Dietary protein reduction on microbial protein, amino acids digestibility, and body retention in beef cattle. I. Digestibility sites and ruminal synthesis estimated by purine bases and 15N as markers1
| Autor: | Stefanie Alvarenga Santos, Gustavo Chamon de Castro Menezes, Sebastião de Campos Valadares Filho, Marcos Inácio Marcondes, P. M. Amaral, L. D. S. Mariz, Antonio P Faciola, D. Zanetti, Laura Franco Prados, M. V. C. Pacheco |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Nitrogen balance Omasum Chemistry 0402 animal and dairy science 04 agricultural and veterinary sciences General Medicine Beef cattle 040201 dairy & animal science Excretion 03 medical and health sciences Rumen 030104 developmental biology Animal science Nutrient Latin square Genetics Animal Science and Zoology Digestion Food Science |
| Zdroj: | Journal of Animal Science. 96:2453-2467 |
| ISSN: | 1525-3163 0021-8812 |
| DOI: | 10.1093/jas/sky134 |
| Popis: | The objectives of this study were to evaluate the effect of reducing dietary CP contents on 1) total and partial nutrient digestion and nitrogen balance and 2) on microbial crude protein (MCP) synthesis and true MCP digestibility in the small intestine obtained with 15N and purine bases (PB) in beef cattle. Eight bulls (4 Nellore and 4 Crossbred Angus × Nellore) cannulated in the rumen and ileum were distributed in duplicated 4 × 4 Latin squares. The diets consisted of increasing CP contents: 100, 120, or 140 g CP/kg DM offered ad libitum, and restricted intake (RI) diet with 120 g CP/kg DM. The experiment lasted four 17-d periods, with 10 d for adaptation to diets and another 7 for data collection. Omasal digesta flow was obtained using Co-EDTA and indigestible NDF (iNDF) as markers, and to estimate ileal digesta flow only iNDF was used. From days 11 to 17 of each experimental period, ruminal infusions of Co-EDTA (5.0 g/d) and 15N (7.03 g of ammonium sulfate enriched with 10% of 15N atoms) were performed. There was no effect of CP contents (linear effect, P = 0.55 and quadratic effect, P = 0.11) on ruminal OM digestibility. Intake of CP linearly increased (P < 0.01) with greater dietary CP. The NH3-N (P < 0.01) and urinary N excretion (P < 0.01) increased in response to dietary CP, whereas retained N increased linearly (P = 0.03). Liquid-associated bacteria (LAB) in the omasum had greater N content (P < 0.05) in relation to the particle-associated bacteria (PAB). There was no difference between LAB and PAB (P = 0.12) for 15N:14N ratio. The 15N:14N ratio was greater (P < 0.01) in RI animals in relation to those fed at voluntary intake. Microbial CP had a quadratic tendency (P = 0.09) in response to CP increase. Microbial efficiency (expressed in relation to apparent ruminally degradable OM and true ruminally degradable OM) had a quadratic tendency (P = 0.07 and P = 0.08, respectively) to CP increasing and was numerically greatest at 120 g CP/kg DM. The adjusted equations for estimating true intestinal digestibility of MCP (Y1) and total CP (Y2) were, respectively, as follows: Y1 =--16.724(SEM = 40.06) + 0.86X(SEM = 0.05) and Y2 = -43.81(SEM = 49.19) + 0.75X(SEM = 0.05). It was concluded that diets with 120 g/kg of CP optimize the microbial synthesis and efficiency and ruminal ash and protein NDF digestibility, resulting in a better use of N compounds in the rumen. The PB technique can be used as an alternative to the 15N to estimate microbial synthesis. |
| Databáze: | OpenAIRE |
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