Effect Of Feed N-15 Incorporation Into Solid-Associated Bacteria On The In Situ Nitrogen Degradability Of N-15 Labelled Italian Ryegrass

in Animal Feed Science & Technology (2007), 135(3-4), 353-361

The objective of this study was to examine the effect of microbial contamination of the incubation residue on the in situ nitrogen degradability of Italian ryegrass. Microbial nitrogen in the bag residues ... [more ▼]

The objective of this study was to examine the effect of microbial contamination of the incubation residue on the in situ nitrogen degradability of Italian ryegrass. Microbial nitrogen in the bag residues was estimated by the feed 15N dilution procedure, and the incorporation of feed 15N into the adherent bacteria was assessed after isolating a bacterial pellet and determining its 15N enrichment. Isotopically labelled Italian ryegrass (fertilized with 15NH4 15NO3) was harvested either in spring (early cut) or in summer (late cut). Forages were incubated in the rumen of two steers for 6, 24 and48 h. The proportion of microbial N per unit of total N in the bag residue increased with incubation time, ranging from 184 to 853 mg microbial N/g totalN at 6 and 48 h, respectively. 15N enrichment in the bacterial pellet was highest after 6 h of incubation (3.6 mg 15N/g N) and then declined steadily (0.8 mg 15N/gN in 48-h residues). Microbial 15N represented up to 0.422 g/g total 15N in the bag residue, but the incorporation of feed 15N into bacterial N did not account for more than 57 mg/g 15N incubated, this incorporation rate decreasing progressively with incubation time. Correction of apparent N disappearance for microbial N resulted in higher values of N degradability, especially for the late cut grass. A further correction considering the amount of microbial 15N had little effect on the estimation of corrected N degradability values. Therefore, some of the feed 15N is incorporated into bacterial N, but this fraction has a minor effect on the estimation of total microbial N in the bag residue by the feed 15N dilution approach, and hence on the estimation of corrected degradability values. [less ▲]

Prévision de la dégradabilité in situ des matières azotées des fourrages par une méthode enzymatique.

in 3èmes Rencontres autour de la Recherche sur les Ruminants, Paris, France, 4-5 décembre 1996 (1996, December)

Approach to the use of Near Infrared Spectrometry for the estimation of microbial nitrogen contamination of forages during ruminal incubation in nylon bag.

in Giesecke, D. (Ed.) Proceedings of the Society of Nutrition Physiology. (1994, September)

In situ N degradability of fresh forages corrected for the microbial contamination determined by 15N labelling of feedstuffs or of liquid and solid associated bacteria.

Conference (1994)

Etude, à l'aide d'un fourrage frais marqué a l'azote-15, de l'influence de la finesse de broyage et du poids de l'échantillon placé dans les sachets de nylon sur la contamination microbienne des résidus.

in Annales de Zootechnie (1993, March), 42(2), 124-125

Influence du mode de conditionnement d'un fourrage vert sur sa composition chimique, la digestibilite in vitro de la matiere organique et la degradabilite in sacco de l'azote dans le rumen.

in Reproduction Nutrition Development (1990), (Supplement 2), 159-160

Fiber contents of oven-dried ray-grass cut at different stages of maturity were higher than the values obtained for freeze-dried samples. The reverse was observed for in vitro organic matter digestibility ... [more ▼]

Fiber contents of oven-dried ray-grass cut at different stages of maturity were higher than the values obtained for freeze-dried samples. The reverse was observed for in vitro organic matter digestibility. Moreover, oven-drying dramatically decreased in sacco nitrogen degradability as compared to lyophilization, preservation by freezing with liquid nitrogen and use of fresh material. [less ▲]