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Non Cyclers

Non cycling cows are a problem in any dairy herd.  They reduce the reproductive performance of the herd and consequently reduce the financial performance of the farm.

There are two types of non-cyclers:

  1. 1.Cows that have ovulated (i.e. ovaries are ‘cycling’) but not shown a heat.

  2. 2.Cows that have not even started ovulating since calving, and cannot have a heat.

Those cows in the first group may have had a “silent” heat. It’s been found that about 80% of cows will not have a heat at the first ovulation after calving. The cows in the second group are described as non-cycling or “anoestrus”.  This type is the most common form of infertility in New Zealand herds.

Most herds have some non-cycling cows that need treatment each year. These may be treated either before the planned start of mating or after mating has started.  If treatment is delayed, fewer non cyclers will be needing treatment. However, delaying treatment will also result in poorer 6 week in-calf rate and is not effective at treating a non cycling problem.

After calving, the first visible post-calving heat should be seen within 6 weeks provided the cow had an uncomplicated calving. A second heat may occur 8 to 12 days later in 30% of cows. After this, heats should be regular at 18-24 day intervals. This is important as cows are more fertile on their 3rd and 4th heats and hence it is ideal to mate to these heats.

Factors involved in a non cycling problem:

Calving date important but other factors are significant, these include:

  1. Inadequate heifer management. Under weight heifers have a longer interval to first heat and at least a 10% lower submission rate.

  2. Young cows. First calving heifers need an extra 10 days to start cycling compared with an older cow. This is the reason why you should mate your 15 month replacements a week or two before the main herd. This should help reduce the number of first calving heifers being treated.

  3. Friesians. More Friesian heifers are treated for non-cycling compared to Jersey or crossbred cows.

  4. Body condition score. This is highly important. Thin cows take longer to start cycling and have lower 3 week submission rates compared with cows at appropriate body condition score.  It’s recommended that cows calve at a body condition score of 5.0 and heifers at 5.5. Body condition loss from calving to mating and condition score at mating also affect the incidence of non cyclers. There should be no more than 15% of cows below body condition score 4.0 at mating and cows should be gaining condition. First calvers losing excess condition may need preferential feeding. This should be started as soon as possible.

  5. Abnormal calvings and uterine infections. Cows with assisted calvings, twins and uterine infections are more likely to be treated as non-cyclers.  Metrichecking should be done ideally by 4 weeks after calving so that cows with uterine infections can be treated early. Herds may need more than one lot of metrichecks and some cows may need two treatments to clear. Recent research is starting to show that all ‘at risk’ cows should be treated with a Metricure, whether a visible infection is present or not.

How to identify non- cyclers:

A well designed pre-mating heat detection programme is the best way of identifying non-cycling animals. The use of tail paint or heat mount detectors (or both) can be an effective way of identifying animals that are cycling.

Ideally all cows should be tail painted with Colour 1, 5 weeks before the planned start of mating. As cows loose their tail paint they should be painted Colour 2. By 3 weeks after first tail painting, any animals that still have the original tail paint colour are non-cyclers and require treatment in order to meet the planned start of mating target date.

Treatment of non-cyclers:

Treating non-cycling animals will mean they calve earlier the following season resulting in a longer lactation with higher production as well as a longer interval from calving to mating to gain body condition score. Early treatment will increase submission rate and help these cows get in calf earlier. Addressing the factors involved in non-cycling problems will help reduce the number of non-cyclers the following season. As the rate of allowed inductions is dropping, and inductions may be banned completely in future

Treatment protocols

Coming soon

(References -The Incalf Book for NZ Dairy farmers)

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