Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The Dorper is numerically the second most abundent of all the sheep breeds in
South Africa. It is the most numerous sheep breed in the dry arid areas of South
Africa which make out a very big portion of the natural grazing in South Africa. In this
study the feedlot performance was specifically investigated since so little research
has been done in this regard. In the first study (Chapter 1), the production efficiency,
body components and commercial yield of 13 Dorper and 12 Merino lambs were
investigated. A pelleted diet was fed ad lib and the water intake per day was
measured. Lambs were slaughtered at 30kg and at 40kg live weight and cut up
according to the South African commercial cuts. The weights of the organs, head,
feet, skin and carcass were also recorded. Results from the first study showed that
Dorpers had a lower (P<0.05) water efficiency (285.97 mVkgO75/day) than the
Merinos (240.07 mVkg075/day), but had a higher (P<0.05) nitrogen retention. The
head, feet, skin, heart, lungs, kidneys and diaphragm of Merino lambs were heavier
(P<0.05). Merinos had heavier (P<0.05) breast and shank and thick rib (only at
40kg live weight) cuts. But the Dorper had a significantly heavier hindquarter
(buttock and loin) which is the high-priced cut of any carcass. It seems that the
Dorper will do well under feedlot conditions, and would possibly make a better
commercial meat producer than the Merino under all circumstances.
In the second study (Chapter 2), the free-ranging Dorper on natural grazing were
compared with 7 Dorper lambs in the feedlot study. The essential amino acids in the
duodenal contents were compared. The free-ranging Dorpers were randomly slaughtered at 40 kg live weight and a duodenal sample was collected. The feedlot
Dorpers were also slaughtered at 40 kg live weight and a duodenal sample was
taken. The second study indicated no significant differences between the EAA
composition of the duodenal samples, whether protein quantity was taken into
account (gAA/100g crude protein (CP)) or not (expressed as % of lysine). The
chemical scores indicated that the two most limiting amino acids in the duodenal
digesta for whole empty body growth were: arginine and histidine. Excess levels of
amino acids tend to be present in all three duodenal digesta samples (isoleucine,
leucine, lusine, methionine, phenylalaline, threonine and valine). The whole empty
body EAA composition (g AA/100 g crude protein) was as follows 7.10 arginine; 2.40
histidine; 3.31 isoleucine; 7.22 leucine; 6.61 lysine; 1.62 methionine; 3.91
phenylalanine; 3.77 threonine and 4.85 valine. The composition can serve as an
example of the ideal EAA requirements for whole empty body growth between 30
and 40 kg live weight of Dorper ram lambs. The duodenal amino acid concentrations
of the free-ranging Dorper compared well with those of the feedlot Dorpers which
suggests that the microbial organisms have a big influence on the amino acid
concentration which reaches the intestines. / AFRIKAANSE OPSOMMING: Die voerkraal prestasie en essentiele aminosuur behoeftes van
groeiende Dorper lammers: The Dorper is getalgewys die tweede mees talryke skaapras in Suid-Afrika. Dit is die
mees talryke skaapras wat in die drce woestynagtige gebiede van Suid-Afrika
aangetref word. Die gebiede beslaan die grootste oppervlakte van Suid-Afrika se
natuurlike weiveld. In die studie is voerkraal prestasie van die Dorper nagevors,
spesifiek omdat daar so min navorsing op hierdie gebied gedoen is. In die eerste
studie (Hoofstuk 1) is die produksie doeltreffendheid, liggaams komponente en
kornrnersiele produksie van 13 Dorper- en 12 Merino lammers ondersoek. 'n
Verpilde rantsoen is ad lib gevoer en die water inname per dag is ook gekontroleer.
Die lammers is geslag op 30 en 40 kg lewende gewig en die karkasse is daarna
opgesny volgens die Suid-Afrikaanse kornmersiele karkassnitte. Die resultate van
die eerste studie het getoon dat Dorpers 'n laer water potentiaal (P<0.05) (285 97
mflkgO 75/dag) as die Merinos (240.07 mVkg075/dag) het. Dorper lammers het ook 'n
hoer (P<0.05) stikstof retensie. Die kop, vel, pote, hart, longe, niere en diafragma
van Merino lammers was swaarder (P<0.05). Merinos se brisket en dikrib snitte
weeg ook swaarder (P<0.05). Die Dorper het 'n beduidende swaarder agterkwart
(len de en boud) gehad, wat die duurste snit is van enige karkas. Die Dorper het baie
goed gedoen in die voerkraal toestande en sal waarskynlik onder aile omstandighede
'n hcer vleisproduksie op die Merino lewer. In die tweede studie (Hoofstuk 2), is die vryweiende Dopers op natuurlike weiding
vergelyk met die Dorpers in 'n voerkraal. Die twee groepe Dorpers se essensiele
aminosuur samestelling in hul dunderms is bepaal en vergelyk om te bepaal of daar
enige tekorte teenwoordig is. Die Dorpers in die veld en in die voerkraal is op 40 kg
lewende gewig geslag en monsters van die dunderm inhoud is gekollekteer. Die
monsters is ontleed om te bepaal of daar enige betekenisvolle verskille in die
essensiele aminosure van die dunderm inhoud tussen die veld Dorpers en voerkraal
Dorpers was. Die tweede studie het geen betekenisvolle verskille getoon tussen die
dunderm monsters se essensiele aminosure, of die hoeveelheid proteien (gAA/100g)
in aanmerking geneem is of nie (uitgedruk as % lisien). Die chemiese telling dui aan
dat die twee mees beperkende aminosure in die dunderm inhoud vir lee liggaam
groei arginien en histidien was. Oormaat vlakke van aminosure kom voor in al drie
dunderm inhoud monsters (isoleusien, leusien, lisien, metionien, femielalanien,
treonien en valien). Die totale lee liggaam essensiele aminosuursamestelling (g
aminosuur/100g ruprotein) was soos volg: 7.10 arginien; 2.40 histidien; 3.31
isoleusien; 7.22 leusien; 6.61 lisien; 1.62 metionien; 3.91 fenielalanien; 3.77 treonien
en 4.85 valien. Hierdie aminosuursamestelling kan as 'n aanduiding dien vir die
ideale aminosuurbehoeftes van Dorper ram lammers vir totale lee liggaamsgroei
vanaf 30 tot 40 kg lewende massa. Die dunderm aminosuur konsentrasie van die
Dorper in die veld stem goed ooreen met die van die voerkraal Dorper. Dit toon
waarskynlik dat die mikrobe organismes in die rumen In groot invloed het op die
aminosuur samestelling wat die dunderm bereik.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52846 |
| Date | 12 1900 |
| Creators | Jurgens, Andre Hendrik |
| 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 | 55 p. |
| Rights | Stellenbosch University |
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