Performance of temperate perennial pastures in the Australian subtropics 2. Milk production
Authors: Bowdler T. M. , Casey N. D. , Moss R. J. , Lowe K. F. 
Published: September 2002

Summary. Milk production from irrigated, pure stands of
perennial ryegrass (Lolium perenne cv. Yatsyn), prairie
grass (Bromus willdenodii cv. Matua) and tall fescue
(Festuca arundinacea cv. AU Triumph) were compared with
that achieved from Italian ryegrass (L. multiflorum cv.
Concord) over 3 lactations of multiparous Holstein–Friesian cows at
Mutdapilly in south-east Queensland.
Pastures were fertilised with 50 kg nitrogen/ha . month as urea and annual
dressings of 20 kg phosphorus/ha and 50 kg potassium/ha (as
superphosphate and muriate of potash respectively). There were 4 pasture
treatments grazed at 3 cows/ha in a 1-week-on, 3-weeks-off rotation with 2
replicates and 3 cows/treatment block. Cows grazed the pastures day and
night from May to November. Over summer, cows grazed the pastures during the
night and were fed supplements (silage in the first lactation, and lucerne hay
in the second and third lactations) during the day because there was no shade
available in the irrigation areas. In autumn, the animals were removed from
the ryegrass and prairie grass pastures for 8 weeks to allow seedling
re-establishment, either by oversowing (ryegrasses) or natural reseeding
(prairie grass). Cows continued to graze the fescue pastures at night during
autumn. All cows received a ration of 4 kg/cow of a grain–minerals
mixture in the first lactation and 5 kg/cow in the second and third
lactations.
Milk production from perennial ryegrass was higher than from fescue in the
first lactation and Italian ryegrass in the second and third lactations.
Prairie grass gave similar milk production to perennial ryegrass in all 3
years. In the third year, perennial ryegrass, prairie grass and fescue gave
similar milk production. Milk quality from the 4 grasses was similar except in
the third lactation when the lactose content of milk from perennial ryegrass
pastures was lowest. There were also small and inconsistent differences in
milk component yields between the 4 grasses. Liveweight changes were small
except in the second lactation when the cows grazing fescue lost weight
relative to the other treatments. Mean liveweight at calving increased over
the 3 lactations.
It was concluded that all 3 temperate perennial grasses demonstrated useful
traits for use in subtropical dairy pastures. Perennial ryegrass produced the
most milk from the lowest amount of dry matter on offer. Prairie grass
produced similar milk yields to perennial ryegrass, was well eaten by cattle
and was self regenerating. Although fescue was slower to establish and needed
more intensive management to control maturity, it was the most persistent and
was the only grass to provide autumn grazing. In the second year this
attribute resulted in a lower requirement for supplementary feeding. Fescue
produced the highest gross margin in the second lactation and was only
marginally less than prairie grass in the third. The performance of Italian
ryegrass was as good as that of perennial ryegrass in the first lactation but
fell substantially in the second and third lactations as the level of summer
grass invasion increased.