Using the plasma amino acid dose-response method to validate the bioavailability of methionine and lysine in Smartamine ML.

Abstract:

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Using the plasma amino acid dose-response method to validate the bioavailability of methionine and lysine in Smartamine ML.
N. L. Whitehouse*¹, S. M. Hollister¹, L. H. P. Silva¹, K. A. McLain². ¹University of New Hampshire Durham, NH, ²University of Nebraska-Lincoln Lincoln, NE.

Rumen protected sources of Met and Lys need to be held to the same scrutiny as any ingredient in their capacity to provide metabolizable Lys and Met. The primary objective of this trial was to determine the Lys and Met bioavailability of Smartamine ML using the plasma AA dose-response method. Eight multiparous Holstein cows (159 � 33 DIM) fitted with ruminal cannulas were used in a replicated 4 � 4 Latin square with 7-d periods. Treatments were (g/d): 1) 0 (CON), 2) 60 Lys + 20.5 Met abomasally infused (INF), 3) 60 Lys + 20.5 Met from Smartamine ML (SML; Adisseo), and 4) 60 Lys from a rumen-protected Lys supplement + 20.5 DL-Met from Smartamine M (RPL+SMM). Intake and milk yield were measured daily. Blood was collected from tail vein 2, 4, 6 and 8 h after the 0500h feeding the last 3 d of each period. Data were analyzed using PROC MIXED and REG procedures of SAS. Significance was declared at P ≤ 0.05. Milk yield (38.5 kg/d) and DMI (26.2 kg/d) were not affected by treatment. Plasma Lys, Met and total sulfur AA (TSAA) concentrations were increased for the 3 AA treatments compared with CON. Plasma Lys was higher for INF and SML than for RPL+SMM. Based on response slope differences using plasma Lys expressed as a % of TAA-Lys, RPL+SMM and SML were 46.7% (�4.8) and 80.4% (�4.8) as effective as INF in providing metabolizable Lys. Using plasma TSAA expressed as a % of TAA-TSAA, RPL+SMM and SML were 83.5% (�5.0) and 81.3 (�3.3) as effective as INF in providing metabolizable Met.Table 1. Plasma AA concentrations (�M) for cows fed RP-AA supplements and associated statistics

Item	CON	INF	RPL+ SMM	SML	SEM	P-value
Lysine	81.0c	120.7a	103.9b	118.8a	5.18	<0.001
Methionine	27.6b	43.9a	41.2a	42.6a	2.02	<0.001
Cystine	20.8	21.2	20.9	20.9	0.70	0.38
Cystathionine/Allocystathionine	2.2b	2.8a	2.8a	2.8a	0.22	0.04
Homocystine	2.5	2.6	2.5	2.5	0.15	0.90
Taurine	51.5	56.2	57.5	57.5	4.1	0.61
TSAA	104.6b	126.7a	124.9a	126.2a	5.1	0.005
Total AA	2272	2305	2331	2365	53.3	0.17
Metabolizable Lys, g/kg of product1	—	—	184	355	—	—
Metabolizable Met, g/kg of product2	—	—	616	122	—	—

^a—cMeans within rows differ at P < 0.05.¹ Analyzed Lys content of products: RPL 39.4% and SML 44.1%.² Analyzed Met content of products: SMM 73.8% and SML 15.0%.

Keywords: lysine, methionine, plasma.