Cut DM and reduce
spring milk output
RESTRICTING grass dry matter allowance to 16 or 17kg a cow reduced spring milk production by up to 12% in both spring and autumn calvers, compared with cows offered 20kg of grass dry matter.
So says Teagasc, researcher Gearoid Stakelum at Irelands Moorepark research centre, Fermoy, Co Cork. But offering cows over 20kg DM of grass a day will not increase yields further, he adds.
That is the early finding of his study offering grazed grass dry matter at three different levels. Each level of dry matter allowance is offered to a group of 14 spring and 14 autumn calvers.
But increased levels of grass DM allowance showed higher milk protein contents throughout the six groups, he adds.
"In spring and summer the effect of herbage allowance is huge on the spring calving cows," says Dr Stakelum. "There was no benefit from from increasing DM allowance to cows in later lactation, so these animals had passed their peak appetite.
"When you know how much grass to offer you can organise grazing management to ensure a specific amount of feed is kept on the farm and then ration it out to the cows."
It is then important to work out the implications of rotational grazing speeds so that when grass runs short it is easier to determine when to begin offering supplements. Surpluses can also be identified and then cut for silage. But Dr Stakelum advises against offering autumn-calved cows unsupplemented grazed grass in early lactation. In his study autumn calvers fed grazed grass without concentrate or silage grazed grass down too hard compared with those fed 3kg or 6kg of concentrates. Their milk yields were 22.5, 25 and 27 litres, respectively, in November.
The cows should have been offered some concentrate from the start of the study to reduce the risk of weight loss, he adds. *