Heifer AI.

When deciding on whether or not to join the yearling heifers to AI there are a few factors that should be considered.

Firstly, why artificially inseminate heifers?

The benefits of AI joining the heifers include:

  1. Increased rate of genetic gain.
  2. Synchronisation of heifers without the need for extra bulls. 90% of treated heifers will cycle within 24 hours. The benefits of an intense mating and calving pattern might be the reason for a synchronising program. If natural mating is desired a program can be staggered over several days.

The disadvantages of heifer AI:

  1. Reduced calving rates to AI compared with natural mating. One survey of heifers showed that higher percentage of naturally bred heifers calved within 21 days (67%) compared to those synchronised and joined to AI (55%).
  2. Increased calving difficulties in friesian heifers mated to friesian sires. Although a great deal of attention has been put into achieving satisfactory calving weights and the search for ease of calving sires, it is difficult to achieve easy calving for all friesian heifers joined to friesian sires compared to jersey sires.
  3. Losses associated with calving difficulties in friesian heifers mated to Friesian sires. Some calving difficulties can be minimised by good heifer managemnt. However, problems are still experienced by many farmers. The losses include decreased first lactation production due to trauma, poor reproductive performance in following seasons and loss of heifers due to calving paralysis.