In the last two weeks I have fielded a lot of questions about breeding heifers and synchronising them. Everyone knows the importance of calving down heifers before 24 months and breeding them at adequate body weight at around 13-15 months. The average weight, depending on breed, should be around 330kgs.
This is undoubtedly an area where farmers can reduce expense by having heifers calving down early and breeding at the correct weight and age. There are several different management options as MSD (mating start date) approaches. Heifers should receive tail paint and observe for heat provided they are cycling. Heifers will be cycling, provided nutrition is correct and genetics are on their side. To enhance SR and to speed up the process, we often employ synchronisation techniques on the farm.
Before discussing synchronisation, we must look at the reproductive cycle to understand why we use certain agents. The most common question I get asked is about the bulling injection or prostaglandin (estrumate, lutalyse). This will bring heifers around or into heat only if they are cycling first and if there is an active functioning CL (corpus luteum) present in the average 21 day cycle.
Standard 21 day cycle
So therefore prostaglandins (PGs) such as estrumate are only effective between day 5-17 generally and you will have up to 9-10 days of the cycle where giving them PGs has no effect on that cycle. This is where the strategic protocols have been developed to get heifers in heat using PGs. There are three options I apply on farms with heifers using PGs. Whichever one you use can be in relation to time and labour or cost. This should be done in consultation with your own vet.
By adopting these protocols, we allow more controlled breeding and even those heifers missed will be repeating at more regular intervals for the rest of the breeding season. Of course there are more sophisticated and expensive techniques; your own vet will help you manage these. The important message is if using prostaglandins, heifers must be cycling and they are only active when a functioning CL is present.