Excellent herd reproductive performance is one of the most important factors to maximizing herd profit. Table 1 shows how much net return per cow increases with increasing pregnancy rates. The reason is that improving pregnancy rate affects many areas of the dairy. These are the reasons higher pregnancy rate improves herd profit:
- Keeps days in milk (DIM) in the optimum range. Ideally DIM should be 150 to 170. Lower DIM means a higher percent of cows are in early lactation resulting in higher milk production. For every 10-day reduction in DIM, milk production will increase 1.2 to 1.7 pounds per cow per day. Whole herd feed efficiency will increase because of the higher milk production.
- Less reproductive culls. Culling cows because they do not become pregnant in a timely manner is the biggest reason for culling in most herds. Decreasing the number of cows culled because of reproduction allows producers to cull more cows for low production.
- Increases in the number of calves born. This results in more bulls to be sold. The extra females improve replacement option flexibility such as culling low genetic heifers or increasing whole herd cull rates.
- Less over-conditioned cows at calving resulting in lower incidence of transition cow disorders.
- A lower percent of cows with a high number of days dry.
Every herd should set a goal of having a pregnancy rate of 20% or greater. Many herds are achieving pregnancy rates of 23 to 25%. By understanding the factors that affect pregnancy rate we can examine our records and develop a plan for improvement. Pregnancy rate is simply the percent of cows eligible to be bred that actually get bred multiplied by the conception rate of those inseminations in any 21-day period of time. A 21-day period is used because that is the average length of a cow's estrus cycle.
Here is an example:
- Fifty open cows are eligible to become pregnant (beyond the voluntary waiting period)
- Thirty cows actually are inseminated (30/50 = 60% submission or service rate)
- Twelve of these cows become pregnant (12/30 = 40% conception rate)
- For this 21-day period, the pregnancy rate is 12 pregnant cows/50 eligible cows or 24%
- Another way to calculate the pregnancy rate is 60% x 40% = 24%
First let's examine the factors that affect service rate. The list is not very long. The biggest factor is how fast cows are bred after the end of the voluntary waiting period. Improved heat detection or a timed AI program will increase this. The reason timed AI programs often improve pregnancy rate is that 100% of cows are bred shortly after the end of the voluntary waiting period. The next biggest factor is the ability to identify and re-inseminate open cows rapidly. The best herds have systems in place that identify open cows through estrus activity at the first estrus cycle following insemination. Some herds do frequent herd checks to identify open cows and re-enroll them in a synchronization program. It is difficult to achieve high pregnancy rates without re-inseminating open cows in a timely manner.
Solving a low conception rate can be a little more challenging. The most likely culprits of low conception rates are poor compliance with synchronization programs or a poorly designed synchronization program, low energy status in the cows resulting in a high percent of cows that are not cycling, and poor transition cow programs that result in cows with below optimum fertility. Other less common problems include poor vaccination programs, low sire fertility, and improper handling and placement of semen.
To achieve a high pregnancy rate, target for a goal of at least 65% service rate and 35% conception rate. Another good goal would be to cull less than 5% of the total herd for reproductive reasons.
Achieving good reproduction is an attainable goal for all dairy farmers. If your reproductive program is less than desired, work with your management team to identify areas to improve and develop an action plan for improvement. The resulting changes will greatly improve your herd's profitability.
Table 1. Improved net return with increasing pregnancy rates1
|21-d pregnancy rate||Repro cost2||Increase in net return3|
1Cabrera - http://dairymgt.uwex.edu/markov/reader.php Net return increase compared to a 15% pregnancy rate and a reproductive cost of $20 per open cow.
2Reproductive cost per month for each open cow.
3Increase in net return per cow compared to a 15% pregnancy rate.