Influence of composition and storage conditions on diet quality and productivity of broiler chickens.
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Date
2003
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Abstract
Two experiments were conducted to assess the effects of varying storage temperature
and relative humidity (RH) on feed quality and nutritive value of such diets when fed
to broiler chickens. The diets used in experiment two were higher in lipids than those
used in experiment one. All other features of the diets tested lin the two experiments
were identical. Diets were also supplemented with or without inhibitor during storage.
Prior to feeding, the diets were also supplemented with or without a fungal detoxifier.
Laboratory analysis showed that the diets contained Aspergillus spp, Penicillium spp
and Fusarium spp with no toxins identified. Storage at high temperature (30°C) over
one month increased dry matter (DM) content by about 1%, which was accompanied,
by an increase of between 3.5-5% in crude protein (CP) as well as 3-4% fat
(Experiments One and Two). After two months of storage, high storage temperature
decreased DM content by about 1.6%, which resulted in a decrease in the levels of CP
and fat in most of the diets (Exp. One). In experiment two, an increase of about 0.5%
in the DM content was observed in diets stored at low temperature (15°C) followed by
an increase of about 3% in fat content. Variable changes were observed in the micromineral
contents. In experiment one, there was an increase in Fe and Zn content after
one month, followed by variable decreases in the second month, while in experiment
two, there was a decline in the concentrations of Fe, Zn and Cu by about 21, 16 and
26%, respectively throughout the storage period.
Rancidity developed with time in all the diets but there was a tremendous reduction
(p<0.001) in the rate of oxidation by 15% and 20% with supplemental inhibitor
(antioxidant) in experiment one and two, respectively but no reduction in free fatty
acid (FFA) content. High storage temperature (30°C) and RH (80%) increased FFA
content from 3.5 to about 15% in experiment one (p<O.OOl, R2
= 0.73) and to about
17% in experiment two (p<0.001, R2 = 0.84) during the storage period of 60 days.
Storage at low temperature (l5°C) and RH (50%) similarly decreased peroxide value
(Pv) by about 16% in experiment one (p<O.OOl, R2 = 0.84) and in experiment two by
25% (p<0.001, R2 = 0.89) over time. Inclusion of the antioxidant decreased the
concentration of Pv by about 10% in experiment one (p<O.OOl) and by 20% in
experiment two (p<0.001).
Feed intake of birds was unaffected. Storage temperature did not influence body
weight (Experiment one) but in experiment two, high feed storage temperature
decreased (p<0.001) body weight by about 3%. Supplementation of diets with the
inhibitor improved (p<0.001) body weight only in experiment two. Further
supplementation with the detoxifier markedly improved (p<0.01) body weight in both
experiments. Low RH increased feed conversion efficiency (FCE) by 6% in
experiment one (p<O.OOl) and in experiment two (p<0.01). Improvements (p<0.05) in
FCE were observed on diets stored at low temperature in experiment one and with
further supplemental detoxifier, (p<O.Ol). No significant differences were noticeable
in body weight or in FCE in experiment two. Mortality was unaffected by treatments.
The relative liver weight of birds was markedly reduced as a result of low storage
temperature and RH. Dietary supplemental inhibitor or detoxifier reduced (p<0.001)
liver weight between 8 and 10% in both experiments. On the other hand, heart weight
was unaffected by storage conditions. However, in experiments one and two, the
detoxifier caused a reduction (p<O.OOl) of 11% in heart weight unlike the inhibitor.
Proventriculus weight was reduced (p<0.05) by feeding diets stored at low RH in
experiment one by 4%, while no effects were observed in experiment two. Both
studies showed no changes in the proventriculus weight when the inhibitor and
detoxifier were added. Storage at low temperature and RH in experiment one caused a
significant decrease (p<0.01) of 4% gizzard weight unlike in experiment two. The
inhibitor reduced gizzard weight by about 7% in experiment one (p<0.001) and
experiment two (p<0.05). Further supplemental detoxifier decreased gizzard weight in
experiment one (p<0.01) and two by 6% (p<0.001). Spleen weight was not affected
by any of the treatments except in experiment one, where the weight of the spleen was
reduced (p<0.05) by detoxifier from 0.13- 0.12g/100g body weight (7.7%).
Storage conditions did not affect the biochemistry of serum obtained from the chicks
in experiment one, while in experiment two, high temperature decreased (p<0.05)
total phosphorus from 3.4-2.9 mmoVI and high RH decreased (p<0.05) serum protein
(3.3-3.1g/100ml) as well as globulin (1.74-1.58g/100ml). Supplemental inhibitor
increased serum protein (p<0.05)' by 6% and globulin (p<0.01) by about 12%
(experiment one) and albumin (p<0.05) by 7% (experiment two). Further
supplementation with the detoxifier increased (p<O.OOl) phosphorus by about 3.5%
(experiment one), while in the second experiment, serum phosphorus and albumin
were increased (p<0.05). No signs of 'rubbery' bones were observed in birds in these
studies. Furthermore, there were no observable changes as a result of storage
conditions or addition of inhibitor in diets. However, it was observed that
supplemental detoxifier increased bone ash from an average of 51.2 to 51.8% in
experiment one and in experiment two, 50.6-52.5%.
The results of the studies indicated a development of feed contamination (quality loss)
over time with tremendous rate of increase observed in diets devoid of the
preservatives (antioxidant and mold inhibitor). Further supplementation of the
detoxifier markedly improved productivity as well as some of the serum biochemical
parameters measured.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.
Keywords
Broilers (Chickens)--Nutrition., Broilers (Chickens)--Feeding and feeds., Poultry--Feeding and feeds., Theses--Animal and poultry science.