1), 5665–5672. doi: 10.3168/jds.2010-3916Mucha, S., Strandberg, E. (2011). Genetic analysis of milk urea nitrogen and relationships with yield and fertility across lactation. Journal of Dairy Science, 94(1), 5665–5672. doi: 10.3168/jds.2010-3916Henao-Velásquez, A. F., Múnera-Bedoya, O. D., Herrera, A. C., Agudelo-Trujillo, J. H., Cerón-Muñoz, M. F. (2014). Lactose and milk urea nitrogen: Fluctuations during lactation in Holstein cows. Revista Brasileira de Zootecnia, 43(9), 479–484. doi: 10.1590/S1516–35982014000900004Henao-Velásquez, A. F., Múnera-Bedoya, O. D., Herrera, A. C., Agudelo-Trujillo, J. H., Cerón-Muñoz, M. F. (2014). Lactose and milk urea nitrogen: Fluctuations during lactation in Holstein cows. Revista Brasileira de Zootecnia, 43(9), 479–484. doi: 10.1590/S1516–35982014000900004Huhtanen, P., Cabezas-Garcia, E. H., Krizsan, S. J., Shingfield, K. J. (2015). Evaluation of between-cow variation in milk urea and rumen ammonia nitrogen concentrations and the association with nitrogen utilization and diet digestibility in lactating cows. Journal of Dairy Science, 98(5), 3182–3196. doi: 10.3168/jds.2014-8215Huhtanen, P., Cabezas-Garcia, E. H., Krizsan, S. J., Shingfield, K. J. (2015). Evaluation of between-cow variation in milk urea and rumen ammonia nitrogen concentrations and the association with nitrogen utilization and diet digestibility in lactating cows. Journal of Dairy Science, 98(5), 3182–3196. doi: 10.3168/jds.2014-8215Guo, K., Russek-Cohen, E., Varner, M. A., Kohn, R. A. (2004). Effects of milk urea nitrogen and other factors on probability of conception of dairy cows. Journal of Dairy Science, 87(6), 1878–1885. doi: 10.3168/jds.s0022-0302(04)73346-9Guo, K., Russek-Cohen, E., Varner, M. A., Kohn, R. A. (2004). Effects of milk urea nitrogen and other factors on probability of conception of dairy cows. Journal of Dairy Science, 87(6), 1878–1885. doi: 10.3168/jds.s0022-0302(04)73346-9Xia, C., Ur Rahman, M. A., Yang, H., Shao, T., Qiu, Q., Su, H. et al. (2018). Effect of increased dietary crude protein levels on production performance, nitrogen utilisation, blood metabolites and ruminal fermentation of Holstein bulls. Asian-Australasian Journal of Animal Sciences, 31(10), 1643–1653. doi: 10.5713/ajas.18.0125Xia, C., Ur Rahman, M. A., Yang, H., Shao, T., Qiu, Q., Su, H. et al. (2018). Effect of increased dietary crude protein levels on production performance, nitrogen utilisation, blood metabolites and ruminal fermentation of Holstein bulls. Asian-Australasian Journal of Animal Sciences, 31(10), 1643–1653. doi: 10.5713/ajas.18.0125Huhtanen, P., Hristov, A. N. (2009). A meta-analysis of the effects of dietary protein concentration and degradability on milk protein yield and milk N efficiency in dairy cows. Journal of Dairy Science, 92(7), 3222–3232. doi: 10.3168/jds.2008-1352Huhtanen, P., Hristov, A. N. (2009). A meta-analysis of the effects of dietary protein concentration and degradability on milk protein yield and milk N efficiency in dairy cows. Journal of Dairy Science, 92(7), 3222–3232. doi: 10.3168/jds.2008-1352Broderick, G. A., Faciola, A. P., Armentano, L. E. (2015). Replacing dietary soybean meal with canola meal improves production and efficiency of lactating dairy cows. Journal of Dairy Science, 98(8), 5672–5687. doi: 10.3168/jds.2015-9563Broderick, G. A., Faciola, A. P., Armentano, L. E. (2015). Replacing dietary soybean meal with canola meal improves production and efficiency of lactating dairy cows. Journal of Dairy Science, 98(8), 5672–5687. doi: 10.3168/jds.2015-9563Hristov, A.N., Heyler, K., Schurman, E., Griswold, K., Topper, P., Hile M. et al. (2015). Case study: Reducing dietary protein decreased the ammonia emitting potential of manure from commercial dairy farms. The Professional Animal Scientist, 31(1), 68–79. doi: 10.15232/pas.2014-01360Hristov, A.N., Heyler, K., Schurman, E., Griswold, K., Topper, P., Hile M. et al. (2015). Case study: Reducing dietary protein decreased the ammonia emitting potential of manure from commercial dairy farms. The Professional Animal Scientist, 31(1), 68–79. doi: 10.15232/pas.2014-01360Widyobroto, W. P., Rochijan, R., Ismaya, I., Adiarto, A., Suranindyah, Y. Y. (2016). The impact of balanced energy and protein supplementation to milk production and quality in early lactating dairy cows. Journal of the Indonesian Tropical Animal Agriculture, 41(2), 83–90. doi: 10.14710/jitaa.41.2.83-90Widyobroto, W. P., Rochijan, R., Ismaya, I., Adiarto, A., Suranindyah, Y. Y. (2016). The impact of balanced energy and protein supplementation to milk production and quality in early lactating dairy cows. Journal of the Indonesian Tropical Animal Agriculture, 41(2), 83–90. doi: 10.14710/jitaa.41.2.83-90Schöbitz, J., Albarrán, M. R., Balocchi, O. A., Wittwer, F., Noro, M., Pulido, R. G. (2013). Effect of increasing pasture allowance and concentrate supplementation on animal performance and microbial protein synthesis in dairy cows. Archivos de Medicina Veterinaria, 45(3), 247–258. doi: 10.4067/S0301-732X2013000300004Schöbitz, J., Albarrán, M. R., Balocchi, O. A., Wittwer, F., Noro, M., Pulido, R. G. (2013). Effect of increasing pasture allowance and concentrate supplementation on animal performance and microbial protein synthesis in dairy cows. Archivos de Medicina Veterinaria, 45(3), 247–258. doi: 10.4067/S0301-732X2013000300004Zhao, X., Zheng, N., Zhang, Y., Wang, J. (2025). The role of milk urea nitrogen in nutritional assessment and its relationship with phenotype of dairy cows : A review. Animal Nutrition, 20(1), 33–41. doi: 10.1016/j.aninu.2024.08.007Zhao, X., Zheng, N., Zhang, Y., Wang, J. (2025). The role of milk urea nitrogen in nutritional assessment and its relationship with phenotype of dairy cows : A review. Animal Nutrition, 20(1), 33–41. doi: 10.1016/j.aninu.2024.08.007Roy, B., Brahma., Ghosh, S., Pankaj, P. K., Mandal, G. (2011). Evaluation of milk urea concentration as useful indicator for dairy herd management : A review. Asian Journal of Animal and Veterinary Advances, 6(1), 1–19. doi: 10.3923/ajava.2011.1.19Roy, B., Brahma., Ghosh, S., Pankaj, P. K., Mandal, G. (2011). Evaluation of milk urea concentration as useful indicator for dairy herd management : A review. Asian Journal of Animal and Veterinary Advances, 6(1), 1–19. doi: 10.3923/ajava.2011.1.19Yoon, J. T., Lee, J. H., Kim, C. K., Chung, Y. C., Kim, C.-H. (2004). Effect of milk production, season, parity and lactation period on variations of milk urea nitrogen concentrations and milk components of Holstein dairy cows. Asian-Australasian Journal of Animal Sciences, 17(4), 479–484. doi: 10.5713/ajas.2004.479Yoon, J. T., Lee, J. H., Kim, C. K., Chung, Y. C., Kim, C.-H. (2004). Effect of milk production, season, parity and lactation period on variations of milk urea nitrogen concentrations and milk components of Holstein dairy cows. Asian-Australasian Journal of Animal Sciences, 17(4), 479–484. doi: 10.5713/ajas.2004.479Guinn, J. M., Nolan, D. T., Krawczel, P. D., Petersson-Wolfe, C. S., Pighetti, G. M., Stone, A. E. et al. (2019). Comparing dairy farm milk yield and components, somatic cell score, and reproductive performance among United States regions using summer to winter ratios. Journal of Dairy Science, 102(12), 11777–11785. doi: 10.3168/jds.2018-16170Guinn, J. M., Nolan, D. T., Krawczel, P. D., Petersson-Wolfe, C. S., Pighetti, G. M., Stone, A. E. et al. (2019). Comparing dairy farm milk yield and components, somatic cell score, and reproductive performance among United States regions using summer to winter ratios. Journal of Dairy Science, 102(12), 11777–11785. doi: 10.3168/jds.2018-16170Elseed, A. M. A. F., Nada, Mohammed, A., Elmanan, B. A. A. (2014). Milk urea nitrogen as a monitoring tool for assesing protein nutritional status of lactating dairy cows in Khartoum North Sudan. International Journal of Development and Sustainability, 3(4), 917–922.Elseed, A. M. A. F., Nada, Mohammed, A., Elmanan, B. A. A. (2014). Milk urea nitrogen as a monitoring tool for assesing protein nutritional status of lactating dairy cows in Khartoum North Sudan. International Journal of Development and Sustainability, 3(4), 917–922.Gulinski, P., Ewa, S., Krystof, M. (2016). Improving nitrogen use efficiency of dairy cows in relation to urea in milk — A review. Animal Science Paper and Reports, 34(1), 5–24.Gulinski, P., Ewa, S., Krystof, M. (2016). Improving nitrogen use efficiency of dairy cows in relation to urea in milk — A review. Animal Science Paper and Reports, 34(1), 5–24.Horký, P. (2014). Effect of protein concentrate supplement on the qualitative and quantitative parameters of milk from dairy cows in organic farming. Annals of Animal Science, 14(2), 341–352. doi: 10.2478/aoas-2014-0008Horký, P. (2014). Effect of protein concentrate supplement on the qualitative and quantitative parameters of milk from dairy cows in organic farming. Annals of Animal Science, 14(2), 341–352. doi: 10.2478/aoas-2014-0008Zhang, J., Zheng, N., Shen, W., Zhao, S., Wang, J. (2020). Synchrony degree of dietary energy and nitrogen release influences microbial community, fermentation, and protein synthesis in a rumen simulation system. Microorganisms, 8(2), Article 231. doi: 10.3390/microorganisms8020231Zhang, J., Zheng, N., Shen, W., Zhao, S., Wang, J. (2020). Synchrony degree of dietary energy and nitrogen release influences microbial community, fermentation, and protein synthesis in a rumen simulation system. Microorganisms, 8(2), Article 231. doi: 10.3390/microorganisms8020231Castillo, A.R., Kebreab, E., Beever, D.E., France, J. A. (2000). A review of efficiency of nitrogen utilisation in lactating dairy cows and its relationship with environmental pollution. Journal of Animal and Feed Sciences, 9(1), 1–32. doi: 10.22358/jafs/68025/2000Castillo, A.R., Kebreab, E., Beever, D.E., France, J. A. (2000). A review of efficiency of nitrogen utilisation in lactating dairy cows and its relationship with environmental pollution. Journal of Animal and Feed Sciences, 9(1), 1–32. doi: 10.22358/jafs/68025/2000Chaveiro, A., Andrade, M., Borba, A. E. S., da Silva, F. M. (2011). Association between plasma and milk urea on the insemination. Iranian Journal of Applied Animal Science, 1(4), 221–225.Chaveiro, A., Andrade, M., Borba, A. E. S., da Silva, F. M. (2011). Association between plasma and milk urea on the insemination. Iranian Journal of Applied Animal Science, 1(4), 221–225.Raboisson, D., Albaaj, A., Nonne, G., Foucras, G. (2017). High urea and pregnancy or conception in dairy cows: A meta-analysis to define the appropriate urea threshold. Journal of Dairy Science, 100(9), 7581–7587. doi: 10.3168/jds.2016-12009Raboisson, D., Albaaj, A., Nonne, G., Foucras, G. (2017). High urea and pregnancy or conception in dairy cows: A meta-analysis to define the appropriate urea threshold. Journal of Dairy Science, 100(9), 7581–7587. doi: 10.3168/jds.2016-12009Tshuma, T., Fosgate, G., Webb, E., Swanepoel, C., Holm, D. (2023). Effect of temperature and humidity on milk urea nitrogen concentration. Animals, 13(2), Article 295. doi: 10.3390/ani13020295Tshuma, T., Fosgate, G., Webb, E., Swanepoel, C., Holm, D. (2023). Effect of temperature and humidity on milk urea nitrogen concentration. Animals, 13(2), Article 295. doi: 10.3390/ani13020295Consentini, C. E. C., Souza, A. H., Sartori, R., Carvalho, P. D., Shaver, R., Wiltbank, M. C. (2023). Relationships among total mixed ration nutritional components and reproductive performance in high-producing dairy herds. JDS Communications, 4(2), 138–143. doi: 10.3168/jdsc.2022-0265Consentini, C. E. C., Souza, A. H., Sartori, R., Carvalho, P. D., Shaver, R., Wiltbank, M. C. (2023). Relationships among total mixed ration nutritional components and reproductive performance in high-producing dairy herds. JDS Communications, 4(2), 138–143. doi: 10.3168/jdsc.2022-0265Mesen, T. B., Young, S. L. (2015). Progesterone and the luteal phase: a requisite to reproduction. Obstetrics and Gynecology Clinics of North America, 42(1), 135–151. doi: 10.1016/j.ogc.2014.10.003Mesen, T. B., Young, S. L. (2015). Progesterone and the luteal phase: a requisite to reproduction. Obstetrics and Gynecology Clinics of North America, 42(1), 135–151. doi: 10.1016/j.ogc.2014.10.003Bindari, Y. R., Shrestha, S., Shresthal, N., Gaire, T. N. (2013). Effects of nutrition on reproduction — A review. Advances in Applied Science Research, 4(1), 421–429.Bindari, Y. R., Shrestha, S., Shresthal, N., Gaire, T. N. (2013). Effects of nutrition on reproduction — A review. Advances in Applied Science Research, 4(1), 421–429.Silva, A. L., Detmann, E., Dijkstra, J., Pedroso, A. M., Silva, L. H. P., Machado, A. F. et al. (2018). Effects of rumen-undegradable protein on intake, performance, and mammary gland development in prepubertal and pubertal dairy heifers. Journal of Dairy Science, 101(7), 5991–6001. doi: 10.3168/jds.2017-13230Silva, A. L., Detmann, E., Dijkstra, J., Pedroso, A. M., Silva, L. H. P., Machado, A. F. et al. (2018). Effects of rumen-undegradable protein on intake, performance, and mammary gland development in prepubertal and pubertal dairy heifers. Journal of Dairy Science, 101(7), 5991–6001. doi: 10.3168/jds.2017-13230Xu, L., Yuan, Y., Che, Z., Tan, X., Wu, B., Wang, C., Xu, C., Xiao, J. (2022). The hepatoprotective and hepatotoxic roles of sex and sex-related hormones. Frontiers in Immunology, 13(1), Article 939631. doi: 10.3389/fimmu.2022.939631Xu, L., Yuan, Y., Che, Z., Tan, X., Wu, B., Wang, C., Xu, C., Xiao, J. (2022). The hepatoprotective and hepatotoxic roles of sex and sex-related hormones. Frontiers in Immunology, 13(1), Article 939631. doi: 10.3389/fimmu.2022.939631Ipsa, E., Cruzat, V. F., Kagize, J. N., Yovich, J. L., Keane, K. N. (2019). Growth hormone and insulin-like growth factor action in reproductive tissues. Frontiers in Endocrinology, 10(1), Article 777. doi: 10.3389/fendo.2019.00777Ipsa, E., Cruzat, V. F., Kagize, J. N., Yovich, J. L., Keane, K. N. (2019). Growth hormone and insulin-like growth factor action in reproductive tissues. Frontiers in Endocrinology, 10(1), Article 777. doi: 10.3389/fendo.2019.00777Xu, X.-L., Huang, Z.-Y., Yu, K., Li, J., Fu, X.-W., Deng, S.-L. (2022). Estrogen biosynthesis and signal transduction in ovarian disease. Frontiers in Endocrinology, 13(1), Article 827032. doi: 10.3389/fendo.2022.827032Xu, X.-L., Huang, Z.-Y., Yu, K., Li, J., Fu, X.-W., Deng, S.-L. (2022). Estrogen biosynthesis and signal transduction in ovarian disease. Frontiers in Endocrinology, 13(1), Article 827032. doi: 10.3389/fendo.2022.827032

The authors declare that there are no conflicts of interest present.