The effect of genotype, drying conditions and microbial enzyme supplementation of the nutritive value of hybrid and open pollinated maize grain for broiler feeding.
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Date
2001
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Abstract
Three experiments were conducted to examine the effects of tannin inclusion in the diet;
heat treatment of maize; and maize genotype and sex of broilers; on the nutritive value of
maize-soyabean based diets, as affected by dietary enzyme supplementation. In
Experiment 1, six hundred day-old Ross male chicks were given 5 main diets. The 5
main diets were based on hybrid yellow maize and a commercial soyabean concentrate
and supplemented with tannin at 0, 5, 15, 20 or 25 g/kg. In addition each diet was either
supplemented with Avizyme 1502 (Finnfeeds International, UK) at 1 g/kg diet, or not.
The birds were given experimental feed from day one to day 22 and the experiment was a
completely randomised design with 5x2 factorial arrangement of treatments, and 6
replicates. The inclusion of tannin in the diet significantly reduced feed intake (P<O.OOO),
weight gain (P<O.OOO) and feed conversion efficiency. The feed conversion efficiency
followed a curvilinear response to dietary tannin level, from a low at the lowest tannin
level, to a peak at tannin level of between 10 and 15 g!kg , whereafter it started declining
with further increase in dietary tannin. Tannin inclusion also significantly reduced the
digestibility of protein (P<O.OI), gross energy (P<0.05), and phosphorus (P<0.05). A
similar trend was seen in terms of ileal digestibility of amino acids. The jejunum tissue
protein was significantly reduced due to tannin inclusion in the diet. The activity of the
digestive enzymes was not significantly affected by tannin inclusion in the diet. Avizyme
1502 supplementation in the diet significantly (P<0.05) improved weight gain of the
birds. There was a non-significant increase in the food intake and feed conversion
efficiency of broilers on diets containing tannin, due to Avizyme 1502 supplementation.
Avizyme 1502 did not have a significant effect on tissue protein content, activity of the
digestive enzymes (except for alkaline phosphatase, of which the activity was
significantly (P<0.05) reduced due to enzyme addition), nutrient digestibility (protein,
gross energy, phosphorus and calcium) and amino acid digestibility in this experiment.
In Experiment 2, three hundred and twenty day-old Ross male chicks were given four
main diets. The four main diets were based on a commercial soyabean concentrate and
hybrid yellow maize that was sun-dried (control) or oven-dried at temperatures of 85°C,
95°C or 105°C. The oven-dried maize were dried for 24 hours. Each diet was in addition
either supplemented with Avizyme 1502 at 1 g/kg diet, or was left without the Avizyme
supplement. The birds were given experimental feed from day one to day 28 and the
experiment was a completely randomised design with 4x2 factorial arrangement of
treatments, and six replicates. Heat treatment of maize significantly (P<0.05) improved
food intake and feed conversion efficiency. Above a drying temperature of 95°C, heat
negatively affected these variables. The digestibility of phosphorus and calcium were
also improved by heat treatment of maize. Heat did not have an effect on the activity of
the digestive enzymes, tissue protein and amino acid digestibility (threonine , methionine,
lysine and phenylalanine). Avizyme 1502 supplementation significantly (P<0.05)
improved weight gain, sucrase activity and the jejunum protein. Its addition did not have
a significant effect on nutrient digestibility (protein, gross energy, phosphorus and
calcium), activity of the rest of the digestive enzymes and the digestibility of amino acids.
In Experiment 3, two hundred and forty day-old Ross male chicks were reared separately
in this study. Chicks were allocated to battery cages and assigned to one of the dietary
treatments. The two main diets were based on a commercial soyabean concentrate and
hybrid yellow maize or open pollinated maize respectively. The open pollinated maize
was grown in the northern part of KwaZulu-Natal (Hlabisa). Each diet was in addition
supplemented with Avizyme 1502 at 1 g/kg diet. The birds were given experimental feed
from day one to day 21 and the experiment was a completely randomised design with
2x2x2 factorial arrangement of treatments, and 6 replicates. Maize type used and sex of
birds had no significant effect on chicken performance, nutrient digestibility, activity of
digestive enzymes and amino acid digestibility (threonine, methionine, lysine and
phenylalanine). Although it was not statistically analysed, the chemical composition of
the two maize varieties suggested that open pollinated has a more concentrated nutrient
and energy content than hybrid maize. This suggests that rural people can be encouraged
to continue feeding open pollinated maize to their chickens, and to continue conserving
this plant genetic resource.
Description
Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2001.
Keywords
Feeds--Composition., Broilers (Chickens)--Feeding and feeds., Broilers (Chickens)--Nutrition., Poultry--Feeding and feeds., Corn as feed., Enzymes in animal nutrition., Theses--Animal and poultry science.