Quantitative meta-analysis on the effects of defaunation of the rumen on growth,intake and digestion in ruminants |
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| Institution: | 1. INRA, Unité de Recherches Zootechniques Prise d’eau, Petit-Bourg, 97170 Guadeloupe, French West Indies;2. INRA-INA PG, Unité de Physiologie de la Nutrition et Alimentation 16 rue Claude Bernard, 75005 Paris, France;1. College of Animal Science and Technology and State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China;2. Department of Animal Sciences, The Ohio State University, Columbus, OH 43210-1094, USA;1. Dipartimento di Medicina Veterinaria, Università degli Studi di Perugia, 06126 Perugia, Italy;2. Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA;3. Dipartimento di Scienze Farmaceutiche, Università degli Studi di Perugia, 06123 Perugia, Italy;1. Innovation Center for US Dairy, Rosemont, IL 60018;2. Animal Breeding and Genomics, Wageningen University & Research, 6700 AH Wageningen, the Netherlands;3. Department of Animal Science, The Pennsylvania State University, University Park 16802;4. Department of Animal Science, University of California, Davis 95616;5. Foundation for Food and Agriculture Research, Washington, DC 20004;6. Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348 |
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| Abstract: | A quantitative meta-analysis was applied on 90 publications and 169 comparisons dealing with defaunation of the rumen (removal of protozoa from the rumen) in order to point out the major quantitative effects of defaunation and identify interfering factors. Generally speaking defaunation significantly (P<0.01) increased average daily gain (11% on average, 64 trials) but did not affect dry matter intake. As a consequence, defaunation improved feed conversion efficiency (P<0.05). These different effects were especially obvious as diets were both high in forage and low in nitrogen and as animals had a low growth potential. Defaunation significantly (P<0.001) decreased organic matter digestibility (−1.7 units, 52 trials) and cell wall carbohydrate digestibility (−5.7 units, 15 trials). The same trend was observed for rumen digestibility. On the other hand, duodenal nitrogen flow, expressed as a ratio of nitrogen intake, was enhanced by defaunation (P<0.001). Duodenal microbial nitrogen flow, expressed as the percentage of live-weight, increased by 21% after defaunation (P<0.05). The latter two results may account for the lower ammonia concentration in the rumen (−50.3 mgNNH3/l, 75 trials) and the higher microbial synthesis efficiency (11.8 g microbial N/kg OMDr 19 trials) observed for the ciliate-free animals (P<0.001). The level of concentrate in the diet strongly interfered with the effect of defaunation on the pH in the rumen. pH in the rumen was increased by defaunation with diets containing a high level of concentrate (PCO≥50%), whereas it decreased with diets containing a low level of concentrate. The molar proportion of propionic acid was enhanced by defaunation, whereas the molar proportion of butyric acid was lowered (P<0.01) by defaunation, in the ruminal pool of volatile fatty acids (VFA). Finally, defaunation increased the ruminal volume and the liquid phase outflow rate (P<0.05), but to a lesser extent. We consider that these results strongly suggest a more efficient use of nutrients in ciliate-free animals, especially when they are given poor diets limiting animal production. |
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