An investigation of carbohydrate and protein degradation ratios, nitrogen to energy synchronization and hourly effective rumen digestion of barley: effect of variety and growth year

Peiqiang Yu*, K. Hart, L. Du

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (SciVal)

Abstract

The objective of this study was to investigate rumen available soluble,
insoluble and total protein (CP), estimated structural (SC) and
non-structural carbohydrate (starch: ST), degradation characteristic
ratios and hourly effective degradation of six barley varieties during
three consecutive growth years (2003, 2004, 2005). The magnitude of the
differences was determined between the varieties and growth years.
Measured degradation kinetics included soluble fraction (S),
undegradable fraction (U), lag time (T0) and rate of degradation (Kd)
of the insoluble but degradable fraction (D). Rumen available soluble,
insoluble, and total N, SC and ST and the rumen degradation
characteristic ratios were determined using the Tamminga rumen
degradation ratio system. Characteristics of the hourly effective
degradation between N and carbohydrate (CHO) among the six barley
varieties for 3 years were also studied. The degradation ratios included
were total rumen available N and carbohydrate ratio (FN/FCHO), rumen
available soluble N and carbohydrate ratio (SN/SCHO), and rumen
available insoluble N and carbohydrate ratio (EN/ECHO). Results show
that both the barley variety and growth year had a significant effect on
degradation kinetics (S, D, U, T0 and/or Kd).
Differences in the ratio of FN/FCHO among varieties ranged from 16.6 to
19.0 g/kg (p < 0.01). There was no difference in SN/SCHO
(p > 0.05) with an average of 4.9 g/kg. The difference in the EN/ECHO
ratio tended to be significant among the varieties (p = 0.069) ranging
from 18.4 to 21.3 g/kg. Differences in the hourly effective degradation
between N and CHO were relatively small at shorter incubation times
(2–4 h) However, as the length of rumen incubation increased (12–24 h),
much larger differences in the rate of effective hourly degradation were
observed. In conclusion, both barley variety and growth year had
significant effects on rumen degradation kinetics. The mean FN/FCHO
ratio of 17.2 (16.6–19.0) was observed for the six barley varieties in
this experiment. All barley varieties exhibited a less optimal rumen
fermentation ratio (17.2 < optimum: FN/FCHO = 25 to 33 g N per kg
CHO). The large differences in the degradation kinetics, characteristics
ratios and hourly effective degradation among barley varieties and
growth years may help to explain some of the large variations that are
seen in cattle performance.

Original languageEnglish
Pages (from-to)555-567
Number of pages13
JournalJournal of Animal Physiology and Animal Nutrition
Volume93
Issue number5
DOIs
Publication statusPublished - Oct 2009

Keywords

  • STARCH
  • CULTIVARS
  • growth year
  • DVE/OEB-SYSTEM
  • GRAIN
  • degradation ratio
  • CONCENTRATE
  • EXTENT
  • MILK-PRODUCTION
  • HULL-LESS BARLEY
  • LACTATING COWS
  • hourly effective degradation
  • DAIRY-COWS
  • barley variety
  • optimum rumen fermentation

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