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Methionine supplementation at low and adequate net energy supply in lactating dairy goats.

L. Bahloul



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Methionine supplementation at low and adequate net energy supply in lactating dairy goats.
S. Lemosquet1, M. Boutinaud1, A. Leduc1, S. Binggeli2, E. Chanat1, L. Bahloul*3. 1INRAE, Agrocampus Ouest, PEGASE Saint-Gilles, France, 2Universit� Laval Quebec, QC, Canada, 3Center of Expertise and Research in Nutrition, Adisseo, France S.A.S Commentry, France.

The responses in milk yield (MY) and composition to methionine (Met) supply through the isopropyl ester of 2-hydroxy-4-methlythio butanoic acid (HMBi) at low (LE) and adequate levels (AE) of NEL (E) were investigated with a 2 � 2 factorial design on 48 multiparous Alpine goats (85 � 15 DIM, 55 � 6 kg), assigned to a randomized complete block design in 4 groups during 6 weeks. All goats received fixed amounts of hay (15.5 kg of DM per group) and of concentrates distributed individually with 0.24% of DM of HMBi added in LEMet and AEMet concentrates. A covariance-variance analysis was performed using the MIXED procedure SAS with CSN1S1 genotype, E, Met and E � Met interaction as fixed effects. The mean DMI of concentrates was 1.52 � 0.12 kg/d/goat and DMI of hay were 13.4, 14.9, 14.3 and 14.2 kg/d in LE, LEMet, AE and AEMet groups, respectively. The NEL density of LE vs. AE diets were 1.47 vs. 1.54 Mcal/kg DM, respectively with a same MP content (86 g/kg of DM; INRA, 2007). Results are shown in Table 1. Increasing Met supply increased MY at AE supply (E � Met). It increased milk true protein content (MPC) and yield (MPY) and casein content at both E levels. It tended to increase milk fat content (MFC) and increased its yield (MFY). It tended to increase the plasma concentration of Met and decreased the concentrations of AA from group 2 (Lys, Ile, Leu, Val) suggesting a higher mammary utilization of these EAA. Increasing E supply tended to increase MPY, and increased the proportion of casein in MPC. It also increased MFC, MFY, lactose content and tended to increase its yield. Supplying Met in lactating dairy goats had the same effects on milk composition than in cows but the increased MY is only observed at NEL requirement (AE).Table 1.

ItemTreatmentSEMP <
MY, kg/d3.062.933.
MPC, g/kg27.729.327.828.70.40.57<0.010.29
MPY, g/kg83.485.784.492.
MFC, g/kg38.039.439.941.
MFY, g/d1151161211312.6<
Lactose, g/kg43.042.443.943.
Lactose, g/j1311261351416.00.090.940.33
Casein, g/kg23.525.
Casein, % MPC81.080.582.881.70.8<
Met, �M22.627.526.525.81.60.470.170.07
AA group 2, �M13612916912690.10<0.01<0.05

Keywords: isopropyl ester of 2-hydroxy-4-methlythio butanoic acid (HMBi), goat, energy.