25 December 1998

High DM feeds needed to support high yields

NUTRITION is catching up with the rapid increase in cow genetic merit, but higher dry matter intakes are essential to support these higher yields.

That was the message from Liam Sinclair of Harper Adams at the seminar. Achieving higher intakes will help control condition score loss, he said. "Cows are losing a considerable amount of weight even 20 weeks into lactation. That is where our challenge lies."

He cited a CEDAR, Reading University, study which revealed liveweight losses of 2.3kg a day five weeks into lactation and 1.7kg a day after 20 weeks milking, for a cow yielding 52 litres and 44 litres, respectively.

To maximise intakes cows must be offered feed ad lib, which means accepting 5% refusals each day. They also have to be offered concentrates frequently to avoid rumen disturbances. "You cannot feed 13kg of concentrates in two feeds. Some concentrate must be fed outside, but the system need not be complicated," said Mr Sinclair.

Total mixed rations allow different ingredients to be used, but may not increase milk yields compared with out-of-parlour feeders offering concentrates five times a day. Out-of-parlour feeders also encouraged higher silage intakes, according to studies in Northern Ireland.

Silage quality can also affect cow performance, especially when lower levels of concentrate are fed. But it is the quality of silage-making that affects cow intakes and performance most, and this cannot be seen in a silage analysis.

A study, comparing good silage-making practices with poor, showed that using a full-rate additive, quickly filling the pit, compacting grass well and sheeting overnight during silage-making was worthwhile. It resulted in 1.5kg a cow higher silage intakes and 2 litres more milk a day, despite no difference in silage analysis results.

Mixed forage diets also improve cow intakes. "Although maize is potentially the best feed, it may not be the best option when yields are only 7-8t/ha of dry matter," said Dr Sinclair.

When at grass, high yielders could not eat enough grass dry matter to support yields, but they could be fed concentrate economically. Cows could only support yields of 27-30 litres from grass alone. Although response rates to concentrates were poor for lower yielders, they improved for higher yielders giving above 35 litres.


&#8226 Accept some waste.

&#8226 Silage-making practice important.

&#8226 Offer mixed forage diets.