SPRING GRASS is often perceived as one of the cheapest and most nutritious feeds available, but its continual change in quality throughout the season can cause chaos in dairy cow performance – affecting milk yields and overall cow health.

Milk yields often jump the first week at grass, but, according to animal nutritionists, poor rumen utilisation of rich spring grass can result in cows losing weight which ultimately affects cow health and fertility.

“You never get the same feed conversion efficiency feeding cows at grass because grass quality and intakes are so variable,” Mark Voss, a dairy cow nutritionist with Keenan, told farmers at Largs Farm, Twynholm, last week.

“Milking cows can’t physically consume the amount they require at grass – the maximum they will eat is 18kg per day and to do that they have to actively graze for 10-12hours a day.

Intakes are so variable – the average figure is nearer 14kg per day – and if you feed too many concentrates to make up the shortfall, you can end up with cows going down with rumen acidosis.

Mr Voss added that even on the best quality grass, cows would be lucky to eat 2.8% of their own bodyweight in grass feed, whereas housed cows on a TMR consume 4% of their bodyweight.

Instead, he urged farmers to concentrate more on a consistent diet throughout the entire milking period, enabling the rumen microbes to operate at their best. This, he said, can be achieved by controlled loading of feed ingredients in the correct order and correct processing of long forages in the TMR at all times.

He pointed to the new Keenan PACE (Performance Acceleration and Control Enhancement) system which is designed to optimise ration consistency and has enabled cows to produce better yields with higher solids and increased margins.

It appears to be working at Largs Farm, too, where James and Elizabeth Wilson, and son Crawford, have been using the system since October, 2008, following a breakdown of IBR in their herd.

Although comparisons are difficult, the family feels their new consistent, TMR feed system is easier to manage and the cows, as a result, are healthier on it, averaging 9600kg on a twice daily milking regime without in parlour feeding.

According to Greg Dall, of Yara Fertilisers, nitrogen is still the key nutrient, but yields are often higher where phospate and potash levels are good. Sulphur is also gaining recognition as the fourth main nutrient, and one that Mr Dall pointed out is ‘very under applied.’