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Research Article

Proportion of milk samples with a specific protein and urea content depending on selected factors when evaluating dietary protein and energy balance for dairy cows

Małgorzata Jankowska, Anna Sawa, Marta Banasiak

Department of Animal Science, Unit of Cattle Breeding, UTP University of Science and Technology, 28 Mazowiecka, 85-084 Bydgoszcz, Poland

1. Acta Sci. Pol. Zootechnica, 16(4), 2017, 39‒44
2. DOI: 10.21005/asp.2017.16.4.06

Abstract. Analysis was made of the effect of herd, lactation number, day of lactation, season of testing, daily milk yield, and milk somatic cell count on the proportion of cow milk samples with a specific protein and urea content. There were not enough samples of milk containing 151–300 mg · l^–1 urea and 3.21–3.6% protein which are indicative that the dietary protein and energy are balanced. The highest percentage of milk samples with the optimum protein and urea content was observed in multiparous cows during 101–200 and 201–300 days of lactation, which had a daily milk yield of 21–30 kg and 31–40 kg in the summer season. These factors should be considered when formulating cow rations as they influence milk protein and urea levels.

Keywords: cows, milk samples, proportion of urea, proportion of protein