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Histidine dose-response effects on lactational performance and plasma amino acid concentrations in lactating dairy cows fed a metabolizable protein-deficient diet.

S. E. Räisänen

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Histidine dose-response effects on lactational performance and plasma amino acid concentrations in lactating dairy cows fed a metabolizable protein-deficient diet.
S. E. Räisänen*1, C. F. A. Lage1, M. E. Fetter1, A. Melgar1, H. A. Stefenoni1, D. E. Wasson1, S. F. Welchez1, X. Zhu1, M. Miura2, A. N. Hristov1. 1The Pennsylvania State University University Park, PA, 2Ajinomoto Co., Inc Kawasaki, Japan.

The objective of this experiment was to determine the effect of increasing dietary His levels on milk production, milk composition and plasma AA concentrations in lactating dairy cows fed a metabolizable protein (MP) deficient diet, according to NRC (2001). Twenty Holstein cows, of which 8 primiparous, [64 ± 12 d in milk, 584 ± 61 kg BW, 43.5 ± 12.4 kg milk yield (MY)], were used in a replicated 4 × 4 Latin square design with 4, 28-d periods. Treatments were: a control diet supplying 1.8% digestible (d)His of MP (His1.8) and the control diet supplemented with rumen-protected (RP)His to provide 2.4, 2.8, or 3.3% dHis of MP (His2.4, His2.8, and His3.3, respectively). Dry matter intake (DMI) and MY were recorded daily, and milk and blood samples collected at 4 time points on the last wk of each experimental period. All data were analyzed using PROC MIXED of SAS with treatment and period in the model. Square and cow within square were random effects. Linear and quadratic effects of His dose were tested. Histidine did not affect DMI (P = 0.90; averaging 21.0 kg/d; SEM = 1.95) but increased (P = 0.01) MY linearly (37.1, 38.9, 39.2 and 39.1 kg/d, respectively). Histidine had a quadratic effect (P = 0.01) on milk fat concentration (3.62, 3.32, 3.37 and 3.41%, respectively) but did not affect milk fat and energy-corrected milk yields (P ≥ 0.33). Lactose concentration and yield as well as milk true protein concentration were not affected (P > 0.10) by His. Milk true protein yield was increased linearly (P < 0.01) by His (from 1.02 kg/d for dHis1.8 to 1.10 kg/d for dHis3.3; SEM = 0.062). Plasma His concentration increased linearly (P < 0.001; 21.0, 27.0, 35.1 and 40.0 µM, respectively) with increasing His dose. In this experiment, RPHis supplementation of an MP deficient diet linearly increased milk yield up to 2.8% dHis supply of MP and linearly increased milk protein yield up to 3.3% dHis supply of MP in lactating dairy cows.

Keywords: rumen-protected histidine, milk production, milk protein.