Evaluating the efficacy of exogenous composite microbial enzymes in maize-soybean based broiler chicken feeds.
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Date
2006
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Abstract
This research reported here was carried out to examine alternatives to antibiotic growth
promoters as a result of their being banned in the animal feed industry. Four experiments
were conducted to evaluate the efficacy of non-medicated feed additives as replacements
for antibiotic growth promoters in broiler feeds. The additives used were enzymes (a new
thermo-tolerant powder enzyme called TXAP, phytase, lipase and a new phytase enzyme
derived from E. coli called phyzyme XP), organic acid (Acid Pak), prebiotic (Bio-MosĀ®)
and probiotic (All-Lac XCL). Mashed maize-soya based feeds were used in all the
experiments, which were conducted in litter-floor pens.
The first experiment was a dose-response trial. Broilers in eight replicate pens of 50 males
and 50 females were fed unsupplemented feeds and five additional feeds containing
increasing levels of TXAP, from 0.5 to 2.5 g/kg to 42 d. The second experiment used
enzyme TXAP with two different enzymes (phytase and lipase), individually or in
combination. Six replicate pens of 50 males and 50 females were fed either
unsupplemented feeds or one of six additional feeds treated with TXAP, lipase, phytase , a
combination of TXAP and lipase, a combination of TXAP and phytase or a combination
of all the three enzymes . This trial continued for 42 d.
In the third experiment three types of TXAP (Lot 1, 2 and 3) were used, with fixed levels
of xylanase and amylase but varying levels of protease activities (4000, 2000 and 1000
U/kg for Lot 1, 2 and 3, respectively) in combination with phyzyme XP for 35 d. The
fourth experiment used mannan-oligosaccharide (Bio-MosĀ®), organic acid (Acid pak 2x),
probiotic (All Lac XCL 5x), individually or in combination and an antibiotic growth
promoter (Zinc bacitracin) for 42 d. The chickens in this experiment were challenged with
Clostridium perfringens (CP) at 21, 22 and 23 d to determine the efficacy of these
additives for replacing antibiotics in hindering the effects of CP on the villus surface area.
The dose-response trial did not show any significant improvement in broiler performance
with any level of inclusion of enzyme TXAP. The results from this study showed some
beneficial effects with the use of enzyme TXAP when fed alone and at a young age. Its
use when combined with other enzymes and at later stages of growth needs further
investigation. Feed additives in experiment 4 prevented the negative effects of CP as the
treated chickens did not have lesions on their villus surfaces.
The conditions under which these trials were conducted appeared to be such that little
benefit was derived from the use of any of the feed additives used. It is possible that under
less-hygienic conditions such as those in commercial operations greater benefits from
these additives may be realised.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
Keywords
Poultry--Feeding and feeds., Chickens--Feeding and feeds., Broilers (Chickens)--Feeding and feeds, Growth promoting substances., Feed additives., Feeds--Composition., Enzymes in animal nutrition., Antibiotics in animal nutrition., Broilers (Chickens)--Growth., Poultry--Feed utilization efficiency., Theses--Animal and poultry science.