1. A study was conducted to investigate the effects of dietary Ca levels and feed
restriction on the bone development of broiler breeder pullets up to 18 weeks of age.
Six hundred and forty one-day-old Ross breeder pullets were randomly assigned to 4
treatment groups; namely 1.0% Ca (0.45% Pi), 1.5% Ca (0.7% Pi), 2.0% Ca (0.9%
Pi) and 1.0% Ca (0.45% Pi). The first three treatments were feed restricted while the
last treatment was fed ad lib. At 6, 12 and 18 weeks of age 20 pullets were randomly
selected from each treatment and killed. Treatment effects on bone dimensions
(length, width and weight), bone ash, Ca and P contents of tibia, mechanical
properties (bone strength and stress) were investigated. Increasing dieta ry Ca levels
had no significant (P>0.05) effect on bone measurements. As expected, all the bone
measurements significantly (P<0.05) increased with age. Feed restriction significantly
(P<0.05) reduced all the bone characteristics. The results suggested that 1.0% Ca
(average 0.7 g/hen/day) is sufficient to support bone development and growth for feed
restricted broiler breeder pullets up to 18 weeks of age.
2. One hundred and ninety eight Ross broiler breeder pullets were reared on
restricted diets with 1.0, 1.5 and 2.0% Ca up to 22 weeks of age. The pullets in each
experimental diet were further randomly divided into three treatments with 1.5, 2.5
and 3.5% dietary Ca (66 birds per treatment) fed from 23 to 60 weeks. At 35 and 60
weeks of age, 12 pullets per treatment were randomly selected and killed to obtain
tibiae and humeri. Treatment effects on bone dimensions, bone ash, Ca and P content
of tibia, mechanical properties, true cortical area (TCA) and percent bone were
investigated. The 1.5% Ca diet resulte d in lower (P<.05) feed intake and body weight.
Calcium level had no effect on bone dimensions, bone stress, ash content, Ca content
of ash, TCA and percent bone. These results suggest that the 2.5% dietary Ca (4
g/hen/day) may be adequate to support bone development and growth of feed
restricted broiler breeder pullets.
3. The broiler breeder pullets described in paragraph 2 were used to investigate the
effects of three levels of dietary Ca (1.5, 2.5 and 3.5%) during the early lay period (23
to 35 weeks) on egg production and eggshell quality. Increasing dietary Ca level from
1.5 to 3.5% had no significant effect (P>.05) on egg production, egg weight, egg
mass, egg surface area and egg contents. Increasing the level of Ca from 1.5 to 2.5% increased shell weight, shell weight per unit surface area, shell percentage and shell
thickness. As anticipated, egg weight increased with age. The converse was true for
egg production and eggshell parameters. It was concluded that a dietary Ca level of
2.5% and Ca intakes of 3.8, 3.9, and 3.5 g at weeks 27, 30 and 33, respectively were
sufficient to sustain good eggshell quality of feed restricted broiler breeder hens.
4. The mentioned broiler breeder hens in paragraph 3 were fed three dietary Ca
levels, 1.5, 2.5 and 3.5% from week 36 to 60. Regression analysis suggested that Ca
level during the rearing period could positively influence eggshell quality during the
later stages of lay (36 to 60 weeks). Increasing dietary Ca level from 1.5 to 2.5%
during the laying period significantly (P<.05) increased egg production, egg weight,
egg mass, shell weight, egg contents, egg surface area, shell percentage, shell weight
per unit surface area and shell thickness. As anticipated, egg weight, shell weight, egg
contents and egg surface area increased with age while egg production, egg mass,
shell percentage and shell thickness declined. These results suggest that the 2.5% Ca
(3.8 g/hen/day) is adequate to support egg production and to improve eggshell quality
in feed restricted broiler breeder hens.
5. The effect of dietary Ca intake (1.5, 2.5 and 3.5% dietary Ca) on Ca retention of
broiler breeder hens (30 per treatment) and the relationship between Ca retention and
egg characteristics was investigated. Shell (r=0.27) and faecal (r=0.50) Ca excretions
were significantly (P<.05) positively related to Ca intake of broiler breeders.
Proportionally less of the Ca intake was used for eggshell formation as the intake of
broiler breeders increased. It seems that a higher Ca intake was mainly accompanied
by a higher Ca excretion through the faeces. The net effect of Ca intake and total Ca
excretion was that the 2.5% Ca level (3.8 g Ca /hen/day) exhibit a significant (P<.05)
higher Ca retention compared to 1.5% Ca.
It was concluded from the results that 1.0% dietary Ca (0.7 g /pullet/day) is needed
during the rearing period up to 22 weeks. Thereafter 2.5% Ca (3.5 to 4.0 g /hen/day)
should be included in broiler breeder diets up to 60 weeks. The possible effect of Ca
levels during the rearing period on eggshell quality needs further investigation.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-11102005-082027 |
| Date | 10 November 2005 |
| Creators | Moreki, John Cassius |
| Contributors | Prof HJ van der Merwe |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-11102005-082027/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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