Nantglas Project Update – Improving fertility in a split block calving herd

Spring calving has come and gone at Nantglas farm in Talog. The planned start of calving was 28 February, however, calving actually started on  23  February and finished on 22 May. This was effectively 12 weeks of calving with only 2% losses. 

Prior to calving, Rupert from ProStock veterinary practice retrieved blood samples from 10 cows of the dairy herd to check for trace element/mineral deficiencies. Fortunately, results showed no significant deficiencies present proving that the farm's mineral supplementation regime is effective.

Iwan and Rupert have also been Metrichecking all cows to identify if any has endometritis, which is a bacterial infection of the uterus. No issues were seen and a low number of dirty cows recorded. 

81% of the herd calved within the first six weeks allowing Iwan to sell eight late calving cows (7% of the herd) which will tighten the calving block next year. The culling of late calvers increased the six-week calving figure to 90%.

Alta collars were installed on the spring calving herd on 12 April which started detecting heat by the tenth day. Below are some screenshots of the collar dashboards from 22 May, showing three cows were showing signs of heat. It also showed that one cow needed attention. This has significantly helped Iwan in data collection and minimise costs such as fertility treatments. It also allowed for resource efficiency improvement including labour and AI. Iwan still uses tail paints alongside collars as a safety net approach, especially during the grazing seasons. For example, cows breaking out of electric fencing can confuse cow activity on the collars. 

Kate Burnby, the specialist working with Iwan, put together a mating plan, aiming to synchronise the cows and heifers. First service was calculated for 20 May. High submission rates are key to achieving a tight calving pattern. Heifers were injected with prostaglandin (PG) and tail painted.



Iwan has reported a 92% three-week submission rate in the first round of service, but only PD (pregnancy diagnosis) will show the true results and pregnancy rates. Going forward, Iwan will be scanning all the cows and heifers and we will await the results.
Autumn calvers are now dried off, with some low yielders dried off early due to the lack of grass growth in June. The Alta collars will be taken off the spring calving herd and re-set for the autumn calvers to minimise the cost of hire. Calving is set to start on 21 August and Iwan will be keeping detailed calving records that will help Kate terminate a plan for the autumn calving herd and reduce the calving block.






Mating Plan:


Heifers - bunch of 30

  1. Vet visit and inject prostaglandin to the heifers on Monday 11 May. 
  2. Serve to observed heat 2-5 days after injection.  The expectation is that most will be put-up on the Thursday/Friday that week. Expect approximately 20 to be served after this injection.
  3. On Monday 18 May, inject prostaglandin to any heifers that have not been served (likely this will be 7 - 10 animals) and serve to observed heat over 2-5 days.
  4. Introduce bulls on 23 May.


Cows - pre-mating heat detection and clean checks

  1. Recheck any positive Metricheck cows next week and infuse Metricure if grade 2 or higher.
  2. On 12 May, identify any cows that did not heat in the previous 24 days
  3. Vet to visit on 13 May to examine non-cyclers. If they’re clean and more than 30 days calved then synchronise with CIDR program so they will then be served in the first week of mating.


Planned start of mating (PSM) 20 May - there will be 30+ cows/week to serve