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Performance and metabolic responses to rumen-protected methionine supplementation in lactating dairy goats fed two levels of metabolizable protein diets.

L. Bahloul

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06-24-2020

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Abstract:

W116
Performance and metabolic responses to rumen-protected methionine supplementation in lactating dairy goats fed two levels of metabolizable protein diets.
L. Bahloul*1, P. Schmidely2. 1Centre of Expertise and Research in Nutrition, Adisseo France S.A.S Commentry, France, 2Universit� Paris-Saclay, INRAE, AgroParisTech, UMR Mod�lisation Syst�mique Appliqu�e aux Ruminants Paris, France.

The objective was to evaluate the performance of alpine goats to 2 dietary CP levels supplemented with rumen protected methionine (RPM). Sixteen multiparous alpine goats (88.5 � 5.5 DIM) were randomly allocated in individual pen according to their milk CN-S1 genotype (High vs Low), BW, DIM, milk yield (MY) and milk protein content (MPC), and randomly assigned to a Low CP (LP,14%CP) vs High CP level (HP,16%CP) without RPM (Smartamine M, Adisseo) or with RPM at rate of 0.12%DM (+RPM) to cover 100% of metabolizable methionine (MetDi) requirement based on cow requirement (INRA, 2007). The trial was a crossover split-plot design for 9 wk: 2 periods of 4 wk each separated by 1 washout week. Milk and blood samples were collected before the morning feeding twice and once per week, respectively. Data were analyzed with MIXED procedure of SAS. DMI did not differ between groups. Goats fed RPM had higher MY in LP diet (3.98 vs 4.08 kg/d, CP�RPM: P = 0.02). Fat content did not differ between groups. Goats fed RPM increased MPC when fed HP diet (3.11 vs 3.21, CP�RPM: P < 0.01) especially in goats having Low CN-S1 (CN-S1�RMP: P = 0.10). Milk protein yield (MPY) did not differ between groups. Casein content increased in goats with high CN-S1 (23.6 vs 26.9 g/L, P = 0.02). Milk fat yield (MFY) increased in LP+RPM diet (117 vs 124 g/d, CP�RMP: P = 0.05). Lactose content did not differ between groups. Goats fed RPM had higher plasma BHB (0.63 vs 0.59 mM, P = 0.05), tended to have higher plasma Met (33 vs 37 �M, P = 0.10) and had lower serine (129 vs 115 �M, P = 0.03) and tyrosine (75 vs 67 �M, P = 0.04). Goats fed HP diet had higher plasma urea (0.49 vs 0.63 g/L, P < 0.01). Increasing CP did not alter plasma AA except for higher arginine (180 vs 206 �M, P = 0.05). In summary, increasing CP level did not improve performances of lactating dairy goats. An excess of MP supply could explain the poor MPY responses in Met balanced diets.

Keywords: amino acid, milk composition, dairy goats.