A series of four experiments were conducted to evaluate whether a
preconditioning period, in which adult leghorn cockerels are allowed 3 weeks to adapt to
diets containing relatively high levels of guar meal (GM) resulted in changes in digestive
tract morphology and ecology. It was expected that these changes would result in
increased utilization of GM as birds became acclimated to consuming it at high levels. In
the 1st experiment, 28 birds were fed diets containing 0, 6, 12, or 24% GM. Consuming
the 24% GM diet resulted in decreased body weight, increased small intestine, liver, and
pancreas weight, increased ceca and villus length, and increased severity of injury to the
intestinal mucosa (P < 0.05). In the 2nd experiment, 28 cockerels were subjected to a
partial cross-over experiment. Preconditioning to the 24% GM diet resulted in decreased
TMEn of GM, decreased body weight, and decreased absorptive capacity of the GI tract
as evidenced by increased energy lost via the excreta (P < 0.05). The 3rd experiment
evaluated how differences in endogenous energy losses (EEL) from 30 cockerels
affected the TMEn content of GM in birds consuming 0, 6, or 12% GM. Decreased EEL was observed in birds conditioned to 6 and 12% GM relative to the control group (P <
0.05). Further, decreased TMEn of GM was observed in birds consuming 6% GM
relative to those consuming the control diet (P < 0.05). In the 4th experiment, changes in
cecal microbiota were evaluated in 24 cockerels consuming 0, 6, or 12% dietary GM
using denaturing gradient gel electrophoresis of amplified bacterial DNA sequences.
Cecal microbiota of birds consuming 12% GM was considerably different from the
control group (similarity coefficient = 84%) with an apparent decrease in the complexity
of microbial communities. Results of these studies show that consuming 12% dietary
GM results in changes in the cecal microbial community which may be responsible for
modest increases in the TMEn of GM when compared to 6% dietary GM, which
consistently resulted in decreased TMEn values of GM. Further, determining the TMEn
value of GM appears to be highly dependent upon factors such as preconditioning diet
and timeframe and innate physiological "thresholds" which seem to initiate or limit the
maximum physiological response to preconditioning that the bird is capable of.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-08-7018 |
| Date | 14 January 2010 |
| Creators | Gutierrez, Omar |
| Contributors | Bailey, Christopher A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation |
| Format | application/pdf |
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