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Effets de la défaunation de ruminants sur les performances de production, en fonction de la ration ingérée. Etude des variations de la protéosynthèse et de la cellulolyse microbienne ruminale

Abstract : The aim of this thesis was to evaluate defaunation as a technique, that allows a better nutrition of ruminants. Defaunation lead to an increase of non ammonia-nitrogen flow at the duodenum (NAN duo.). However, literature studies indicate that defaunation effect on animal production (meat, milk and wool) is varying. Our hypothesis is that the nitrogen / energy ratio (PDIN / UF) of the diet is the main factor responsible for the observed variyng effects of defaunation. The objectives were : 1) To determine the law of animal response to defaunation, generally speaking and in the specific context of the humid tropical area. 2) To determine the impact of defaunation on the parameters of digestion that may explain animal response to defaunation, especially microbial proteosynthesis and cellulolysis. First of all, the statistical analysis (meta-analysis) of the literature data allowed us to establish the global laws of animal response to defaunation. Secondary, the study of four experimental diets composed of fresh forage (Digitaria decumbens) containing 50, 60, 70 and 90 g (PDIN / UF) was elaborated. In a second study, four other diets, composed of fresh forage (Digitaria decumbens ) and concentrate (maize and soya meal) , and containing 80, 100, 120 and 140 g (PDIN / UF) were also tested. Meat production was determined by the measurements of average daily growth (ADG) on faunated and defaunated lambs , with the 8 dietary profiles (8 PDIN / UF ratios). Measurements of intestinal nitrogen flows were made on fistulated adult rams, faunated and defaunated, allowed us to estimate proteosynthesis. Microbial cellulolysis was estimated by both in sacco dry matter degradability technique, ruminal fiber (NDF) digestibility and ruminal glycolytic activity, on the same preceding rams. The results of the bibliographic synthesis indicate that defaunation led to the increase of animal growth, on average by 10 % (P < 0.01, 132.6 vs 118.7 ± 5.2 g/d). In experimental studies defaunation led to an increase of ADG for mixed diets ( PDIN / UF > 80) (P < 0.03, 184.1 vs 165.9 ± 9.3 g/d).No effect was observed on forage diets (ADG = 76 ± 3 g/j), except for diet contaning 50 PDIN/UF (25 vs 49 ± 11 g/d). The 20 % increase of intestinal nitrogen flow (microbial and dietary) after defaunation, contributes to the increased amounts of absorbed nitrogen nutrients. In experimental studies, defaunation led to a significant increase of this flow by 20% for mixed diets, and by 11% for forage diets. The bilbliographic synthesis indicated an enhancement of the shape of volatil fatty acids (VFAs) in the rumen (increase of propionate) after defaunation, whereas microbial cellulolysis decreased ( - 4.7% DrNDF). The increased intestinal nitrogen flow and the enhanced shape of VFAs contribute to the enhanced metabolic use of energetic nutrients. Thus, defaunation led to an increase of food conversion efficiency (- 1.4 g DM / g growth). These results are confirmed by our experimental diets studies. As a conclusion, the nitrogen /energy ratio of the diet modulate defaunation effect, while energy is not the growth limiting factor. The interest of defaunation in humid tropical area need to be confirmed, especially for young forage and sugar cane (low on nitrogen, high on glycoside).
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Submitted on : Tuesday, May 6, 2003 - 8:00:00 AM
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  • HAL Id : pastel-00000348, version 1
  • PRODINRA : 245327

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Maguy Eugène. Effets de la défaunation de ruminants sur les performances de production, en fonction de la ration ingérée. Etude des variations de la protéosynthèse et de la cellulolyse microbienne ruminale. Sciences du Vivant [q-bio]. INAPG (AgroParisTech), 2002. Français. ⟨NNT : 2002INAP0015⟩. ⟨pastel-00000348⟩

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