Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / Video 1: Twin-bearing Döhne Merino ewe butting only one of her lambs in typical rejection behavior. Rejection of one twin is not a common phenomenon. (Video by Dr Marlize Viviers) / Video 2: Twin-bearing ewe # 22 accepting alien lamb # 179. The alien lamb wears a jacket her other lamb has been wearing for the preceding 24 hours. The excessive sniffing at the jacket, bleating and looking around show that the ewe is not totally satisfied with the situation. (Video by Dr Marlize Viviers) / Video 3: Ewe # 22 rejecting alien lamb # 179 after removal of the jacket it has worn in the previous video. (Video by Dr Marlize Viviers) / ENGLISH ABSTRACT:
Sheep husbandry substantially contributes to South Africa’s economy. Lamb
mortality is regarded as a major constraint to sustainable sheep production, and an
important factor in lamb survival is the strong ewe–lamb bonding. This is a well-known
phenomenon in all sheep races and strong evidence exists that the selective ewe–lamb
bond formation has a pheromonal basis, in that the ewe can distinguish her lamb by its
unique, familiar smell. Sheep farmers and scientists have examined various methods of
making alien lambs acceptable to foster ewes. The survival rate of offspring could be
substantially increased if a reliable method could be devised to prevent ewes from
rejecting their own lambs or if ewes could be induced to accept alien lambs. A better
understanding of the semiochemicals involved in this communication between ewe and
offspring could facilitate the development of a method by which ewes can be coaxed into
adopting foster lambs. This would positively contribute to efficient sheep production in
South Africa.
The objective of this study was to characterise the volatile constituents present in
the wool and the amniotic fluid collected from the Döhne Merino lambs to achieve a
better understanding of the ewe–lamb semiochemical communication. The volatile
organic constituents associated with the wool and amniotic fluid were characterised and a
total of 133 volatile organic compounds were identified. Several compound classes are
represented in these samples and the majority of these compounds have previously been
identified in the excretions and secretions of numerous mammalian species.
A number of different aspects of ewe–lamb kin recognition were investigated.
First, the odour profiles of twin lambs were compared to those of other twins. The results
of these analyses revealed that the wool volatiles of twin lambs are qualitatively as well
as quantitatively practically identical, but different from those of other lambs in the flock.
Second, the change in the odour profiles of lambs was studied over a seven-day period. It
was found that the odour profiles of lambs are not fixed, and for as long as a ewe makes
use of olfactory recognition as the main mode of identification of her lamb she has to
continue learning the odour of her lamb. Third, the amniotic fluid was investigated as a
possible source of maternal labels, i.e. as chemical codes consisting of mixtures of compounds in specific quantitative ratios that are imprinted on lambs by their mothers at
birth. It was found that the amniotic fluids of first- and second-born lambs are
qualitatively and quantitatively different. It is possible that the duration of the lambing
birth process could contribute to this change in amniotic fluid composition. Fourth, the
role of residual proteins in the dissemination of the semiochemicals involved in ewe–
lamb communication was investigated and six proteins were identified as amniotic fluid
and wool-associated proteins.
Bioassays carried out during the lambing season of 2009 confirmed the role of the
odour of the lamb in ewe-lamb recognition, but bioassays carried out with synthetic
pheromone formulations gave inconclusive results. / AFRIKAANSE OPSOMMING:
Skaapboerdery lewer aansienlike bydrae tot die ekonomie van Suid Afrika,
maar lamsterftes is een van die kwellende probleme waarmee kleinveeboere te kampe het.
Die eksklusiewe band wat binne die eerste paar uur na 'n lam se geboorte tussen die ooi en
haar lam ontwikkel, is die hooffaktor waarvan lammers se oorlewing afhang. Hierdie
sterk binding tussen lam en ooi is 'n bekende verskynsel in alle skaap-rasse en dit is
bekend dat 'n feromoon wat deur die lam vrygestel word, dit vir die ooi moontlik maak
om haar lam aan sy unieke reuk uit te ken. Lamsterftes sou aansienlik verminder kon
word as hierdie feromoon geïdentifiseer en gebruik kan word om ooie te verhoed om
hulle eie lammers te verwerp en om die aanvaarding van vreemde lammers deur ooie
moontlik te maak.
Die doel van hierdie studie was die chemiese karakterisering van die vlugtige
organiese verbindings aanwesig in die amniotiese vloeistof en wol van Döhne Merino
lammers ten einde 'n beter begrip van die semiochemiese kommunikasie tussen ooie en
lammers te verkry. In die amniotiese vloeistof is 70 vlugtige organiese verbindings
geïdentifiseer. Dieselfde verbindings asook 'n verdere 63 verbindings is in lammerwol
geïdentifiseer. Die meerderheid van hierdie verbindings is reeds voorheen in verskeie
soogdierafskeidings gevind.
Die studie het verskeie interessante aspekte van hierdie semiochemiese
kommunikasie aan die lig gebring. Eerstens is daar gevind dat die samestelling van die
vlugtige organiese materiaal in die wol van tweelinglammers, oftewel hul reukprofiele,
feitlik identies is. Verder verskil die reukprofiele van 'n tweeling van dié van ander
tweelinge en enkelinge in die trop. Tweedens is gevind dat die reukprofiel van 'n lam nie
by geboorte vasgelê word en so behoue bly nie, maar dat dit geleidelik verander oor ten
minste die periode van sewe dae waaroor hierdie verskynsel bestudeer is. Dit noodsaak
die ooi om haar geheue met betrekking tot die lam se reuk voortdurend te verfris
gedurende die tydperk wat sy hoofsaaklik van haar reuksin gebruik maak om haar lam te
herken. Derdens is die amniotiese vloeistof ondersoek as moontlike bron van ‘n
sogenaamde moedermerk, waardeur chemiese mengsel van verbindings wat in ‘n
spesifieke kwantitatiewe samestelling by geboorte deur die ooi op haar lam agter gelaat word. Ten opsigte van kwalitatiewe en kwantitatiewe samestelling, verskil die vlugtige
organiese fraksie van die amniotiese vloeistof van die tweelinglam wat eerste gebore
word van die amniotiese vloeistof van die lam wat tweede gebore word. Dit is
onwaarskynlik dat amniotiese vloeistowwe wat ten opsigte van hul vlugtige organiese
fraksies van mekaar verskil, nagenoeg identiese moedermerke op tweeling lammers sou
kon laat. Vierdens is vasgestel dat spore van ses proteïene uit die amniotiese vloeistof op
die wol van lammers agtergelaat word. Daar kon ongelukkig nie vasgestel word of
hierdie proteïene 'n rol in die vrystelling van semiochemiese inligting speel nie.
Gedragstoetse wat tydens die lamseisoen van 2009 uitgevoer is, het bevestig dat
die lam se reukprofiel deurslaggewende rol in ooi-lam herkenning speel, maar
gedragstoetse wat met sintetiese feromoonmengsels uitgevoer is, het onbesliste resultate
opgelewer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/3980 |
| Date | 03 1900 |
| Creators | Viviers, Marlize Zaretha |
| Contributors | Burger, B. V., Le Roux, M., University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
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