1) Managing cows during AB
If you aren’t too sure if a cow is on heat or not, draft her out and observe her with the other cows on heat. It will become clearer whether she is on heat (if she is being ridden by other cows), or not (if she isolates from the other cows) – in which case refresh her heat detection aid/s and return her to the paddock.
It is also important to return the cows which have been drafted out back to the paddock after mating. It is these cows who will help identify the cows coming into heat ready to be mated tomorrow!
2) Submission rates
The 3-week submission rate is a key driver of the 6-week in-calf rate. Three weeks is long enough for most cows to have cycled once. Therefore, the target 3-week submission rate is 90% - this equals about 4% of cows submitted per day.
Check your submission rate on the daily graph in MINDA® Live (reproduction section, mating tab) to see if you’re on track. You should be hitting about 30% submission rate at the end of the first week of mating.
If you’re not on track, you are still early enough into the mating period to make changes. Taking this opportunity to ensure heat detection is optimal is paramount. If that is not where the problem lies, seeking help to identify what else is affecting performance is recommended.
3) Short returns
The majority of cows will have an oestrous cycle every 18-24 days (there is a small chance of a true heat outside this period). Keeping an eye on the number of cows that have returned to heat between day 1 and 17 is an indicator of the accuracy of heat detection.
To help you with this, take note of the Early Indicator – Repeat Matings graph on MINDA® Live during the first 17 days of mating. You want to keep this below 10%, but don’t panic if you get into double figures - use it as a chance to review your heat detection practices.
4) Heat detection aids
Heat detection aids are great at assisting with heat detection throughout the AB period - they can help with making sure the cow is really on heat.
There are many types of aid you can use including tail paint and heat mount detectors. These aids are far more helpful when maintained and read correctly.
Photos: Heat mount detector, LIC (left); Tail paint, Dairy NZ (right)
Maintaining your heat detection aids throughout mating, as recommended by the manufacturers, is especially important as the mating progresses. Make sure your staff are up to scratch detecting heat and consider using a second aid to help with lengthy mating periods as the number of cows returning to heat lessens.
For more tips on heat detection aids check out page 111 in the InCalf Book (Chapter 13). All of the aids have pros and cons, so it’s a matter of working out what suits your farm routine, budget, and goals.
5) Nutrition – milk dockets and body condition score
Nutrition plays a huge part in reproductive success. Watch your milk dockets for a drop in milksolids production (0.007-0.01 kg/cow/day) over a period of 2-4 days. This may indicate that pasture quality is declining, and cows are getting less energy.
Regularly checking the body condition score of your cows will also give an indication of whether they are getting enough energy. Cows shouldn’t be dropping more than 1 condition score between calving and mating. A drop of more than 1 condition score can negatively affect the submission rate and conception rate of your herd. The Dairy NZ condition score targets are 4.5 for 2- and 3-year old cows, and 4 for cows older than 4-years old.
Decreasing the energy demand and/or increasing energy supply may be beneficial to manage a decline in nutrition around the mating period. Ways to achieve this may include once-a-day milking, supplementary feed, adjust paddock rotation to manage pasture covers.
For more information check out the InCalf Book (Chapter 11).
6) Bull management
For many farms there will be bulls already on the property, whether they are being used over heifers, over cows after AB, or both. Making sure you have enough bull power to service your cows is key to reproductive success.
Dairy NZ guidelines suggest a ratio of 1 bull to 20 heifers, and 1 bull to 30 non-pregnant cows. With additional bulls on hand in order to rotate bulls in and out of the active team, and particularly to cover injury and fatigue of active bulls.
If you are synchronising your heifers you may need a larger bull team to cover more heifers coming into heat over a shorter period. Similarly, if synchronising your cows and the cows are due back on heat within the natural mating period, you may also need more bull power for that period.
For more information on bull management, check out the InCalf Book (Chapter 15).
For more information or help with your heat detection, contact your local rural professional or InCalf advisor.