The non-cycling cow
Non-cycling cows are a common problem in New Zealand dairy herds. They reduce the reproductive performance of the herd as well as the financial performance of the farm.
Non-cyclers are either:
- Cows that have ovulated (i.e. ovaries are ‘cycling') but not shown a heat.
- Cows that have not even started ovulating since calving.
Those cows in the first group may have had a "silent" heat. It has been found that about 80% of cows will not have a heat at the first ovulation after calving. Cows in the second group are described as true non-cycling or "anoestrus cows". This 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. The longer treatment is delayed, the fewer non-cyclers will need treating. However, delaying treatment will also result in a poorer six week in-calf rate and is not effective at treating a non-cycling problem.
Following calving, the first visible post-calving heat should be seen around six weeks provided the cow had an uncomplicated calving. A second heat may occur eight to 12 days later in 30% of cows. After this, heats should be at regular 18-24 day intervals. This is important as cows are a lot more fertile on their third and fourth heats, hence it is ideal to mate to these heats.
Causes of the non-cycling problem:
Calving to mating interval is vitally important but other factors are significant as well, these include:
- Inadequate heifer management. Under-weight heifers have a longer interval to first heat and at least a 10% lower submission rate.
- 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
- More Friesian heifers are treated for non-cycling compared to Jersey or crossbred cows.
- Body condition score (BCS). This is extremely important. Thin cows take longer to start cycling and have lower three-week submission rates compared with cows at adequate body condition scores. It's recommended that cows calve at a BCS 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 BCS 4.0 at mating and cows should be gaining condition. First calving heifers losing excess condition may need preferential feeding or placing on once a day milking. This should be started at least one month before planned start of mating.
- Abnormal calvings and uterine infections. Cows with assisted calvings, twins, caesarians and uterine infections are more likely to be treated as non-cyclers. Metrichecking should be done ideally in four weekly intervals after calving so that cows with uterine infections can be treated early. Herds will need more than one lot of metrichecks and some cows may need two treatments to completely clear an infection. Research has shown that all ‘at risk' cows should be treated with a Metricure®, and the sooner, the more likely they are to conceive.