Thesis (MScAgric)--Stellenbosch University, 1999. / ENGLISH ABSTRACT: The rate of hydrolysis of urea in the rumen of animals is a major limitation when
considering the substitution of natural protein with urea in the formulation of rations.
The aim of this study was to evaluate polymer coated urea prills with variable coating
thickness and evaluate its potential as a slow-release NPN compound. A new slowrelease
urea compound, made by coating prilled feedgrade urea with a co-polymer
of urea-formaldehyde resin and a castor-coconut alkyd was initially evaluated for
urea-nitrogen concentration in distilled water in order to evaluate its potential as a
slow-release urea product for ruminants. Amino/alkyd or polyester blends are
among the cheapest of the modern synthetic systems and are considered because it
is non-toxic, low-cost, biodegradable and easy to manufacture. A 2 x 2 x 2 x 2
factorial design was used and 16 individual products were made and evaluated. The
Wurster method was used to encapsulate urea prills. The slopes of the urea release
curves represented the release rate of the encapsulated products and were
compared to identify the process variables, which had an effect on release rate. Two
of the coating variables, coating weight and alkyd: resin ratio, had a major effect (P =
0.0001) on the release rate of urea. The crushing strength of encapsulated products
was significantly (P = 0.0001) higher than that of untreated urea. Results motivated
the evaluation of the products in the rumen of sheep in terms of rumen ammonia and
blood urea N concentrations. Four slow-release products were made after
interpreting results from the first study, and differed on account of the coating weight and the composition of the co-polymer. Fifteen fistulated wethers were randomly
allotted into 5 groups and intraruminally received an equivalent of 15g urea. Rumen
ammonia and blood ammonia were taken at 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48
h after administration of the various treatments. Slow release urea (SRU) resulted in
significantly lower rumen ammonia peaks (P = 0.0001) than untreated urea, while the
peaks were also significantly delayed. Untreated urea resulted in the maximum
concentration at two hours after administration of the urea (P = 0.0685) while the
SRU's reached a maximum at six hours after administration in the rumen. No
significant differences between the four different SRU types were found. Responses
in blood urea-N was similar to that observed for rumen ammonia nitrogen. The
encapsulation was effective in decreasing the rate of ammonia release from the urea
for up to six hours after administration. In a third trial four Dehne Merino wethers
were used in a 2 x 2 Latin square design. They received a SRU product equivalent to
0.4 g urea per kg body weight orally. Rumen liquor and blood samples were taken at
0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h after intake. Difficulty was initially
experienced with ingestion and palatability of the SRU products due to the strong
formaldehyde and butanone odour present in the coating. The maximum rumen
ammonia (NH3) concentration for the SRU were lower than that of untreated urea
(17.5 mg N/dl vs. 66.9 mg N/dl). The time to reach blood urea levels also differed
considerably (6 h vs. 24 h for blood urea nitrogen) between treatments.
The encapsulation of urea prills shows potential solutions to reduce the solubility of
urea and also reduce the hygroscopic nature of urea and improve the palatability and
storage characteristics thereof.
Keywords: Slow-release urea, encapsulate, copolymer, urea formaldehyde rumen
ammonia, blood urea nitrogen, solubility, palatability, storage characteristics. / AFRIKAANSE OPSOMMING: Die vinnige tempo waarteen ureum in die rumen na ammoniak omgesit word, is die
grootste beperking in die optimale benutting van ureum, as vervanging van
natuurlike protein in herkouerrantsoene. Die doel van hierdie studie was om 'n
stadig vrystellende ureumproduk te ontwikkel wat die rumenammoniakvlak
gedurende 'n aansienlike periode van die dag bokant 'n sekere vlak kan hou. 'n
Nuwe stadig vrystellende ureumproduk, vervaardig deur ureumkorrels met 'n
kopolimeer van ureum-formaldehiedhars en 'n kastor-en klapperalkied te bedek, is
geevalueer om die potentiaal as stadig vrystellende nie-protein stikstof (NPN)-produk
vir herkouers te ondersoek. Die veiligheid, biodegradeerbaarheid, lae koste en
maklike vervaardiging van amino/alkied-kopolimere maak dit een van die
goedkoopste sintetiese sisteme om vir stadig vrystellende sisteme te oorweeg. 'n 2
x 2 x 2 x 2 Faktoriale antwerp is gebruik om 16 individuele produkte te vervaardig.
Die Wurster-metode is gebruik om individuele korrels te enkapsuleer met die
polimeer en die potentiaal van die produkte is aanvanklik geevalueer deur die
ureumstikstofvrystelling in gedistilleerde water te meet. Die hellings van die
vrystellingsgrafieke is vergelyk om die veranderlikes te bepaal wat die grootste
invloed op die vrystellingstempo van ureum uit die ge·inkapsuleerde produkte het.
Resultate dui dat twee verandelikes 'n betekenisvolle effek het op die vrystellingstempo, nl. dikte van die omhulsel, en die samestelling van die kopolimeer
(P = 0.0001 en P = 0.0135, onderskeidelik) het. Die samedrukbaarheid van die ge
·lnkapsuleerde produkte was ook betekenisvol hoer (P = 0.0001) as die van
onbehandelde ureumkorrels, wat lei tot verbeterde bergings- en
hanteringseienskappe. lnterpetering van resultate lei tot die vorming van vier stadig
vrystellende produkte. Vyf groepe van 3 volwasse rumengefistuleerde
Dohnemerinohamels is in 'n proef gebruik om die potentiaal van die produkte verder
te ondersoek. 'n Ekwivalent van 15 g ureum is direk in die rumen van elke dier
geplaas en ammoniak-en bloed monsters is 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 & 48
ure na dosering geneem. Die stadig vrystellende ureumprodukte het 'n betekenisvol
laer maksimum waardes vir beide ammoniak-en bloedstikstofureum getoon (P =
0.0001 ). Onbehandelde ureum het 'n maksimum rumenammoniakstikstof
konsentrasie reeds twee ure na toediening bereik in vergelyking met ses ure vir die
stadig vrysellende produkte. Geen betekenisvolle verskille in hierdie parameters is
tussen die ge·lnkapsuleerde produkte gevind nie, terwyl geen interaksie is tussen
hoofeffekte voorgekom het nie. In 'n derde proef is vier Dohnemerinohamels gebruik
om die vrystellingstempos, in terme van rumenammoniak-en bloedureumstikstof te
bepaal waar die stadig vrystellende produk en onbehandelde ureum direk aan die
diere gevoer is . 'n Ekwivalent van 0.4 g ureum/kg liggaamsmassa is gevoer.
Aanvanklik is inname- en smaakliksheidprobleme ondervind, moontlik as gevolg van
die sterk butanoon-en formaldehiedreuk van die omhulsel. Die
rumenammoniakstikstof het 'n laer maksimum (17.5 vs. 66.9 mg N/1 00 ml) as die
van onbehandelde ureum gehad terwyl die tyd wanneer maksimum konsentrasie
bereik word ook aansienlik later was. Die polimeer inkapsulering van ureumkorrels
toon potensiaal as 'n stadig vrystellende ureumproduk deurdat dit die oplosbaarheid
van ureum in die rumen verlaag. Bykomende voordele is dat die omhulsel die
higroskopisiteit verlaag en die samedrukbaarheid verhoog, beide eienskappe wat die
hantering-en bergingseienskappe bevorder.
Sleutelwoorde: Stadig vrystellende ureum, enkapsulering, kopolimeer, ureumformaldehied,
rumenammoniak, bloed ureum stikstof, oplosbaarheid, smaaklikheid,
bergingseienskappe.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51199 |
| Date | January 1999 |
| Creators | Upton, Erlanda |
| Contributors | Coetzee, J., Cruywagen, C. W., Sanderson, R. D., 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 | Unknown |
| Type | Thesis |
| Format | 81 p. : ill. |
| Rights | Stellenbosch University |
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