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| Articles
by
J. T. Halley |
Total Records (
1 ) for
J. T. Halley |
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Cesar Coto
,
F. Yan
,
S. Cerrate
,
Z. Wang
,
P. Sacakli
,
P.W. Waldroup
,
J. T. Halley
,
C.J. Wiernusz
and
A. Martinez
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A study was conducted to evaluate the effects of dietary levels of calcium, nonphytate
P (NPP), phytase and 25-hydroxycholecalciferol (25-OH) on live performance and
bone development in male chicks fed a wheat-based diet. Dietary treatments consisted
of a 2 x 2 x 4 x 4 factorial arrangements with two levels of supplemental phytase
(0 or 1200 FTU/kg), two levels of 25-OH (0 or 69 µg/kg), four levels of
calcium (0.20% less than a 2:1 ratio of Ca to NPP; 2:1 ratio of Ca to NPP; 0.20%
Ca greater than a 2:1 ratio of Ca to NPP; 0.40% Ca greater than a 2:1 ratio of
Ca to NPP) and four levels of NPP (0.35, 0.40, 0.45 and 0.50%) for a total of
64 treatments. The primary basal diet used to mix all experimental diets was supplemented
with a complete vitamin mix containing 5500 IU of cholecalciferol. Each diet was
fed to two pens of six male chicks of a commercial broiler strain in electrically
heated battery brooders for three consecutive trials using the same diet mix for
a total of six replicates per treatment. At 18 d birds were weighed, feed consumption
determined and all birds killed for bone measurements. Toes from all birds within
a pen were removed and ashed. Tibiae from both legs were removed and scored for
incidence and severity of tibial dyschondroplasia and for incidence of calcium
or phosphorus rickets. Ca: NPP ratios and calcium levels similar or higher than
NRC (1994) recommendations appear necessary for adequate bird performance. Phytase
supplementation improved performance parameters such as FCR and body weight, whereas
the addition of 25-OH to diets already containing 5500 IU/kg of cholecalciferol
had a negative effect on FCR due to a possible hypercalcemia condition. Bone development
was improved by increasing phosphorus and calcium levels. Moreover, supplementation
with 25-OH and its combination with phytase were effective in enhancing bone development.
Increasing Ca levels consistently reduced leg abnormalities. Addition of 25-OH
helped to relieve leg problems when suboptimal calcium levels were supplied while
phytase supplementation was effective for this purpose when high Ca levels were
given. The addition of these additives could be seen as an strategy to alleviate
problems with suboptimal Ca: NPP ratios. |
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