Bioavailability of Amino Acids of Soybean Meal in Broilers Subjected to Heat Stress
The effect of high ambient temperature (35 vs 21°C) and acclimation during 5 and 6 week of age on the bioavailability of protein and amino acids was investigated in broilers. Two experiments were conducted to achieve the above objectives. In both experiments, equal numbers of chickens (90 birds:...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/10685/1/FP_2006_28.pdf |
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| Summary: | The effect of high ambient temperature (35 vs 21°C) and acclimation during 5 and 6
week of age on the bioavailability of protein and amino acids was investigated in
broilers. Two experiments were conducted to achieve the above objectives. In both
experiments, equal numbers of chickens (90 birds: 45 Male, 45 Female) were
assigned to three groups namely 2 weeks heat stress (heat acclimated), I week heat
stress (non-heat acclimated) and no-heat stress. During the 28-35 days, the 2 weeks
heat stress group was challenged to heat stress for 180-min every day. During the
35-43 days, the 1 week heat stress group was challenged to heat stress as well. The
no-heat stress group was kept in standard temperature (21 °C) as control. Basal diet
which contained soybean meal as a sole source of protein was fed to all birds during
day 39-41 as adaptation period. Following this, the birds undergone 24 h fasting.
Assay diet was then fed to all birds for one hour before starting the heat challenge.
For Experiment I, Assay diet was the same with basal diet without methionine
suplimentation and for Experiment 2, it was a nitrogen free diet. Feed conversion
ratio (FCR) and deep body temperature (Tb) were measured and distal ileum contents were collected from birds killed by intravenous injection of sodium
pentobarbitone through wing vain, immediately after heat challenge. The assay diet
for second experiment was a nitrogen-free diet to investigate the endogenous protein
and amino acid (AA) output. FCR increased by heat stress (P < 0.05). Heat
acclimation resulted in 20% improvement in FCR in 2wk heat stressed birds as
compare with non-heat acclimated birds (1 wk heat stress) at 3 5-43 days. Tb of both
heat stressed groups increased throughout the heat stress period. 2wk heat stressed
birds had significantly lower Tb than l wk heat stressed birds in day 35 and 37 (P <
0.05), but there was no difference at day 39 (P > 0.05). Crude protein and total
amino acids apparent and true digestibility was significantly depressed by heat stress
(P < 0.05) and this reduction failed to be improved by heat acclimation. Moreover,
the reduction was found in all amino acid except for glutamic acid, aspartic acid,
methionine, tryptophan, serine, alanine and proline. Acclimation and sex had no
effect on total AA availability. Also there was no interaction between sex and heat
challenge duration (P > 0.05). The mean AA availability of soybean meal observed
in the present study was 82% in no-heat stress group and 78% in heat stressed birds.
The relatively low values of AA availability in this study may be attributed to the
soybean meal quality which was suspected to be underprocessed. One of the striking
findings of this study was the low availability value for tyrosine under heat stress
condition (11.9% less than no heat stress) which was the lowest among other AA.
Analysis of endogenous excretion from the second experiment revealed that
glutamic acid, aspartic acid, serine, threonine, leucine and arginine were the
predominant endogenous amino acids present in ileal output. In addition, the lowest
ileal endogenous AA losses were tryptophan, methionine and cystine. |
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