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Estimation d’une nouvelle méthodologie pour estimer la valeur protéique des aliments à partir de la réponse en matière protéique du lait chez la vache laitière

Abstract : The aim of this trial is to test a new methodology to estimate feeds protein value based on their milk protein yield (MPY) response to metabolisable proteins supplies in diet. Compared to classical methods, this one could be used whatever the protein protection applied to feeds (essential oils, vegetable tannins). The prediction of the protein value of a tested feed is made from its MPY response using two control treatments of known protein value. This response is not linear because the efficiency of metabolisable proteins decreases as intake increases. We assume that, in the zone of supply variation tested, this decrease in efficiency is linear. To develop the method, four isoenergetic dietary treatments, defined by their increase in protein intake, were applied in a Latin square design of four 3-weeks periods to 24 cows divided in 6 homogenous groups of 4 cows. The two extreme treatments contained either 4.4 kg DM of energy concentrate (Control Low (CL), 97 g PDIE / kg DM) or 3.6 kg DM of soybean meal (Control High (CH), 252 g PDIE / kg DM ). The two intermediate treatments, consisting of a mixture of these two feeds (Medium Low: ML and Medium High: MH), were used to estimate their metabolisable protein value from their response in MPY. The increase in protein supply increased MPY production (896 and 964 g/d for CL and CH respectively). The estimated protein value of ML and MH from their MPY response was respectively +14 and +17 g PDIE / kg DM higher than the values calculated with the feed units system INRA (2007). This bias could be explained by CH position, situated in the upper part of MPY response to protein supplies corresponding to a low marginal efficiency. A more precise targeting of the maximum MPY response zone reduced this bias to +7 g PDIE /kg DM for ML. This limitation emphasizes the importance of diets formulation to target well the range of maximal variation of the MPY response. Nevertheless, the use of the MPY response seems to be an interesting approach for estimating the protein value of feeds, regardless of the protective techniques used.
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https://hal.inrae.fr/hal-02735833
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Submitted on : Tuesday, June 2, 2020 - 4:42:18 PM
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  • HAL Id : hal-02735833, version 1
  • PRODINRA : 462789

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Florence Dufreneix, Jean-Louis Peyraud, Philippe Faverdin. Estimation d’une nouvelle méthodologie pour estimer la valeur protéique des aliments à partir de la réponse en matière protéique du lait chez la vache laitière. 24. Rencontres autour des recherches Ruminants (3R), Institut de l'Elevage (IDELE). FRA., 2018. ⟨hal-02735833⟩

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