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Title: The use of blood metabolites as indices in the assessment of protein status in ruminants
Author: Liu, Shimin
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1995
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Blood metabolites in sheep and cattle were assessed as indicators of protein status. Four experiments (Expt) were conducted with steers and sheep nourished wholly by intragastric infusions. In Expt 1, three steers (340 kg) were infused with 3 levels of volatile fatty acids (VFA) at 0, 300 and 600 KJ/kgW0.75.d and 6 levels of casein (0, 200, 400, 650, 1500 and 2500 mg N/kgW0.75.d). Each treatment was imposed for 5 or 6 days. In Expt 2, two steers were infused with 10 mg N/kgW0.75 .d and 450 KJ/kgW0.75.d VFA for 4 weeks. In two sheep experiments, five groups of lambs (35 kg) were infused with 500 mg N/kgW 0.75.d for 2 weeks and N input was then altered to 1500, 500, 100, 50 mg/kgW0.75.d for 6 weeks or 10 mg/kgW0.75.d for 4 weeks. Non-protein energy was constant at 500 KJ/kgW0.75.d. Protein status, defined as cumulative N balance (CNB) over the 6 week period relevant to the initial total body N (CNB/TN, %) in sheep were +33, +4, -23 and -15% respectively. The concentrations of serum insulin-like growth factor-1 (IGF-1), plasma fibronectin (FN) and urea responded rapidly to alterations in N input, but less to changes in protein status. They were all correlated with daily nitrogen balance. Plasma concentrations of total protein (TP) were insensitive to alterations in N input but reflected changes in protein status. Protein status can therefore be estimated from TP (g/l) as: CNB/TN, % = 41.65 A˙ (3.35 - 0.034 x TP, g/l) - 39, or from plasma total protein-N content (PTPN, g): CNB/Tn (%) = 21.1 - 170 A˙ (1 + 0.31 x PTPN, g). The concentrations of IGF-1, FN and urea at N equilibrium were 25 pmol/ml, 228 mug/ml and 2.2 mmol/l for steers, and 14 pmol/ml, 196 mug/ml and 2.3 mmol/l for sheep. If concentrations are above these values, daily NB will be positive, and vice versa.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available