Assignment (MPhil)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of this study was to evaluate the performance and profitability of different dietary specifications for
broiler chickens slaughtered at 35 days of age. Two trials were performed to evaluate different production
parameters. The results of these trials were compared to the predicted results of the EFG broiler model. No
carcass data were available for the two trials mentioned above. Therefore, in order to evaluate the accuracy
of the broiler model when predicting carcass characteristics, two published data sets (Leeson et al., 1996a)
were used. Predicted and actual values were compared, evaluated and discussed.
Two broiler trials were performed. In Trial One the amino acid density decreased throughout the range of
three treatments from prestarter to finisher diets. In Trial Two the amino acid density decreased only in the
four finisher diets. The main difference between predicted and actual results was the response to body
weight. The model predicted a steady increase in feed intake to compensate for the lower dietary
specifications while body weight did not change significantly. This increase in feed intake seems to be
enough to maintain body weight. Trial birds also increased their feed intake as dietary amino acid density
decreased, but this compensation seemed to be too low to maintain body weight compared to the control diet.
The birds may find it easier to compensate when they have time to adapt to the specification.
There is evidence in the literature that birds need seven days to adapt their feed intake to a lower feed
specification (Leeson et al., 1996a). It can be speculated that the trial birds started to loose body weight due
to a lower amino acid intake in this period. The model seems to adapt feed intake immediately after a
change in diet specification.
The simulation on literature data lead to the following conclusions:
1) Broilers posses the capacity to increase their feed intake with at least 65% should finisher diets with
lower amino acid and energy concentrations be supplied. If only the energy concentration of finisher
diets were decreased, the increase in feed intake will be around 30%. (see Table 16 and 23)
2) The accurate prediction of feed intake from the given dietary specification has a major influence on
the accuracy of the prediction of broiler performance.
3) Amino acid density and DLys:ME ratio plays a significant role in the control and prediction of feed
intake.
The EFG broiler model is based on sound scientific principles. The model is comprehensive and can be
used for a wide range of environmental and management conditions as well as dietary conditions. The
nutritionist can use the model with confidence to assist in practical feed formulation. The actual strength of
the model lies in the time and money being saved compared to practical trials. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om die prestasie en winsgewendheid van braaikuikens te bepaal wanneer voere
met verskillende digthede tot op 35 dae gevoer word. Twee eksperimente is uitgevoer om produksieresultate
te evalueer. Die resultate van hierdie eksperimente is met die voorspelde waardes uit die EFG
simulasie-model vergelyk. Aangesien geen karkasdata vir bogenoemde eksperimente beskikbaar was nie, is
twee gepubliseerde datastelle gebruik om hierdie deel van die model te evalueer (Leeson et al., 1996a).
Twee braaikuiken eksperimente is uitgevoer. Eksperiment Een het uit drie behandelings bestaan waarvan die
aminosuur-konsentrasie vanaf dag een tussen behandelings verskil het. In Eksperiment Twee het die
aminosuur-konsentrasie net in die vier afrondingsdiëte verskil. Liggaamsmassa op 35 dae het die grooste
verskil tussen voorspelde- en werklike waardes getoon. Beide voorspelde en werklike innames het in albei
eksperimente verhoog soos wat aminosuur-konsentrasie afgeneem het. Voorspelde liggaamsmassa het egter
konstant gebly terwyl werklike data 'n afname in liggaamsmassa getoon het. Dit bleik dat die voorspelde
toename in innames voldoende was om massa te onderhou terwyl die voëls in werklikheid nie genoeg
gekompenseer het nie. Leeson et al., 1996a het tot die gevolgtrekking gekom dat braaikuikens minstens
sewe dae benodig om hul voeriname by 'n nuwe spesifikasie aan te pas. So 'n stadige aanpassing kan
daartoe lei dat energie- en aminosuur-inname daal indien 'n dieet met laer spesifikasie gevoer. Dit sal
daartoe lei dat die kuikens liggaamsmassa verloor.
Uit die literatuur simulasies is die volgende afleidings gemaak:
1) Braaikuikens besit die vermoeë om voerinname in die afrondingstyd met minstens 65% te verhoog
indien 'n afrondingvoer met laer amiosuur- asook energiekonsentrasie gevoer word. Indien net die
energiekonsentrasie verlaag word, sal die inname met sowat 30% verhoog.
2) Die akkurate voorspelling van inname is krities vir die akkurate voorspelling van produksieparameters.
3) Aminosuur-digtheid en DLys:ME speel 'n belangrike rol in die beheer en voorspelling van
voerinname by braaikuikens.
Die EFG braaikuikenmodel is op suiwer wetenskaplike beginsels geskoei. Die model is omvattend en kan
vir 'n wye reeks van omgewings- en bestuurstoestande asook dieet-spesifikasies gebruik word. Die
voedingkundige kan die model met vertroue gebruik om met praktiese voerformulering by te staan. Die
model kan die formuleerder baie tyd spaar aangesien praktiese eksperimente ingeperk kan word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49817 |
| Date | 03 1900 |
| Creators | Van Niekerk, S. J. (Sarel Johannes) |
| Contributors | Ekermans, L. G., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 94 p. : ill. |
| Rights | Stellenbosch University |
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