LIC | Leave no cows behind at mating time!

Leave no cows behind at mating time!

Good heat detection helps you get:

  • More cows in calf quicker
  • A tighter calving spread 
  • More days in milk

LIC is sharing the following information to help farmers ensure they get enough quality replacement heifers for their herd for the long run.

A compact calving is important for creating sustainable herd fertility. To get a low empty rate with a 10-12 week mating period, many herds need to get more cows in calf quicker.

However, with the national 3-week submission rate stalled at 77%, more than one in five New Zealand dairy cows are ‘left behind’ during the first three weeks of AB!

These cows don’t get a chance to calve early to AB the following year. Calving pattern slippage puts them at risk of reduced ongoing reproductive performance and contributes to a spread-out calving pattern. 

Calving pattern is very important. As stated in The InCalf Book “a better calving pattern gives better reproductive performance”.

With mating fast approaching we have a golden opportunity to identify and help cows that could otherwise end up left behind this year.

Cows not submitted in the first three weeks of mating:

  • Are less likely to produce an AB replacement the following season
  • Usually have fewer chances to get in calf 
  • Are more likely to go empty than their cycling herd mates, and
  • Will produce less early-season days in milk and less profit than if they calved in the first three weeks of calving next season

But it’s not the same for every herd. Cows in the top 25% of herds on submission rate have a 12% greater chance of being mated in the first three weeks.

So who could be left behind?

  • Cows that are cycling but were undetected – missed heats will account for some
  • Cows that deliberately aren’t mated to AB or have had unrecorded natural matings
  • Non-cycling (anoestrous) cows are likely the biggest group in many herds (14-19% of the herd in some studies)

"The best heat detection results are achieved by combining paddock observations with heat detection aids such as tailpaint and heat mount detectors" - DairyNZ InCalf Book.

Anoestrous cows need help and they need it early! Chances are a significant proportion of them are good young cows that should be kept as early calvers in the herd for years to come. Risk factors for anoestrous include: 

  • Thin cows (body condition at calving is one of the strongest drivers of how long it takes for cows to resume cycling after calving)
  • Young cows (especially if undergrown) 
  • Sick cows
  • Late calving cows

Act early to leave no cow behind! 

The earlier you identify cows at risk and intervene, the fewer will end up missing in action:

  • Identify at-risk groups - use MINDA reports to help identify the at-risk group in your herd. LIC staff or your vet/consultant can help
  • Identify individual cows – monitor pre-mating heats. Apply heat detection aids such as tail paint or Bulls-i’s five weeks out from mating start date. (Use the annual planner at
  • Intervene early - talk to your vet and LIC representative to make the plan to get them cycling, mated and to cover the returns

Consider the options

Doing nothing or delaying treatment can be a costly option, so plan ahead carefully and seek professional advice.

  • Effective options are limited largely to hormonal intervention close to mating start date; discuss the options with your veterinarian 
  • Earlier intervention almost always works out the best for return on investment. Leaving it too late can result in an overall loss; chat to your vet
  • Once-a-day milking (OAD) for 10 weeks from calving has been shown to have reproductive benefits, while a study investigating the  impact of OAD milking 7 days prior to mating start did not influence days to conception
  • Don’t rely on bulls ‘bringing them on’. While bulls are excellent heat detectors, there is no scientific evidence of a ‘bull effect’ that brings dairy cows on heat
  • Hormonal treatments do not address the underlying causes of prolonged anoestrous, so management changes such as improving body condition at calving should also be investigated

Don’t leave it to chance with your herd this spring. Monitor pre-mating heats now, talk to your rural advisors and put a plan in place that works best for you. 

Give those cows every chance to calve early for you next season.


1. DairyNZ (2007), The InCalf Book for New Zealand Dairy Farmers, p 150. DairyNZ: Hamilton, New Zealand.
2. Phyn, C. (2016). DairyNZ. Personal communication.
3. Dalley, D., Clark, D., and Bateup, N. (2007). Reproductive Performance of Cows Milked Once a Day (OAD). Proceedings of The Once-a-Day Milking Conference, 1: 9-13
4. Rhodes, F. M., Clark, B. A., MacMillan, K. L., and McDougall, S. (1998). Use of once daily milking or treatment with progesterone and oestradiol benzoate in anoestrous cows. Proceedings of the New Zealand Society of Animal Production, 58: 44-46.
5. Rhodes, F. M., McDougall, S., Burke, C. R., Verkerk, G. A., and Macmillan, K. L. (2003). Invited Review: Treatment of Cows with an Extended Postpartum Anestrous Interval. Journal of Dairy Science, 86: 1876-1894.



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