Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Veal production is a specialised form of calf rearing in which calves were traditionally
raised on all-liquid diets. The early weaning of calves onto concentrated diets provides
an economically viable alternative rearing method with comparable calf performance.
The emphasis in meat production has shifted to the production of lean meat, therefore
the deposition of protein instead of fat has become a priority. The optimum level of
dietary crude protein for growing calves is well established. Very little, however, is
known about the influence of protein degradability in the diet of young ruminants.
Recommendations by the NRC are derived from data obtained using lactating dairy
cows. The aim was to obtain data on which recommendations for the level of
degradable protein in starter and finisher diets for calves could be based.
Two experiments were conducted to examine the effect of different levels of dietary
crude protein degradability in starter and finisher calf diets on veal calf performance. In
both experiments Holstein bull calves were 3 - 10 days of age at the onset, weaned at 4
weeks of age and slaughtered at 20 weeks of age for veal. In Experiment 1 calves were
randomly assigned to one of three treatments: low (LO), medium (MD) and high (HO)
rumen degradable protein. Calves received a starter diet up to 11 weeks of age and
finisher diets from week 12 - 20. In Experiment 2 calves received a starter diet either
high or low in rumen degradable protein up to 10 weeks of age. In the finishing period
(week 11 - 20) both the low and high groups were again divided into a low and high
group, resulting effectively in 4 treatments, viz. LL, LH, HL and HH. The diets in both
experiments were formulated to be iso-nitrogenous and iso-caloric, differing only in
rumen undegradable protein content within periods and. respective experiments. Body weight gain, feed intake and feed conversion efficiency data for the preweaning,
starter, finishing and total experimental period was compared between treatments.
There were no significant differences for feed intake, body weight gain or feed efficiency
in the starter period of both experiments between treatments. In the finishing period of
Experiment 1 the average daily gain for the LO treatment was significantly higher than
for the HO treatment, with the MD treatment having an intermediate value. The feed
conversion ratio (FCR) for the LO treatment was also significantly better than for the
other two treatments. In Experiment 2 the FCR tended (P = 0.0984) to differ between
treatments in the finishing period. Calves from the LL and HL treatments had a more
favourable FCR than calves from the LH treatment. The HH treatment had an
intermediate FCR. According to these results crude protein degradability appears to
have an effect on the FCR in the finishing period.
The lack of response to higher levels of undegradable dietary protein in calves younger
than 10 weeks may be due to underdeveloped rumen functions and it seems possible
for high degradable protein to escape degradation to a higher extent than at a later age.
In a third experiment, Holstein bull calves and Holstein cows were used to determine
and compare the dry matter and crude protein degradability of the four calf diets used in
Experiment 2. Rumen VFA concentrations, pH level and NH3-N concentrations were
measured for the cannulated Holstein calves to evaluate the level of rumen metabolic
maturity of growing calves. Five Holstein bull calves were ruminally cannulated at 6
weeks of age. Dry matter and crude protein degradability were determined once weekly
from week 8 - 20 by means of 24 h in sacco incubations. Three ruminally cannulated
Holstein cows were used to determine the comparable values for mature ruminants.
Dry matter and crude protein degradability differed significantly between the low and
high degradable diets for both calves and cows. Dry matter and crude protein
degradability in calves increased up to 11 and 12 weeks of age respectively, and then
appeared to remain constant to week 20. Dry matter and crude protein degradability
values of the starter diets were lower for the calves than for the cows, but values were
similar for the finisher diets. Rumen VFA concentrations, pH level and NH3-N
concentration showed some fluctuation between weeks, but were similar to literature
values for mature animals. / AFRIKAANSE OPSOMMING: Titel: Die invloed van verskillende vlakke van proteïendegradeerbaarheid
in aanvangs- en afrondingsdiëte op kalfprestasie in
'n kalfsvleisproduksiestelsel.
Kalfsvleisproduksie is 'n gespesialiseerde grootmaakstelsel wat tradisioneel alleenlik op
vloeistofdiëte gebaseer was. 'n Stelsel waar kalwers vroeg gespeen word en 'n
volledige aanvangs- en afrondingsrantsoen ontvang, bied 'n alternatiewe metode wat
ekonomies lewensvatbaar is en vergelykbare kalfprestasie tot gevolg het. Die klem in
vleisproduksie het verskuif na die produksie van maervleis. Die neerlegging van
proteïen in plaas van vet het dus 'n prioriteit geword. Die optimale vlak van
dieetproteïen vir groeiende kalwers is deeglik nagevors. Baie min is egter bekend oor
die invloed van proteïendegradeerbaarheid in die dieet van jong herkouende diere.
Aanbevelings deur die NRC is afkomstig van data verkry van studies met
melkproduserende koeie. Die doel was om data te bekom waarop aanbevelings vir die
vlak van degradeerbare proteïen in aanvangs- en afrondingsdiëte vir kalwers gegrond
kan word.
Twee eksperimente is uitgevoer om die invloed van verskillende vlakke van
proteïendegradeerbaarheid in aanvangs- en afrondingsdiëte op kalfprestasie in 'n
kalfsvleisproduksiestelsel te ondersoek. Holstein bulkalwers was 3 - 10 dae oud met die
aanvang van beide eksperimente, is gespeen op 4 weke ouderdom en op 20 weke
ouderdom vir kalfsvleis geslag. In Eksperiment 1 is kalwers ewekansig aan een van drie
behandelings toegewys: lae (LO), medium (MD) en hoë (HO) rumen degradeerbare
proteïen. Kalwers het tot op 11 weke ouderdom aanvangsdiëte ontvang, terwyl
afrondingsdiëte vanaf 12 - 20 weke ouderdom aangebied is. In Eksperiment 2 het kalwers tot op 10 weke ouderdom "n dieet wat óf hoog óf laag in rumen degradeerbare
proteïen was, ontvang. In die afrondingsperiode (week 11 - 20) is die lae en hoë
groepe elk vervolgens in "n lae en hoë groep verdeel wat effektief tot 4 behandelings
gelei het, nl. LL, LH, HL en HH. Die diëte in albei eksperimente was geformuleer om
iso-nitrogenies en iso-kalories te wees. Slegs die rumen degradeerbare proteïeninhoud
het tussen die onderskeie diëte binne "n bepaalde periode en eksperiment verskil.
Gewigstoename, voerinname en voeromsettingsdoeltreffendheid vir die voorspeense-,
aanvangs-, afrondings- en totale eksperimentele periode is tussen behandelings
vergelyk. In beide eksperimente is geen betekenisvolle verskille gedurende die
aanvangsperiode waargeneem t.o.v. voerinname, massatoename en voeromsettingsdoeltreffendheid
(VOD) nie. In die afrondingsperiode van Eksperiment 1 was die
gemiddelde daaglikse massatoename van die LO behandeling betekenisvol hoër as dié
van die HO behandeling, terwyl die MD behandeling "n intermediêre waarde gehad het.
Die VOD vir die LO behandeling was ook betekenisvol beter as vir die ander twee
behandelings. Die VOD in die afrondingsperiode van Eksperiment 2 het geneig
(P = 0.0984) om te verskil tussen behandelings en kalwers van die LL en HL
behandelings het "n meer gunstige VOD as kalwers van die LH behandeling gehad. Die
HH behandeling het "n intermediêre VOD gehad. Volgens die resultate van hierdie
eksperimente het proteïendegradeerbaarheid in kalfrantsoene waarskynlik "n invloed op
VOD in die afrondingsperiode.
Die gebrek aan respons as gevolg van hoër insluitingsvlakke van nie-degradeerbare
proteïen in die rantsoen by kalwers jonger as 10 weke kan moontlik toegeskryf word
aan onderontwikkelde rumenfunksies. Dit blyk moontlik te wees dat die hoë
degradeerbare proteïenfraksie by jonger kalwers rumendegradering in "n hoër mate as
op "n latere ouderdom vrygespring het.
In "n derde eksperiment is Holstein bulkalwers en Holstein koeie gebruik om die
droëmateriaal- en proteïendegradeerbaarheid van die vier diëte wat in Eksperiment 2
gebruik is, te bepaal en te vergelyk. Rumen WS-konsentrasies, pH-vlak en NH3-Nkonsentrasies
is vir die kalwers gemeet om die vlak van metaboliese rumen
volwassenheid van groeiende kalwers te evalueer. Vyf Holstein kalwers is op 6 weke ouderdom ruminaal gekannuleer. Droëmateriaal- en proteïen-degradeerbaarheid is een
maal per week vanaf week 8 - 20 deur middel van 24 h in sacco inkubasies bepaal.
Drie rumen-gekannuleerde Holstein koeie is gebruik om die vergelykbare waardes van
volwasse herkouers te bepaal.
Droëmateriaal- en proteïendegradeerbaarheid het betekenisvol tussen die lae en hoë
degradeerbare diëte vir beide die kalwers en koeie verskil. Droëmateriaal- en
proteïendegradeerbaarheid by die kalwers het tot op 11 en 12 weke ouderdom,
onderskeidelik, verhoog en daarna tot week 20 relatief konstant gebly. Die
droëmateriaal- en proteïendegradeerbaarheidswaardes van die aanvangsdiëte was laer
vir die kalwers as vir die koeie, maar die waardes vir die afrondingsdiëte was eenders.
Rumen WS-konsentrasies, pH-vlak en NH3-N-konsentrasies het In mate van fluktuasie
tussen weke getoon, maar was soortgelyk aan literatuurwaardes vir volwasse diere.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51967 |
| Date | 12 1900 |
| Creators | Holtshausen, Lucia |
| Contributors | Cruywagen, C. W., 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 | Unknown |
| Type | Thesis |
| Format | 82 p. : ill. |
| Rights | Stellenbosch University |
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