Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The aim of this study was to determine whether a lamb finishing ration that is
balanced for essential amino acids (EAA), at a specific level of non-structural
carbohydrates (NSC) would yield better feedlot performance when compared to a
standard commercial finishing ration.
Metionine (Met) and Lysine (Lys) were identified as the first limiting amino acids for
growing lambs. These two amino acids, as well as Threonine (Thr), Arginine (Arg),
Leucine (Leu), Isoleucine (Ile) and Phenylalanine (Phe) were included in an
optimized protein (OP) feedlot ration at optimal levels. This ration was formulated to
contain 157 g/kg crude protein (CP) and 477 g/kg NSC, with Met, Lys, Arg and Thr at
2.48, 7.45, 8.51 and 8.12 g/kg on dry matter (DM) basis respectively. The second
treatment, FIN, was a standard commercial lamb finishing feed without optimized
amino acids and contained similar total protein and NSC to OP of 152 g/kg CP and
468 g/kg NSC but with Met, Lys, Arg and Thr at 2.08, 5.49, 7.47 and 4.80 g/kg on
DM basis respectively. A third treatment, a low protein (LP) diet served as a positive
control and was formulated on lower specifications (139 g/kg CP, 455 g/kg NSC) and
was also not optimized for amino acids. This treatment contained Met, Lys, Arg and
Thr at 1.93, 4.99, 6.66 and 4.73 g/kg on DM basis respectively. Lambs grazing
kikuyu pasture served as the negative control (CON) group. These lambs also
received additional supplementary feed at 500 g/day as a production lick to be
comparable to a scenario where lambs are finished on grazing. Forty cross-bred Merino x Döhne-Merino lambs with an average weaning weight of
24.35 ± 0.648 kg were finished in a feedlot for 57 days where after they were
slaughtered at an average weight of 41.41 ± 1.259 kg. During the feedlot trial lamb
performance was measured by monitoring daily growth rates and feed intake. Also,
an in vivo digestibility study was carried out on the OP and FIN lambs. During the
slaughter process the rumen was removed which was done to collect a sample of
the rumen wall from next to the rumino-reticular fold. These rumen samples were
mounted onto slides so that the development of the rumen could be examined. The M. longissimus dorsi from both sides of the carcass between the 2nd and 3rd last
thoracic vertebra and the 4th and 5th lumbar vertebra were removed.
There was no significant difference (P > 0.05) between any of the concentrate feed
treatments with regards to the average daily gain (ADG), feed conversion ratio (FCR)
or dressing percentage (DP). The CON lambs, as expected, had lower growth rates
(P < 0.05) than the concentrate fed lamb and thus showed significant differences (P
< 0.05) in terms of ADG. The DP of 45.96 % ± 0.711 for the CON lambs differed
significantly (P < 0.05) from the OP (51.44 % ± 0.358), FIN (52.72 % ± 0.653) and LP
(51.74 % ± 0.611) treatments. As expected the concentrate feeds were much more
effective in maintaining higher growth rates when compared to the CON lambs while
the optimizing of EAA in the OP diet did not lead to improved feedlot performance as
the FIN and LP treatments were able to achieve similar (P > 0.05) growth rates.
Within the feedlot treatments there was no significant difference (P > 0.05) with
regard to the papillae length and rumen wall thickness. There was however a
numerical increase in the papillae length as the NSC levels in the feed increased.
The CON lambs differed from the OP lambs (P < 0.05) in terms of papillae length.
This illustrated the importance of having increased levels of NSC in a feedlot diet as
it is this fraction that is responsible for the initialisation and maintenance of rumen
morphological development. The in vivo digestibility study therefore confirmed that the commercial finishing feed
was just as effective as the optimized feed in terms of nitrogen retention as well as in
maintaining suitable energy balance. Although the in vivo digestibility for Met and Lys
in the OP feed was higher (P < 0.05) than the FIN feed, this did not lead to improved
feedlot performance of the OP lambs. The increased digestibility of these amino
acids is due to the fact that the OP diet was higher in levels of bypass amino acids
than the FIN feed. The in vitro true digestibility (IVTD) of the OP feed was higher (P < 0.05) than that of the FIN feed. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om te bepaal of ‘n lamafrond rantsoen wat
gebalanseerd is vir beperkende essiensiële aminosure (EAA) teen ‘n spesifieke vlak
van nie-strukturele koolhidrate (NSK) beter voerkraal prestasie teweeg sou bring
wanneer gemeet word teen ‘n standaard kommersiële afrond rantsoen.
Metionien (Met) en Lisien (Lis) is geïdentifiseer as die eerste beperkende aminosure
vir groeiende lammers. Hierdie twee aminosure, asook Treonien (Tre), Leusien
(Leu), Isoleusien (Ile) en Fenielalanien (Fen) is teen optimale vlakke ingesluit in ‘n
geoptimeerde voerkraal rantsoen, OP. Hierdie rantsoen is geformuleer om 157 g/kg
RP en 477 g/kg NSK te bevat asook Met, Lis, Arg en Tre teen 2.48, 7.45, 8.51 en
8.12 g/kg onderskeidelik. Die tweede behandeling, FIN, was ‘n kommersiële
lamafrond voer waarin die aminosure nie geoptimeer is nie en het soortgelyke vlakke
van proteïene en NSK bevat teen 152 g/kg RP en 468 g/kg NSK met Met, Lis, Arg
en Tre teen 2.08, 5.49, 7.47, 4.80 g/kg onderskeidelik. ‘n Derde voer, LP, het gedien
as ‘n positiewe kontrole en was ‘n lae proteïen voer met laer spesifikasies (139 g/kg
RP, 455 g/kg NSK) waarin die aminosure ook nie geoptimeer is nie. Die LP voer het
Met, Lis, Arg en Tre bevat teen 1.93, 4.99, 6.66 en 4.73 g/kg onderskeidelik. Die
negatiewe kontrole behandeling, CON, is verteenwoordig deur lammers wat op
kikuyu gewei het terwyl addisionele supplementêre voeding teen 500g/lam/dag
voorsien is. Hierdie supplementêre voeding het gedien as ‘n produksie lek om
sodoende vergelykbaar te wees met scenario waar lammers op weiding afgerond word. Veertig kruisgeteelde Merino x Döhne-Merino lammers met ‘n gemiddelde gewig van
24.35 ± 0.648 kg is vir 57 dae in ‘n voerkraal afgerond waarna hulle, teen ‘n
gemiddelde gewig van 41.41 ± 1.259 kg, geslag is. Tydens die voerkraal proef is
prestasie gemonitor deur die meet van daaglikse groei en voerinname. Hiertydens is
daar ook ‘n in vivo verteringsproef op die OP en FIN lammers gedoen. Tydens die
slagproses is die rumen verwyder waarna ‘n monster van die rumenwand langs die
rumino retikulêre vou geneem is. Hierdie rumenmonsters is op skyfies geplaas sodat
die ontwikkeling van die rumen ondersoek kan word. Die M. longissimus dorsi was aan beide kante van die karkas tussen die 2de en 3de laaste torakale werwels en
die 4de en 5de lumbale werwels verwyder.
Daar was geen betekenisvolle verskille (P > 0.05) tussen enige van die konsentraat
behandelings ten opsigte van gemiddelde daaglikse toename (GDT), voeromset
verhouding (VOV) of uitslag persentasie nie. Die CON lammers het egter, soos
verwag, beduidend (P < 0.05) stadiger gegroei en het dus verskille getoon ten
opsigte van GDT. Die uitslag persentasie van 45.96 % ± 0.711 vir die CON lammers
het ook betekenisvol verskil (P < 0.05) van die OP (51.44 % ± 0.358), FIN (52.72 %
± 0.653) en LP (51.74 % ± 0.611) behandelings.
Binne die voerkraal behandelings was daar geen betekenisvolle verskille (P > 0.05)
ten opsigte van die papillae lengte en rumenwand dikte nie, alhoewel daar ‘n
numeriese toename in papillae lengte was soos die NSK vlakke in die voer gestyg
het. Die CON lammers het wel van die OP lammers verskil (P < 0.05) ten opsigte
van papillae lengte. Hierdie bevinding het bevestig hoe belangrik NSK is in die
inisiasie en instandhouding van die morfologiese ontwikkeling van die rumen. Die in vivo verterings studie het daarop gedui dat die kommersiële afrond voer net so
effektief soos die geoptimeerde voer was in terme van stikstof retensie asook die
handhawing van ‘n geskikte energie balans. Alhoewel die in vivo verteerbaarheid
van Met en Lis in die OP hoër was (P < 0.05) as in die FIN voer, het hierdie verskille
nie gelei tot beter groei in die OP lammers nie. Hierdie verskil in verteerbaarheid is
toegeskryf aan die feit dat die aminosure in die OP voer meer rumen-beskermd was
as dié in die FIN voer. Die in vitro verteringstudie het daarop gedui dat die OP voer
beduidend beter (P < 0.05) verteer is as die FIN voer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86257 |
| Date | 04 1900 |
| Creators | Moolman, Justin |
| Contributors | Van De Vyver, W. F. J., Hoffman, L. C., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xviii, 111 p. : ill. |
| Rights | Stellenbosch University |
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