Restricting feed as cows approach calving helps mobilise the animals’ body fat. Glenys Christian reports.

Transition cows don’t need a complicated diet and feeding them can be simple, DairyNZ researcher, Jane Kay told the Northland  Agricultural Research Farm (NARF) field day at the end of May.

She stressed to farmers attending the benefit of slightly restricting cows’ feed as they approached calving to around 90% of their requirements.

“The animal starts to mobilise a bit of body tissue,” she said.

“It uses that fat so the liver is all primed up and ready to deal with the situation post-calving.”

If this didn’t happen fatty acids were not mobilised, she said.

“It’s like training for a marathon rather than walking to the beer fridge.”

‘It’s like training for a marathon rather than walking to the beer fridge.’

Fat cells released the hormone, leptin, telling the cow it had enough energy and didn’t need to go out and get more. The feed restriction worked exactly the same in a pasture-only situation or where cows were fed a total mixed ration (TMR) with blood calcium levels increasing on the day of calving and the day after, reducing the risk of milk fever.

Kay said magnesium was the most important mineral in the prevention of milk fever and cows needed a daily supply for one month before calving as well as four months after giving birth. The recommendation was 20 grams down the throat with research carried out at Number 2 Dairy at Ruakura Research Station in the 1980s showing a huge impact on milk fever.

Calcium levels needed to be kept as low as possible before calving then cows should be supplemented after birth as there was a 400% increase in demand.

Kay detailed trial work carried out by Dr John Roche, when he was DairyNZ’s principal scientist, animal science, feeding a grade of zeolite, a spongy clay substance before calving, which sits in the rumen. A different grade of zeolite is used in the making a kitty litter which absorbs iron and holds ammonia. Results showed higher calcium levels and lower magnesium and phosphorus levels with a cost of around $30 a cow.

“Watch this space,” she said.

Successful transition checklist

  • Ensure cows are on track to achieve body condition score (BCS) targets at calving.
  • Feed cows appropriately before calving.
  • Supplement all cows with magnesium before and after calving.
  • Maintain low calcium before calving and supplement all colostrum cows with calcium.
  • Avoid feeds high in phosphorus such as palm kernel and supplement if feeds are low in phosphorus.
  • Avoid grazing pastures high in potassium.
  • Understand dietary cation-anion difference (DCAD) in a grazing system.