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Performances and plasma energetic parameters in lactating dairy goats fed 3 levels of metabolizable methionine.

L. Bahloul

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06-24-2020

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Abstract:

W120
Performances and plasma energetic parameters in lactating dairy goats fed 3 levels of metabolizable methionine.
P. Schmidely1, L. Bahloul*2. 1Universit� Paris-Saclay, INRAE, AgroParisTech, UMR Mod�lisation Syst�mique Appliqu�e aux Ruminants Paris, France, 2Centre of Expertise and Research in Nutrition, Adisseo France S.A.S Commentry, France.

We characterized milk production and composition, and plasma parameters response to 3 levels of metabolizable methionine (MetDi) in 24 early-lactation Alpine goats (31 � 3 DIM) genotyped for milk casein aS1. The 3 diets (14% CP, NEL = 1580 kcal/kg DM) supplemented with rumen-protected MetDi (RPM; isopropyl ester of 2-hydroxy-4-methylthio butanoic acid (HMBi, Metasmart, Adisseo) provided 90 (CTL), 100 (RPM100), and 110% (RPM110) of MetDi requirement based on cow requirement (INRA, 2007). The trial was conducted as a 3-groups randomized block design for 12 wk, with 2-wk covariate period. Goats were randomly allocated to their experimental TMR at the end of wk 2 according to their aS1 genotype (High vs Low), BW, DIM, milk yield (MY) and milk protein content (MPC). Milk and blood samples (before morning feeding and milking) were collected twice per wk and weekly, respectively. Data were analyzed using the MIXED procedure of SAS for repeated data with aS1 genotype and MetDi level as fixed factors. DMI did not differ between groups. Compared with Low aS1 goats, those with High genotype had higher MPC (+1.0 g/kg), higher milk fat content (+2 g/kg), with no difference in MY. Compared with CTL goats, RPM100 or RPM110 goats had similar MY (3.7, 3.7, 3.9 kg/d, respectively), similar fat, lactose and urea concentrations in milk. The RPM100 goats had significantly (P < 0.07) higher MPC (34.9 g/kg) than CTL (33.5 g/kg) goats. Compared with CTL goats, RPM100 or RPM110 goats had numerically higher protein yield: 123, 128 and 131 g/d (P < 0.25). MetDi supplementation � aS1 genotype interaction was not significant on MPC or protein yield. Compared with CTL goats, RPM100 or RPM110 goats had similar glucose, urea, BHB and insulin plasma concentration, but lower NEFA (0.19, 0.13, 0.16 �M, P < 0.05). In conclusion, dietary MetDi recommendation in cows (2.5% metabolizable protein) can be used in goats whatever their aS1 genotype.

Keywords: metabolizable methionine, milk composition, dairy goats.