Non Cycling Dairy Cows

What are NVO's?

Non cycling cows also known as No Visible Oestrus (NVO) cows are a common and frustrating problem on most farms.

A period of noncycling called "anoestrus", following calving is normal and cows start coming on heat as the uterus recovers from pregnancy and reduces in size. Most cows will start cycling within 40 days of calving, assuming adequate nutrition and body condition. The cow will then come on heat every 21 (18-24) days until pregnancy occurs.

Conditions that prevent cows coming into heat post calving include:

  • Inadequate nutrition pre and post calving.
  • Any chronic debilitating disease process, such as uterine infection "metritis", left displaced abomasum and lameness
  • Any other cause of excessive weight loss.
First calving heifers usually take longer to start cycling activity due to the nutritional stresses resulting from continued growth and lactation, and often make up a major proportion of NVO's.

The veterinary examination and treatment of cows that have not been mated after one round of AI is a common and accepted procedure. Cows that have shown no sign of heat in the first 20 to 30 days of the mating period should be examined by a veterinarian, provided they have been calved for at least one month. In most cases this allows time for the treatment to work and the cow to be submitted for AI.

At this examination these cows will fall into one of the following groups:

  • Pregnancy
  • Uterine or ovarian pathology
  • Corpus luteum (CL) present
  • Active Ovaries
  • Small inactive ovaries
Uterine or ovarian pathology
Disease associated with the reproductive tract. Examples of some of these conditions include; pyometra, endometritis, or cystic ovaries. We are usually able to treat these conditions to get the cow cycling.

 

CL present
These cows may have been cycling and have not been detected, or may have had a silent heat. An injection of prostaglandin (PG) will bring these cows on heat in 2-7 days. Remember that normal heat lengths can be as short as 3 hours. Heat detection aids such as tail paint and KAMAR heat detectors are very useful, especially for cows that have quick heats.

 

Active ovaries
These cows may have already cycled (without showing heat) or they are about to cycle. Most only need more time and should cycle in 2-3 weeks. Again the heat detaction aids are very helpful for detecting these cows.

 

Small Inactive Ovaries
These are true anoestrus cows. Nutrition, lameness or illness are important common causes of anoestrus. After investigation of the causes for anoestrus and necessary treatment, these cows can be inserted with a CIDR and an injection of oestrogen.
This results in a very high percentage of anoestrous cows showing heat after CIDR removal.

Trial results have shown that some cows that fail to conceive do not come back on heat. This problem can be overcome using reinsertion of the used CIDRs (used but cleaned before reuse) and re-treatment with oestrogen. Re-treatment of anoestrous cows, is a low cost option that is worth considering.


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Benefits of Early Treatment

The In Calf project, (originally known as the National Dairy Herd Fertility project) has confirmed and reinforced the fact that later calving cows have substantially reduced fertility compared to their earlier calving herd mates. It is these later calving cows that make up this bulk of the group of NVO's. If we do nothing, many of these cows end up empty, or as late cows in the following year.

 

    There is good evidence that early treatment of NVO cows results in:

  • Increased numbers in calf to AI.

  • Less empty cows.

  • Fewer cows to induce in the following year.

If heats are recorded before MSD, NVO cows can be treated prior to MSD. This will mean that approximately twice as many cows will be examined, however, this gives the true non-cyclers a chance to be mated twice in the first 30 days of mating. The In Calf project results show that these early treated NVO's have fertility that is almost equal to their non treated naturally cycling herd mates.

The earlier that NVO's are identified, examined and treated, the better.


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Prevention of NVO's

  1. Grow out heifers well and join them to start calving at the start of the calving period or even a couple of weeks before.
    2.  
  2. Use Heat Detection aids throughout the entire joining period to minimise missed heats.
  3. Identify and treat NVO's early in the AI period.
      4. There are two strategic times that treatment can be targeted.
    • Prior to Mating Start Date (MSD):
      This requires heat detection commencing about 30 days before MSD. An easy way to do this involves use of tail paint with twice weekly recording and topping up. If a different colour is used on cows that have cycled the NVO's can be readily identified.
      Cows can be treated in the week before MSD so they will be cycling in the first week of AI.
    • After one "round" of AI:
      This allows all cows to have a chance to be detected on heat say 21-24 days after MSD or earlier in herds that have synchronised.
  4. Plan inductions well in advance. See the
    5. induction page for more information.

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