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Dairy notes July 04

Drying off dairy cows

Early autumn calving cows will be dried off this month. Cows should be dried off for a minimum of six weeks and last year’s heifers or thinner cows should have this extended to allow them to improve. Abrupt drying off reduces the incidence of mastitis. At Greenmount Campus, a cow giving less than 20 litres is treated with an antibiotic tube and given a reduced feed supply for three days. Cows giving more than 20 litres, are fed on ad-lib straw and are milked less frequently before being treated and kept on a reduced diet.
  • The following points should be remembered when administering dry cow antibiotics:
  • Disinfect teats with methylated spirits and avoid contaminating the nozzle.
  • Always insert tube fully and massage teat upwards to aid dispersion of antibiotic.
  • Immerse the teats fully in an iodine-based dip and ensure that the cows are made to stand for 30 minutes until the teat canal closes.
  • Record drying off date.

Dry cow management

If practical, dry cows should be split into groups depending on their body condition. Thin cows (Condition Score (CS) < 2.5) should ideally receive silage aftermath plus a small level of concentrate. Fat cows (CS>3.25) should be grazed at high stocking rates to avoid an excessive increase in body condition.
Check all cows daily for signs of dry cow mastitis and keep them away from flies. Look out for animals that stand away from the rest of the group as they may be affected. At Greenmount Campus, heifers and dry cows are checked twice per day.

Water for cows

Providing enough water for cows at grass can be a problem. It is important to have big properly sited water troughs to allow groups of cows to drink.
The rules of thumb are:
  • Four litres of water are required for each litre of milk produced.
  • 50% of the daily intake occurs in the two hours after evening milking.
  • A cow will consume more than 100 litres of water each day.
Size of trough
  • 15% of the herd should be able to drink at any given time. In larger herds circular troughs will provide sufficient space.
  • Drinking rates from troughs are typically between 15 and 25 litres per minute. Where water pressure is low a 22mm feeding pipe is the minimum required and the ballcock should be properly sized.
  • A large trough capacity can compensate partly for poor flow rates. This dictates a trough size of 400 - 450 litres capable of filling at a rate of at least 15 litres/minute.
Siting of troughs
  • Troughs should be sited so that the cows never walk more than 250 meters for water. Any more than this and milk yields will suffer.
  • Siting a trough, sufficiently large to accommodate a ‘row’ of cows, close to the exit of the parlour will also help to meet the peak demand following milking.
  • Ideally the top of troughs should be 85cms (34 inches) above the level where the cow stands. The cow standing should be level, firm, dry and provide no restriction to cow access.
Child safety
  • Water troughs are a potential safety hazard and should never be sited in areas accessed by children.

Whole crop wheat

The successful preservation of whole crop silage depends on making an accurate assessment of the crop dry matter content prior to harvesting. There are two distinct methods for ensiling whole crop:
  • Fermented (similar to grass silage fermentation) whole crop harvested at 35 – 45% dry matter. The majority of the Northern Ireland crop is fermented.
  • Urea treated whole crop harvested at 50 – 60% dry matter. The urea is converted to ammonia in the silo, which inhibits the action of spoilage organisms. Crops containing grass, other green material, or having a dry matter less than 50% are unsuitable and are likely to give a foul smelling unstable fermentation.

When to harvest

The feeding value of whole crop depends on achieving the optimum balance between the increasing starch level in the grain and the decreasing digestibility of the straw during the ripening process. Fermented whole crop should be harvested at 35 – 45% dry matter. The crop colour at this stage is changing from green to yellow and the texture of the grain has changed from milky to cheesy (soft cheddar).
For urea treatment the crop should be harvested at 50 – 60% DM. At this stage the straw will have lost almost all of the green colour, but although firm to touch, you could still split the grain with your thumbnail. With long strawed crops, the starch content can be increased by leaving a longer stubble when cutting.
Finally, check crops on a regular basis as dry matter (ripening) can increase by 1% per day in good weather.

Greenmount Campus herds

Grass covers for the Greenmount Campus dairy herds are recovering following the recent spell of wet weather. 1.5 – 2.0 kg DM of big bale silage has been fed at milking to supplement grass supplies since mid-June. Average grass cover was measured last week at an acceptable level of close to 2500 kg DM/ha for early July. The silage feeding is currently being monitored to see what impact it is having on milk butterfat levels which average 3.83 % across all cows during June.
The herds are being fed to take from maintenance plus 17 to 20 litres from grass depending on pregnancy status, with heifers being fed for maintenance plus 14 to 17 litres. Milk yield is currently 29.0 litres in the High Forage Herd and 28.5 litres in the Premium Milk Herd.

Bulk milk sampling

Dairy farmers should be aware that bulk milk samples collected by their dairies are subjected to testing for brucellosis. Any evidence of brucellosis will result in an extra brucellosis blood test being carried out on their herds. It is in the interest of farmers to arrange to have this blood test carried out as soon as possible when notified by their Divisional Veterinary Office.
If disease is present, then early diagnosis may allow the infected animals to be removed before they infect the remainder of the herd. This could help prevent the loss of the entire herd.
While compensation is paid by the Department of Agriculture and Rural Development for cattle which must be slaughtered to prevent the spread of the disease, it is important to be aware that this does not compensate farmers fully for their loss of capital investment and for loss of income. Indeed, there is no guarantee that compensation can be sustained at its current level, so considerable additional losses may be incurred in the future and farmers are advised to insure against such losses.
While the testing of milk extends our ability to detect disease, farmers should remember that the cardinal indicator of brucellosis is abortion and that every abortion must be reported to their Divisional Veterinary Office.
DARD Farm Management Notes for July 2004 have been prepared by Greenmount Campus, College of Agriculture, Food and Rural Enterprise - Tel: 028 9442 6771. We acknowledge the contribution from Veterinary Service. For further information contact your local Development Adviser.