Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The purpose of this study was to determine the essential amino acid requirements of
beef cattle under feedlot conditions through evaluation of the duodenal and whole empty
body essential amino acid compositions. To define the ideal protein required for growth,
the whole empty body essential amino acid compositions of 8 beef steers (Simmental
and Hereford crosses) was investigated. The amino acid composition of the components
(carcass, metabolic organs and residual fraction), was pooled relative to their respective
mass and protein contribution, resulting in the calculated whole empty body amino acid
composition: arginine 6.81; histidine 2.69; isoleucine 4.02; leucine 6.96; lysine 7.43;
methionine 2.01; phenylalanine 4.03; threonine 4.01; valine 5.30; tryptophan 0.82.
Variations in profiles were found between scientific reports, either indicating that ratios
change with growth and implants or possibly through genotype.
The present study's body amino acid ratios were used to estimate dietary amino acid
requirements through evaluation of the duodenal essential amino acid compositions from
three different maize based feedlot diets. Although there was a general increase in the
biological value of protein after rumen fermentation, the duodenal essential amino acids
in comparison with the whole empty body recorded deficient/unbalanced profiles of
essential amino acids for growth. The chemical scores suggested that the first-to-thirdlimiting
amino acids in the duodenal digesta of beef cattle, that received three different
commercially available feedlot diets, were: histidine, lysine, methionine/arginine (Diet 1),
histidine, arginine, lysine (Diet 2) and arginine, methionine, histidine (Diet 3). Thedisproportionate duodenal amino acid concentrations obtained from the three diets,
emphasise the necessity to enhance the intestinal delivery of amino acid profiles through
different undegradable protein sources, with the objective to maximise protein utilisation
and obtain the genetic potential for optimal growth in feedlot cattle.
When amino acid requirements and flows to the duodenum were simulated using the
Cornell Net Carbohydrate and Protein system (CNCPS), predictions indicated that lysine
amino acid flow was limiting the metabolizable allowable average daily gain in Diet 1 and
3. Predicted profiles indicated that the order of limitation was: lysine, arginine, histidine
(Diet 1), lysine, arginine, histidine, methionine (Diet 2) and lysine, arginine, histidine (Diet
3). The predicted profiles were in accordance with observed duodenal values, except for
methionine that was observed limiting in Diet 1 and 3; however, the sequence and extent
of limitation varied. Results indicate that prediction models have potential in predicting
requirements; however there are still limitations for use to accurately define
requirements for particular EAA's.
From the present study, it is clear that the protein accretion was constrained by quantity
and/or disproportionality of amino acids available for absorption. Further research should
therefore be directed towards obtaining a more desirable array of amino acids to the
lower digestive tract that is digestible, absorbable and an economically viable option for
the feedlot operator. / AFRIKAANSE OPSOMMING: Aminosuurbehoeftes van Voerkraalbeeste Volgens die
Duodenale en Totale Lee Liggaam Essensiele Aminosuur
Profiel: Die doel van hierdie studie was om die essensiele aminosuur vereistes van vleisbeeste
onder voerkraal toestande te bepaal deur die evaluering van die duodenale en totale lee
liggaam essensiele aminosuursamesteilings. Om die idea Ie proteiene wat vir groei
benodig word te definieer, is 'n ondersoek ingestel na die totale lee liggaam essensiele
aminosuursamesteilings van 8 vleisbees osse (Simmetailer en Hereford kruise). Die
aminosuursamesteiling van die komponente (karkas, metaboliese organe en residuele
fraksie), se massa en proteien bydrae is gebruik om die totale lee liggaam
aminosuursamestelling 5005 volg te bereken: arginien 6.81; histidien 2.69; isoleusien
4.02; leusien 6.96; lisien 7.43; metionien 2.01; fenielalanien 4.03; treonien 4.01; valien
5.3; triptofaan 0.82. Variasies in profiele tussen wetenskaplike verslae is gevind. Dit dui
daarop dat groei en inplantings of moontlik genotipe 'n invloed op profiele kan he.
Die huidige studie se liggaam aminosuurverhoudings is gebruik om die dieet
aminosuurbehoeftes te skat deur evaluering van die duodenale essensiele
aminosuursamesteilings van drie verskiilende mielie-gebaseerde voerkraal diete.
Alhoewel daar 'n algemene toe name in die biologiese waarde van die proteien na
rumen fermentasie was, het die duodenale essensiele aminosure in vergelyking met die
totale lee liggaam, ongebalanseerde profiele van essensiele aminosure vir groei getoon.
Die chemiese teilings toon aan dat die eerste-tot-derde-beperkende aminosure in die
duodenale inhoud van vleisbeeste wat drie verskillende kommersieel beskikbare
voerkraal diete ontvang het, soos volg is: histidien, lisien, metionieniarginien (Dieet 1), histidien, arginien, lisien (Dieet 2) en arginien, metionien, histidien (Dieet 3). Die
ongebalanseerde aminosuur konsentrasies wat in die duodenum van die drie dlete
verkry is, beklemtoon die noodsaaklikheid om die intestinale lewering van
aminosuurprofiele te verbeter deur verskillende nie-degradeerbare proteien bronne te
voer. Die doelwit moet wees om proteien verbruik te optimaliseer en daardeur die
genetiese potensiaal vir optimale groei in voerkraalbeeste te bereik.
Met die simulering van aminosuurbehoeftes en vloei na die duodenum van die drie
standaard voerkraal diete met behulp van die "Cornell Net Carbohydrate and Protein
System" (CNCPS), het voorspellings gewys dat lisien aminosuurvloei die
metaboliseerbare toelaatbare gemiddelde daaglikse toename in Dieet 1 en 3 beperk het.
Voorspelde profiele wys dat die volgorde van beperking soos volg sou wees: lisien,
arginien, histidien (Dieet 1), lisien, arginien, histidien, metionien (Dieet 2)' en lisien
arginien, histidien (Dieet 3). Die voorspelde profiele was in ooreenstemming met die
waargeneemde duodenale waardes, behalwe vir metionien wat beperkend was in Dieet
1 en 3; die volgorde en mate van beperking was egter verskillend. Resultate wys dat
voorspellingsmodelle die potensiaal het om behoeftes te voorspel. Vir die akkurate
definisie van behoeftes vir spesifieke essensiele aminosuure is daar egter nog
beperkinge.
Uit die huidige studie, is dit duidelik dat protetenneerleqqinq deur die hoeveelheid en/of
oneweredigheid van geabsorbeerde aminosure beperk is. Verdere navorsing moet dus
fokus op die verkryging van In meer geskikte profiel van aminosure wat verteerbaar,
opneembaar en 'n ekonomiese lewensvatbare opsie vir die voerkraalbestuurder is.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52085 |
| Date | 12 1900 |
| Creators | Erasmus, Morné |
| Contributors | Ferreira, A. V., 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 | English |
| Type | Thesis |
| Format | 122 p. |
| Rights | Stellenbosch University |
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