Tightening your calving patten – Is PG synchrony the right fit?

Tightening your calving patten – Is PG synchrony the right fit?
By Margaret Perry, Veterinarian, Anexa Vets Te Aroha

Days in milk is one of the biggest drivers of production and a tight calving pattern is one of the key influencers of your reproductive performance. Have you sat down recently (at an appropriate social distance) with your Anexa veterinarian to determine what the best plan is for your herd’s mating? If not, get in touch with them – we’re talking all things repro these days!

Managing your non-cyclers

The first step in tightening up the calving pattern is identifying whether non-cyclers are going to damage your submission rate. To identify the non-cycler group, we recommend tail painting cows five weeks before the planned start of mating (PSM). This gives us enough time for a complete cycle plus time to initiate treatment before the start of mating if required. Cows are suitable for non-cycling treatment once they have been calved for just three weeks.

The first step is to identify if there is a problem in your herd. If more than 15% of your herd are ‘non-cyclers’ 10 days before the start of mating, this will have a negative impact on your calving pattern. We can reduce this impact with early intervention.

The second step is identifying the best method to deal with your non-cyclers. Your vet can work through a return on investment calculator to determine the program that suits your herd best. When non-cycling cows are treated nine days before the PSM, they will calve 16 days earlier than if no CIDR intervention had been done.

Managing your cycling cows

Another popular way to tighten your calving pattern is to use PG or ‘why wait’ synchrony to ‘short cycle’ cows. This form of synchrony is only useful in cycling animals and is relatively cheap. If you have addressed your non-cyclers or do not have a non-cycling problem, then synchrony might be a good tool to use to condense the front end of your calving pattern.

There are several factors to consider when contemplating PG synchrony.
  • Can your farm cope with having large number of cows on heat? Large mobs of cycling cows require extra feed in the days leading up to peak heat and if conditions are wet there can be significant pasture damage with large numbers of cows on heat all at the same time.
  • How is your heat detection? Different to a CIDR program, PG synchrony programs require that you and your staff be geared up to detect standing heats in the days following the PG injections. Most cows respond within 2-5 days post treatment, so you and your team need to be ready and able to heat detect and draft large numbers of cows for AB.
  • Are your AB facilities set up to inseminate large numbers of cows in a time efficient manner? You need to make sure your AB company is informed about your program and that extra technicians can be sought so technician fatigue does not become a problem.
  • How is your mating placed to respond to the synchronised cows’ return cycles? The synchronised cows that do not hold to their first insemination will return 18-24 days later and then again 36-48 days later if not holding to the second insemination. Will AB still be going or will there be enough bull power to cope with a large wave of return matings?
  • Are you set up to manage a rapid calving next season? Is your farm set up to adequately feed an increased number of early calving cows? Do you have enough staff to cope with calving large numbers of cows? Will the calf rearing crew cope? Colostrum collection and delivery is crucial in making sure this early group of replacement calves get the best start.
Your vet is ready to talk through whether PG synchrony suits your system and calving pattern needs. There are many herds we work with that are doing these programs year-on-year with success, talk to your vet to make sure PG synchrony suits your system.



Date Added: Thursday, 3rd September 2020


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