ENGLISH ABSTRACT: Kikuyu over-sown with ryegrass forms the basis of pasture based systems in the Southern Cape. During
early spring, energy is the first limiting nutrient in kikuyu/ryegrass pasture, supplementation is thus
essential. Supplementation consists mainly of high starch concentrates (high maize inclusion), which is
expensive and could negatively affect rumen parameters. The objective of this study was to determine if
milk production could be improved or maintained, and if the rumen environment would be improved, by
replacing high starch concentrates with low starch (high by-product) concentrates for dairy cows on
kikuyu/ryegrass pasture.
Forty-five multiparous, high producing, lactating Jersey cows [body weight, 340 ± 34.7 kg; milk yield (MY),
19.6 ± 2.23kg/d; days in milk (DIM), 153 ± 33.5; lactation number, 3.6 ± 1.85; (mean ± SD)] were used in
the production study. A randomised block design was used. The forty-five cows were allocated to fifteen
groups of three each (blocking) on the basis of MY, DIM, and lactation number. Cows from each group
were randomly allocated to one of three treatment groups (high starch, medium starch and low starch
concentrate supplementation). Cows were fed 6kg (3kg during each milking) concentrate per day and
were allocated fresh pasture ad lib after each milking. There were no significant differences (P > 0.05)
found in milk yield and fat corrected milk yield between treatment groups. Milk fat percentage was
significantly higher (P < 0.05) in the low starch treatment than in the high starch treatment. Milk fat yield
was significantly higher (P < 0.05) in both the low starch and the medium starch treatment when
compared to the high starch treatment. Milk protein and lactose percentages, as well as milk urea
nitrogen and somatic cell count, did not differ significantly (P > 0.05) between treatments. Live weight
change, as well as body condition score change, was unaffected (P > 0.05) by treatments indicating body
reserves were not used to maintain milk production in the low starch treatment. A rumen metabolism study was also done with ten lactating, cannulated Jersey cows [body weight, 332 ±
56.3 kg; MY, 17.3 ± 1.73kg/d (mean ± SD)] were used. The cows were divided into two groups of five
each, on the basis of lactation number, DIM, and MY. The five cows from each group were randomly
allocated to one of two treatment groups (high starch and low starch concentrate supplementation) and
used in a cross-over design. Cows were fed 6kg concentrate per day and were allocated fresh pasture ad
lib after each milking. The volatile fatty acid (VFA) concentration was significantly higher (P < 0.05) in the
high starch treatment when compared to the low starch treatment. The individual VFA’s, acetic-,
propionic- and butyric acid concentrations were also significantly higher (P < 0.05) in the high starch
treatments when compared to the low starch treatment. The acetic to propionic acid ratio was unaffected
(P > 0.05) by treatment. Rumen ammonia-nitrogen concentration was significantly higher (P < 0.05) in the
high starch treatment. Rumen pH was unaffected (P > 0.05) by supplementation type. The in sacco dry
matter and neutral detergent fibre digestibilities of the kikuyu/ryegrass pasture were unaffected (P > 0.05)
by treatment type.
Results indicated that milk production could be maintained with low starch concentrates which also
improved milk composition. Results further suggested that the rumen environment was relatively
unaffected by low starch concentrate supplementation.
AFRIKAANSE OPSOMMING: Kikoejoe, oorgesaai met raaigras, vorm die basis van weidingstelsels in the Suid-Kaap. Tydens die
lentemaande is energie die eerste beperkende voedingstof op kikoejoe/raaigras weidings, wat
kragvoeraanvulling noodsaaklik maak. Aanvulling bestaan grootliks uit hoëstysel-kragvoer (hoë mielieinhoud)
wat nie net duur is nie, maar dit kan ook die rumenomgewing benadeel. Die doel van die studie
was om vas te stel of melkproduksievlakke onderhou kan word en of rumenomgewing verbeter kan word
deur die vervanging van hoëstysel-kragvoer met laestysel-kragvoer (hoë neweprodukinhoud) vir
melkkoeie op kikoejoe/raaigras weidingstelsels.
Vyf-en-veertig meervoudige pariteit-, hoë produserende, lakterende Jerseykoeie [liggaamsmassa, 340 ±
34.7 kg; melkproduksie, 19.6 ± 2.23kg/d; dae in melk, 153 ± 33.5; laktasienommer, 3.6 ± 1.85; (gem ±
standaardafwyking)] is gebruik vir die produksiestudie van die proef. Daar is gebruik gemaak van ‘n
ewekansige blokontwerp. Die vyf-en-veertig koeie is opgedeel in vyftien groepe van drie elk, gebaseer op
melkproduksie, dae in melk en laktasienommer. Koeie in elke groep is ewekansig aan een van drie
behandelings (hoëstysel-, mediumstysel- of laestysel-kragvoeraanvulling) geallokeer. Koeie is daagliks
6kg (3kg tydens twee milkings) kragvoer gevoer en vars weiding was ad lib beskikbaar na elke melking.
Daar was geen beduidende verskil (P > 0.05) in melkopbrengs of vet-gekorrigeerde melkopbrengs tussen
die drie behandelings nie. Bottervetpersentasie was beduidend hoër (P < 0.05) in die
laestyselbehandeling in vergelyking met die hoëstyselbehandeling. Bottervetopbrengs was beduidend
hoër (P < 0.05) in beide die laestysel- en mediumstyselbehandelings in vergelyking met die
hoëstyselbehandeling. Melkproteïen- en melklaktosepersentasies, asook melkureumstikstof en somatise
seltelling, was onveranderd (P > 0.05) tussen behandelinge. Liggaamsmassa en liggaamskondisietelling
het geen verskille (P > 0.05) getoon tussen behandelings nie, wat daarop dui dat liggaamsreserwes nie
gebruik is om melkproduksie in die laestyselbehandeling te onderhou nie. ‘n Rumenmetabolismestudie is ook uitgevoer met tien lakterende, gekannuleerde Jerseykoeie
[liggaamsmassa, 332 ± 56.3 kg; melkproduksie, 17.3 ± 1.73kg/d (gem ± standard afwyking)]. Die koeie is
in twee groepe van vyf elk verdeel, gebasseer op laktasienommer, dae in melk en melkproduksie. Die vyf
koeie van elke groep is in ‘n omslagontwerp gebruik en is ewekansig aan een van twee behandelings
(hoëstysel- of laestysel-kragvoeraanvulling) geallokeer. Koeie het daagliks 6kg kragvoer ontvang en vars
weiding was ad lib beskikbaar na elke melking. Die vlugtige vetsuurkonsentrasie was beduidend hoër (P
< 0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Die individuele vlugtige vetsure
naamlik asynsuur, propionsuur en bottersuur, was ook beduidend hoër (P < 0.05) in die
hoëstyselbehandeling as in die laestyselbehandeling. Die asynsuur- tot propionsuurverhoudings het geen
verskille (P > 0.05) tussen behandelings getoon nie. Rumen-ammoniakstikstof was beduidend hoër (P <
0.05) in die hoëstyselbehandeling as in die laestyselbehandeling. Rumen-pH het geen verskille (P > 0.05)
getoon tussen behandelings nie. Die in sacco droëmateriaal- en neutraalbestande veselverteerbaarhede
van kikoejoe/raaigras weiding het geen verskille (P > 0.05) tussen behandelings getoon nie.
Die resultate het aangedui dat melkproduksie onderhou kan word en dat melksamestelling verbeter kan
word met laestysel-kragvoeraanvulling. Resultate het ook daarop gedui dat die rumenomgewing nie
noodwendig verbeter word deur die aanvulling van laestysel-kragvoer vir koeie op kikoejoe/raaigras
weidings nie.
