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Effect of Feeding Mixed Forage Diets on Milk Production
Fitzgerald, J.J. Murphy, J.J.
Fitzgerald, J.J.
Murphy, J.J.
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1999-02-01
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Fitzgerald, J.J., Murphy, J.J., Effect of Feeding Mixed Forage Diets on Milk Production
Abstract
For dairy farmers involved in winter milk production a high intake of
forage is required by autumn calved dairy cows to produce a high milk
yield with a moderate level of concentrate supplementation. Since
intake of grass silage is often limiting, alternative forages or feeds
may be needed to maximise forage intake. In areas not suitable for
growing maize alternative forages need to be considered. These
could include limited amounts of very high quality grass silage (DMD
750-800 g /kg), grazed autumn pasture or bulky by-product feeds,
e.g. superpressed sugar beet pulp.
An experiment was conducted involving 5 treatments in which a standard good
quality grass silage (S) was partially replaced with either very high quality grass
silage, which was either unwilted (U) or wilted (W), ensiled pressed sugar beet
pulp (P) or with autumn pasture (G). These additional feeds were fed at a level
of 5 kg DM/day to autumn calved cows in early lactation over a period of 8
weeks from late October to late December. The pressed pulp diet (P) included
0.5 kg DM soyabean meal to increase its protein level. The autumn grass was
cut daily and fed indoors. The additional feeds were fed on top of the standard
silage in individual feeding boxes and the standard silage was fed ad libitum to
cows on all treatments. The cows were fed concentrates at 6 kg/day in two
feeds on all treatments.
The digestibility of the standard grass silage (754 g DMD/kg) was higher than
planned and was only slightly less than that of the high quality supplementary
silages (783 g DMD/kg). Feeding the U and W silages did not increase total
forage intake but did increase milk yield by 1.7 - 1.9 kg/day compared with
silage S alone.
Milk fat and protein concentration tended to be reduced on the diets containing
U and W silages, consequently yield of fat and protein were not significantly
increased compared with silage S. Forage intake was increased by 8% (0.8 kg
DM/day) when silage S was supplemented with autumn grass and milk yield
was increased by 1.5 kg/day without affecting milk composition. Intake of
silage was reduced by 37% by feeding grass. Feeding the pressed pulp
supplement (P) increased intake of forage (+1.1 kg DM/day), increased milk
yield by 2.7 kg/day and also improved milk protein concentration and yield
(+121 g/day). Cows gained in liveweight to a similar extent on all diets. It was concluded that feeding pressed pulp with a good quality grass silage had
the greatest effect on forage intake and milk production whereas feeding high
quality grass silages or autumn grass had a smaller effect. Larger increases in
intake and milk production would be expected from these feeds if the standard
grass silage was of lower digestibility (~700 g DMD/kg), similar to average
quality first cut silage.