Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Statistical analysis was conducted on data from two Elsenburg herds, containing 105 Jersey
and 232 Holstein cows. The data was examined for external factors which may affect milk
yield and milk composition. The data consisted of 337 first lactation records, taken over a 20
year time period. Breed of cow had an effect on milk yield, butterfat and protein production,
as did the year in which the cows were born and the age of the heifer at first calving. There
was a significant interaction between the breed and year of birth. There are other external
factors, which are difficult to quantify, which may have an effect on production. In the
following trials, eight ruminally cannulated dairy cows (four Jerseys and four Holsteins) were
used to determine the effect of breed on forage digestibility in the rumen. All cows received a
high concentrate mixed ration, with supplementary wheat straw. An in situ rumen
degradability trial was conducted with three different forages, viz. lucerne, wheat straw and
NaOH-treated wheat straw. The bags were incubated in the rumen for time intervals of 2,4,
8, 12, 16,20,24, 36,48, 72 and 96 hours and samples were analysed for dry matter (DM) and
neutral-detergent fibre (NDF). Higher rumen degradability values (P<0.01) ofDM and NDF
were observed in Jerseys for all three forages. Differences were more apparent for wheat
straw and treated wheat straw than for lucerne. The rate of passage of digesta from the rumen
was measured in both breeds by a chromium mordanted wheat straw marker. The Holsteins
manifested a higher rate of passage (P<0.05) than the Jerseys, while daily feed intakes were also higher (P<O.Ol) for the Holsteins than for the Jerseys. Daily feed intake, expressed as
percentage of body weight was, however, slightly higher for the Jerseys than for the
Holsteins. The pH value of the rumen fluid was measured at 0, 4, 8, 10 and 12 hours postfeeding.
The only significant difference (P<O.OI)in pH between the breeds was at 4 hours
post-feeding, when the ruminal pH dropped more rapidly in the Holsteins than in the Jerseys.
The pH in the Holsteins dropped below 6.2, which may have inhibited fibrolytic microbe
activity in the rumen, resulting in a lower effective degradability of forages. Total volatile
fatty acids were higher in Holsteins from four to 10 hours after feeding, but no differences
were observed in acetic acid:propionic acid ratios. It was concluded that Jerseys appear to
utilize forages more efficiently than Holsteins and that the differences are more apparent in
low quality forages than in high quality forages. / AFRIKAANSE OPSOMMING: Statistiese analises is op data van twee kuddes te Elsenburg uitgevoer, bestaande uit 105
Jersey- en 232 Holsteinkoeie. Die data is ondersoek vir eksterne faktore wat melkproduksie
en melksamestelling kan beinvloed. Die data het uit 337 eerste-laktasierekords bestaan, wat
oor 'n periode van 20 jaar ingesamel is. Ras van die koei, sowel as die jaar van geboorte en
ouderdom met eerste kalwing het 'n invloed op melkproduksie, bottervet- en proteienopbrengs
gehad. 'n Betekenisvolle interaksie is tussen ras en jaar van geboorte waargeneem.
Ander moeilik kwantifiseerbare faktore mag ook 'n invloed op melkproduksie he. In
daaropvolgende proewe is agt rumen-gekannuleerde melkkoeie (vier Jerseys en vier
Holsteins) gebruik om die invloed van ras op ruvoerverteerbaarheid in die rumen te bepaal.
Al die koeie het 'n hoe-kragvoerdieet ontvang, aangevul met koringstrooi. 'n In situ
rumendegradeerbaarheidstudie is met drie verskillende ruvoere, naamlik lusernhooi,
koringstrooi en NaOH-behandelde koringstrooi uitgevoer. Die ruvoere is vir tye van 2, 4, 8,
12, 16, 20, 24, 36, 48, 72 en 96 ure in die rumen geinkubeer en monsters is ontleed vir
droemateriaal (DM) en neutraal-bestande vesel (NDF). Hoer rumen-degradeerbaarheidswaardes
(P<O.Ol) van DM en NDF is in Jerseys waargeneem as in Holsteins vir al drie
ruvoere. Verskille was meer opvallend vir koringstrooi en NaOH-behandelde koringstrooi as
vir lusem. Uitvloeitempo van digesta uit die rumen is in beide rasse met behulp van
chroomgemerkte koringstrooi bepaal. Hoer uitvloeitempo's is in die Holsteins waargeneem
as in die Jerseys, terwyl daaglikse voerinnames ook hoer was (P<O.05) by die Holsteins as by die Jerseys. Daaglikse voerinname, uitgedruk as persentasie van liggaamsmassa, was egter
effens hoer (P<O.OI)by die Jerseys as by die Holsteins. Die pH van die rumenvloeistof is op
0, 4, 8, 10 en 12 ure na voeding gemeet. Die enigste betekenisvolle verskil (P<O.OI)in pH
tussen die rasse het op 4 ure na voeding voorgekom toe die pH van die rumeninhoud vinniger
in die Holsteins as in die Jerseys gedaal het. Die pH in die Holsteins het onder 6.2 gedaal,
wat moontlik fibrolitiese mikrobe-aktiwiteit in die rumen kon inhibeer, met 'n gevolglike
daling in effektiewe degradeerbaarheid van die ruvoere. Vanaf 10 ure na voeding was die
totale vlugtige vetsuurkonsentrasies hoer in die Holsteins, maar geen verskille in
asynsuur:propionsuurverhoudings is waargeneem nie. Die gevolgtrekking is gemaak dat
Jerseys skynbaar meer doeltreffend is om ruvoere te benut as Holsteins en dat die verskil
tussen rasse meer opvallend is vir lae kwaliteit ruvoere as vir hoe kwaliteit ruvoere.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51641 |
| Date | 11 1900 |
| Creators | Retief, Nicky |
| Contributors | Schoeman, S. J., Cruywagen, C. W., 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 | xii, 55 p. : ill. |
| Rights | Stellenbosch University |
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