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Identification of dietary and physiological factors potentially impeding responses of lactating dairy cows to dietary fortification in metabolizable methionine: A meta-analysis.

L. Bahloul

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06-24-2020

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Abstract:

W118
Identification of dietary and physiological factors potentially impeding responses of lactating dairy cows to dietary fortification in metabolizable methionine: A meta-analysis.
L. Bahloul*1, C. Loncke2. 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.

This study aimed to establish response equations on milk protein content (MPC) and milk protein yield (MPY) to rumen protected methionine (RPM) supplementation and to determine response variation variables (interfering factors). Meta-analyses were applied using Minitab (v.17) software on published data (25 experimental groups and 36 treatments) using RPM as Smartamine M or Metasmart (Adisseo), selected from RPM database of peer reviewed publications. Diets were characterized according to INRA 2007 feeding system for dairy. Lactating dairy cows consumed on average 20.3 � 4.1kg DM, 172 � 18.2g CP/kg DM and 1643 � 70MJ NEl/kg DM. Robust within-study models were obtained to predict MPC (R2adj = 0.94, RMSE = 0.04), and MPY (R2adj = 0.98, RMSE = 32.4g/d) to RPM based on the metabolizable methionine expressed as % metabolizable protein (MetDi %PDI). The MPC model suggested that an increase of 0.7%MetDi induced an increase of 0.13%MPC. The within-study slopes were positively affected by % concentrate, HisDi, digestible OM and NEL (P < 0.1). For a same %MetDi, the MPC increased with GluDi content (P < 0.05) and decreased with fat content (P < 0.1). The MPY model indicated an average increase of 72g and an increase of 104 and 40g MPY/d for an increase of 1%MetDi in early and middle lactation. The within-study slopes were positively affected by DMI, and starch content (P < 0.05) and negatively by fermentable OM and IleDi content (P < 0.05). For a same %MetDi, the MPY increased with DMI, starch, ME, NE, and RUP content (P < 0.01) and decreased with fat content, fermentable OM, LysDi, ThrDi, ValDi, IleDi, PheDi, AspDi, SerDi, GlyDi and AlaDi content (P < 0.01). In summary, this work showed that is possible to predict the responses of lactating dairy cows as function of RPM and figure out interfering factors from diets that could affect these responses. These results provide deeper insight to biology processes and may help improving dietary formulation.

Keywords: meta-analysis, amino acids, ruminant.