NEW ZEALAND - Adding condition to a cow requires feed and time, with many New Zealand farmers not drying off early enough.
This is according to Dr Jane Kay of Dairy New Zealand who is advising Kiwi dairymen to afford their cows more time to gain body condition score (BCS) units.
Autumn is fast approaching in New Zealand and many southern hemisphere herds are being prepared for winter forage grazing.
“The main objective of management in the last third of lactation is to set the cow up for the following lactation,” said Dr Kay. “This requires a focus on body condition score.”
“To optimise milk production, reproduction and health, mature cows should be BCS 5.0 at calving, with first and second calvers at 5.5 BCS1.”
She added that greater susceptibility to infectious and inflammatory disease is reason enough to taper milking and boost feeding to avoid thin cows.
She laid out four ways to do this:
- Increase feed allocation to lactating cows
- Once-a-day (OAD) milking
- Dry off at-risk cows early
- Feed dry cows for BCS gain
However, she warned farmers that, at this stage of the season, the first two options were too little too late.
Dr Kay said: “Increasing feed allowance or supplementing lactating cows has only a small effect on BCS gain, because genetic selection over several decades has resulted in cows that partition energy to milk at the expense of BCS.”
Dry cows gain BCS far easier than lactating cows as energy is not being required to produce milk and their activity rates are lower.
However, Dr Kay cautioned farmers that nutritional content of feed and the duration of the dry period have a huge say on BCS going into calving.
Outlining the nutritional demand for a 450 kilo cross-bred cow for a pasture/silage and a pasture and palm kernel extract diet, she said: “If dried off at 90 days pre-calving, she has approximately 50 effective days to gain one BCS unit.
"This means that at eight weeks pre-calving, if she was fed pasture and pasture silage, she will need to eat 9.3 kg DM/day in total.
“In comparison, if this cow is milked for longer and dried off at 60 days pre-calving, at eight weeks she will need to eat 13.7 kg DM/day.”
A dry period – on Dairy NZ’s feed assumptions - must be at least 90 days in order consume enough energy, Dr Kay concluded.
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