It might feel like the new yearlings have just arrived at grazing but in less than 6 weeks the bulls will be going in with them, so now is the time to do the final prep. Here are some bullet points to consider:

1. Weigh your heifers

The reproductive performance of replacement heifers is directly related to the live weight at mating and calving. Heifers that do not reach live-weight targets by mating time will calve later and their subsequent fertility will be reduced for future seasons. Well grown heifers also produce more milk in their first lactation, compete better with mature cows and can survive better in the milking herd compared to poorly grown animals.
A heifer’s genetics and liveweight determines when she reaches puberty, not her age. This means that younger heifers can be successfully mated alongside older heifers if they have reached their liveweight target.

• In New Zealand dairy heifers, the best results are achieved when they are at or above 60% of their mature liveweight (LWT) at mating.
• Are the heifers grazing at your property on target to be 60% of mature liveweight by mating time?

LIC offers MINDA weights to their clients as a way of monitoring heifer growth performance using the Breeding Value Liveweight information. This information can be used to help the grazier and owner work together to achieve the best results.

Growth rates frequently fall behind targets during the heifer’s first winter
(9-12 months of age) so regular weighing enables you to assess if the heifers are reaching their LWT targets and if they are not, it enables you to make a plan.

2. Trace elements

Trace elements are important for growth and fertility

Young animals generally do not have large stores of copper in their livers. This means that if they are grazing soils that are low in copper, they do not have reserves to fall back on, and frequently become low.

• Soils high in sulphur or molybdenum can exacerbate this as these elements bind the copper in the soil. This is an extremely common problem in New Zealand.
  Using the right trace element supplements is important
• Copper boluses or multi-mineral boluses are a great option for this class of stock. Boluses slowly release minerals which can provide your yearlings with a steady source throughout the mating period. Selenium and B12 should also be provided, if they are grazing on blocks that have not had selenised fertiliser applied.
• It is important to remember not to use injectable copper within 6 weeks of mating.
  Speak to your Vet about the best way to supplement your heifers, we’re here to help.

3. Bulls

When using bulls there are four critical areas to manage to achieve a high pregnancy rate

Adequate numbers: There should be one bull for every 15-20 heifers. There should also be a minimum for 2 bulls in each mob to limit the risk of an infertile bull.

Healthy: Bulls should be checked daily for ability to serve heifers and observed for injuries or signs of lameness during mating.

Well grown: As with their female counterparts, for optimal fertility, bulls should be 60% of their mature liveweight going into their first mating season. Bulls must start the mating season with a body condition score of 4.5-5.5 and be fed appropriately to maintain this BCS.
Bulls should be vaccinated against leptospirosis and BVD, as well as test negative for BVD.