Poor fertility performance is a widespread problem in dairy herds throughout the world.
The situation in Northern Ireland is no different with an average calving interval of more than 400 days and cull rates in dairy cows of 7.5 per cent due to infertility.
Fertility is one of the major factors affecting the efficiency of any dairy herd. It can account for one of the main costs of production and can also represent an area where significant improvements can be made.
Poor dairy fertility is recognised as having many consequences, both direct and indirect. Most importantly:
- Loss of milk production through too many dry days or peak yield traded for later lactation yield.
- Disruption to the calving season and milk production pattern.
- Loss of mature cows due to additional culling for poor fertility.
- Extra veterinary costs.
- Reduced calf sales.
- Additional AI costs.
- Enforced culling resulting in more replacements being reared or bought.
- Reduced or slower genetic improvement.
- Subsequent disease effects due to metabolic problems or nutritional imbalances from prolonged lactation or dry period.
There are two main trends in dairy fertility that have the highest impact on overall performance:
- Fewer cows are seen in heat when they should be bred (45-60 DIM). These cows would benefit from maximising submission rates.
- Fewer cows are detected as pregnant after service. In these cows the aim is to improve pregnancy rates.
The relationship between poor fertility and negative energy balance in freshly calved cows has been well documented.
In order to improve fertility in dairy cows farmers should pay attention to the management of transition cows and aim to reduce negative energy balance in early lactation cows. Body condition scores at drying off should range from 2.75 to 3 and body condition scores at calving from 3 to 3.25. Ideally less than 10% of cows should suffer a loss of body condition scores of more than 0.5 units in early lactation and body condition scores at breeding should be a minimum of 2.75.
Improvement of submission rates can be achieved through improved heat detection or by using breeding protocols to ensure eligible cows are served. Taking control of the cows’ oestrus cycle provides many advantages, such as targeted oestrus detection, fixed time AI which is taking away the need for oestrus detection, handling of animals in batches which should allow easier AI, pregnancy testing and observation around calving. Other advantages include the access to sires with maternal traits suitable for producing dairy heifer replacements and increased milk production by increasing the number of productive days in early lactation.
Improving heat detection and pregnancy rates in high yielding dairy cows can be achieved through the use of breeding protocols.
High producing dairy cows commonly have a lower progesterone level which affects their fertility. As high yielding dairy cows are on a much higher plane of nutrition their liver will metabolise sex steroids such as progesterone and oestrogen at an accelerated rate.
Therefore breeding protocols based on progesterone devices such as CIDR® are particularly useful in these cows. Using breeding protocols based on CIDR® can help heat detection through stronger signs of heat or allow for fixed time AI. Increasing progesterone before timed AI can result in a substantial improvement in fertility (more than 10%), suggesting that the reason for lower fertility in lactating dairy may be at least partly due to reduced progesterone concentrations during the time period before AI.
In addition, the use of GnRH (Acegon®) at insemination significantly increases the overall probability of pregnancy by 12.5 % in treated cows. When used on repeat breeders the probability of pregnancy was increased up to 22.5%. A second injection of Acegon® can be given 12 days after AI to increase progesterone levels in early pregnancy which is associated with better embryonic development and overall higher pregnancy rates.
With the cost of each additional day on the calving interval varying between £2-£5 per cow in most herds, farmers should get a return on their investment by using breeding protocols to ensure cows are bred in time.