Applying Incalf Results to Your Herd Today
One of the messages from the Incalf project was to confirm that reproductive performance of dairy herds depended on events and management decisions that occurred throughout the year, not just during the joining period.
This months Incalf article will address one of the important findings from the project and suggest ways of utilising the information in your herd.
In a seasonal calving herd the planned start of calving (PSC) is 282 days after mating start date (MSD). We used to believe that cows that had been calved at least eight or so weeks prior to mating were about as fertile as they could get. What the study showed was that the advantages of early calving were even more important than previously thought.
Early calving cows are significantly more fertile than late calving cows.
There are 12 weeks between PSC and MSD. In table 1, the first group of cows consists of those that calved in the 1-2 weeks prior to PSC. As can be seen these cows were even more fertile than the group of cows that calved in the first three weeks after PSC.
| Calving Group | 6 week in calf rate | Empty Rate | 21 Day Submission Rate | First Service Conception Rate |
|---|---|---|---|---|
| Before PSC | 76% | 4% | 89% | 57% |
| Weeks 1-3 | 71% | 5% | 84% | 53% |
| Weeks 4-6 | 62% | 8% | 75% | 46% |
| Weeks 7-9 | 51% | 11% | 62% | 38% |
| After Week 9 | 22% | 19% | 20% | 26% |
For later calving cows the penalties in terms of fertility are even more significant.
If high fertility is one of your goals then aim to calve as many cows in the first few weeks after PSC as possible.
If a significant portion of the herd calves late ie after week 6 of the calving period, high fertility is very difficult to achieve.
What can be done now?
- Assess heifer performance.
- Heifers are the group of cows whose calving dates are easiest to manipulate. If heifers are well grown and mated to bulls of good fertility it is possible to have 70% calved in the first three weeks and 95% in six weeks. So, weigh heifers. Aim to have Friesian heifers at 350kg body weight at joining and Jersey heifers at 280kg. If they are below these targets now, start proceeding to correct this deficit ie worm control and nutrition. Perhaps consider joining heifers 1-2 weeks prior to cows.
- Plan induction program
- One of the key findings of the study was that induction did not affect reproductive performance.
This meant that cows that were induced to calve early in the calving period had quite good performance. Those that were induced to calve late in the calving period had poor reproductive performance, but no worse than a non induced cow that calved at the same time. - Plan induction program
- So if you choose to induce cows they should be induced as early as possible. Cows can be induced up to 10 weeks prior to their expected calving date.
In order to do this we need to know when their expected calving date is. This can be done using accurate and sustained heat detection and returns or non returns to service as indications of pregnancy.
Early pregnancy testing ie 12-15 weeks after MSD allows you to very accurately determine which cows are definitely in calf to AI and which cows are definitely not.
A planned approach to early induction involves:
- Accurate expected calving dates.
- Planning of dates for induction.
- Early drying off. Cows need 7-8 weeks dry period before induction.
- Special attention if necessary to the "to be induced" mob.
Click here to view the rest of the 1999 November newsletter.