Responses in Urea and True Protein of Milk to Different Protein Feeding Schemes for Dairy Cows

Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348, USA.
Journal of Dairy Science (Impact Factor: 2.57). 12/1995; 78(11):2424-34. DOI: 10.3168/jds.S0022-0302(95)76871-0
Source: PubMed


Four multiparous Holstein cows were used in a 4 x 4 Latin square to investigate the effects of protein concentration, degradability, and quality on plasma urea concentration and milk N constituents. Diets varied in the amount and proportion of RDP and RUP relative to NRC requirements: diet 1, excessive RDP, deficient RUP; diets 2 and 3, balanced for RDP and RUP; and diet 4, excessive RDP, balanced for RUP. Diet 3 was formulated for optimal AA balance as predicted by the Cornell Net Carbohydrate and Protein System. Diets contained 34% corn silage, 19% alfalfa haylage, and 49% concentrate (DM basis). Concentrates varied in amounts of urea and soybean, corn gluten, and fish and blood meals. Concentrations of urea N and NPN in milk varied among diets: diet 1, 19 and 34 mg/dl; diet 2, 16 and 31 mg/dl; diet 3, 15 and 30 mg/dl; and diet 4, 23 and 39 mg/dl, respectively. Increases in NPN concentration were attributed to increases in the urea fraction of NPN. Intake of RUP and AA balance influenced milk true protein content; diet 1, 2.89%; diet 2, 2.90%; diet 3, 3.01%; and diet 4, 2.95%. the proportions of true protein and urea in milk are influenced by CP concentration, protein type, and protein quality.

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    • "of the milk non-protein nitrogen. Milk urea nitrogen (MUN) concentration for individual cow ranges from 8 to 25 mg/dL while optimum concentration for a herd ranges from 12 to 17 mg/dL (Hwang et al. 2000; Baker et al. 1995; Roseler et al. 1993). Average MUN values may range from 10 to 14 mg/dL (Moore and Verga, 1986; Carlsson and Pehrson, 1994). "

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    • "iktorsson , 1983 ; Oltner et al . , 1985 ) . If the amount of energy supplied in the feed is adequate , milk urea nitrogen is indicative for protein status , i . e . , higher levels with excess protein provided and lower levels with deficit levels of protein ( Roseler et al . , 1993 ) , but also type of protein fed will affect the protein status ( Baker et al . , 1995 ) . The associations found in the present study between DIM , and LDH or NAGase were similar to the findings of Chagunda et al . ( 2006 ) . Unlike in our study , they also found a significant association between SCC and DIM , which others also have shown ( Brolund , 1985 ; Laevens et al . , 1997 ; Schepers et al . , 1997 ) . However , i"
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    • "Urea excreted in the urine is directly proportional to both the amount of BUN and that of MUN. Therefore, urinary ammonia can be predicted either from MUN or BUN (Baker et al., 1995; Jonker et al., 1998; Kohn et al., 2002). The MUN and BUN levels in the present study indicated that dietary protein was not fed in excess and adding dietary PE likely decreased environmental nitrogen excretion. "
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