PhD

A 4 x 4 factorial arrangement to determine the dietary
requirements of calcium and phosphorus for caged layers under the
hot-humid agro-climatic conditions of Kerala is presented in this thesis.
Two hundred fifty six single comb White leghorn strain cross
pullets (IWN x IWP ) of the Mannuthy Centre of AICRP on Poultry
foe eggs formed the experimental birds. The birds were randomly
assigned to 16 dietary calcium-phosphorus combination groups. The
dietary calcium levels employed were 2.50, 3.00, 3.50 and 4.00 per cent
and that of phosphorus levels wee 0.50 , 0.60, 0.70 and 0.80 percent
the observations of the experiment were recorded over 10,28 day –
periods
The percent hen-day egg production and feed efficiency (both
on egg number and egg mass) were significantly (P < 0.01) superior in
birds fed 4.00 percent dietary calcium.
The dietary levels of
phosphorus had not exerted any influence on hen-day egg production
and feed efficiency.
The feed intake and egg weight were not
influenced either by the dietary levels of calcium or phosphorus or
both. The egg shell quality (specific gravity and shell thickness ) was
significantly (P < 0.01 ) better in egg laid by hens fed 3.50 and 4.00
percent dietary calcium.
The percent egg shell was significantly (p< 0.01) highest with 3.50
percent calcium. However, percent egg shell between 3.50 and 4.00
percent dietary calcium was not statistically different. The egg shell
quality (specific gravity, shell thickness and percent shell) was
significantly (P< 0.01) poorest with 2.50 percent calcium diet. The
dietary phosphorus levels had not exerted any significant influence on
egg shell quality (specific gravity, shell thickness and percent shell).
The serum
calcium level, serum inorganic phosphorus level and
percent tibia ash were not influenced by the levels of dietary calcium
and phosphorus . The serum alkaline and acid phosphatase levels did
not give any clue as to the adequacy of the dietary calcium and
phosphorus level employed.
The calcium intake was higher with
higher levels of dietary calcium.
There was a trend of increased
absolute calcium retention as the calcium level in the diets increased
but it was not statistically significant.
Dietary phosphorus levels
positively improved absolute retention calcium. The mortality among
birds were nit suggestive of any influence due to dietary calcium and
phosphorus.
The results of experiments revealed that in terms of any of the
major economic traits used for evaluating the dietary calcium
adequacy of caged layers, 4.00 percent calcium was found to be
superior over the other levels.
In respect of dietary phosphorus, the levels of 0.50 per cent seems to be
adequate but the absolute retention of phosphorus was negative at
this level of incorporation irrespective of calcium levels. Therefore, it
will be more logical to set the requirements of dietary phosphorus at
0.60 per cent than at 0.50