Effect of Varying Dietary Crude Protein Level on Feed Intake, Nutrient Digestibility, Milk Production, and Nitrogen Use Efficiency by Lactating Holstein-Friesian Cows
Date
2020-12-19
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MDPI
Abstract
The effect of dietary crude protein (CP) level on intake, digestibility, milk production,
and nitrogen (N) use efficiency was studied. Twenty-four Holstein-Friesian cows (17 multiparous
and seven primiparous) were grouped by parity, days in milk, milk yield, and live weight into six
blocks of four, and randomly assigned to four total mixed ration (TMR) treatments, containing 141,
151, 177, or 210 g CP/kg dry matter (DM), over 28 day experimental periods. Apparent total-tract DM
and fiber digestibilities and milk fat composition were similar across treatments. Milk protein and
urea-N compositions, and urinary and manure N excretion increased linearly, while milk N efficiency
(MNE) decreased linearly with increasing CP. DM intake was highest with the 177 diet, while CP
intake increased linearly with increasing CP, peaking at 200 g/kg DM. Milk yield increased with CP
intake for the three lower CP levels, peaking at 176 g CP/kg DM. The further increase in CP level
from 177 to 210 g/kg DM did not result in improved milk yield, but resulted in decreased milk N
secretion and increased urinary N excretion. In summary, milk protein composition increased linearly
with increasing CP, accompanied by a linear decrease in MNE, resulting in a bell-shaped relationship
between milk yield and dietary CP level.
Description
Publication history: Accepted - 17 December 2020; Published online - 19 December 2020
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Article
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Keywords
dietary crude protein, milk yield, milk N efficiency, total mixed ration
Citation
Katongole, C.B. and Yan, T. (2020) ‘Effect of Varying Dietary Crude Protein Level on Feed Intake, Nutrient Digestibility, Milk Production, and Nitrogen Use Efficiency by Lactating Holstein-Friesian Cows’, Animals. MDPI AG. doi:10.3390/ani10122439