Article (Scientific journals)
Comparison of three 15N methods to correct for microbial contamination when assessing in situ protein degradability of fresh forages
Kamoun, Mohamed; Ammar, H.; Thewis, André et al.
2014In Journal of Animal Science, 92 (11), p. 5053-5062
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Keywords :
Forage; Microbial contamination; Nylon bag; Protein degradability; Rumen
Abstract :
[en] The use of stable15N as a marker to determine microbial contamination in nylon bag incubation residues to estimate protein degradability was investigated. Three methods using15N were compared:15N-labeled forage (dilution method, LF),15N enrichment of rumen solids-associated bacteria (SAB), and 15N enrichment of rumen liquid-associated bacteria (LAB). Herbage from forages differing in protein and fiber contents (early-cut Italian ryegrass, late-cut Italian ryegrass, and red clover) were freeze-dried and ground and then incubated in situ in the rumen of 3 steers for 3, 6, 12, 24, and 48 h using the nylon bag technique. The15N-labeled forages were obtained by fertilizing the plots where herbage was grown with15NH4 15NO3. Unlabeled forages (obtained from plots fertilized with NH4NO3) were incubated at the same time that (15NH4)2SO4 was continuously infused into the rumen of the steers, and then pellets of labeled SAB and LAB were isolated by differential centrifugation of samples of ruminal contents. The proportion of bacterial N in the incubation residues increased from 0.09 and 0.45 g bacterial N/g total N at 3 h of incubation to 0.37 and 0.85 g bacterial N/g total N at 48 h of incubation for early-cut and late-cut ryegrass, respectively. There were differences (P < 0.001) between uncorrected N degradability values and those corrected for microbial contamination with all of the methods. Apparent N degradability of the low-N, high-fiber forage (latecut ryegrass) was 0.51, whereas the corrected values were 0.85, 0.84, and 0.77 for the LF, SAB, and LAB methods, respectively. With early-cut ryegrass and red clover, the differences between uncorrected and corrected values ranged between 6% and 13%, with small differences among the labeling methods. Generally, methods using labeled forage or labeled SAB and LAB provided similar corrected degradability values. The accuracy in estimating the extent of degradation of protein in the rumen from in situ disappearance curves is improved when values are corrected for microbial contamination of the bag residue.
Disciplines :
Animal production & animal husbandry
Author, co-author :
Kamoun, Mohamed;  Département Sciences Agronomiques, Animal Science Unit, Gembloux Agro Bio-Tech, Université de Liège, Passage Deportes 2Gembloux, Belgium, Ecole Nationale de Médecine Vétérinaire, Département des Productions AnimalesSidi Thabet, Tunis, Tunisia
Ammar, H.;  Ecole Supérieure d’Agriculture de MograneMograne-Zaghouan, Tunisia
Thewis, André ;  Université de Liège - ULiège > Sciences agronomiques > Zootechnie
Beckers, Yves  ;  Université de Liège - ULiège > Sciences agronomiques > Zootechnie
France, J.;  Centre for Nutrition Modelling, Department of Animal and Poultry Science, University of GuelphGuelp, ON, Canada
López, S.;  Instituto de Ganadería de Montaña (CSIC-Universidad de León), Departamento de Produccion Animal, Universidad de LeónLeón, Spain
Language :
English
Title :
Comparison of three 15N methods to correct for microbial contamination when assessing in situ protein degradability of fresh forages
Publication date :
2014
Journal title :
Journal of Animal Science
ISSN :
0021-8812
eISSN :
1525-3163
Publisher :
American Society of Animal Science
Volume :
92
Issue :
11
Pages :
5053-5062
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 20 November 2014

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