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October 2011 Archive for Dairy Today Healthline

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Dairy Today Healthline

Three Simple Rules to Monitor and Evaluate Reproductive Success

Oct 24, 2011

Three simple, yet robust, reproductive goals can tell you a great deal about reproductive success, regardless of herd size. If these goals are met, the herd is on track.

 
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By Dr. Andy Skidmore, D.V.M., Ph.D., Merck Animal Health
 
Inconsistent and confusing metrics for evaluation often leave dairy producers wondering how to interpret and apply reproductive data to their herds. Relevant information can be buried by inherent issues with data such as variability, lag time between conception and pregnancy diagnosis, bias of including pregnant or open cows only and momentum, a term used when historical data overshadow current data.
 
Reproductive management can be a very complex issue, but its direct effect on the bottom line makes it an issue that cannot be ignored.
 
Three simple, yet robust, reproductive goals can tell you a great deal about reproductive success, regardless of herd size. If these goals are met, the herd is on track. To assess progress towards these goals, just monitor three simple rules: 7.5, 80:80 and 80:150. They will help determine your areas of focus each month. 
 
Repro Rules


The 7.5 rule: 7.5% of the herd should become pregnant each month. This parameter is derived by dividing the herd size (both lactating and dry cows) by the calving interval expressed in months or weeks.

 

The 80:80 rule: 80% of all cows should be bred for the first time by 80 days in milk. First-insemination efficiency is another way of expressing the same idea, simply the percentage of cows bred for the first time between the voluntary wait period plus 21 days.

 

The 80:150 rule: 80% of the herd should be pregnant before 150 days in milk. Monitor cows that conceived 30 to 60 days ago and calculate the percentage that conceived before 150 days in milk.

The 7.5 rule
 
The first and most important parameter to monitor is that 7.5% of the herd becomes pregnant each month. Achieving that goal alone will keep your dairy in business. This parameter is derived by dividing the herd size (both lactating and dry cows) by the calving interval expressed in months or weeks. This measurement assumes that pregnant cows are not culled, the cull rate matches the replacement pregnancy rate and that the abortion rate is 5% or less. It can be monitored on a monthly or weekly basis, depending on herd size.
 
The 80:80 rule
 
The 80:80 rule simply suggests that 80% of all cows should be bred for the first time by 80 days in milk. Timed-synchronization protocols can make this number easier to achieve, reaching 100% in many cases. How the metric is achieved is not important, only that it is achieved. The simple logic that cows do not get pregnant unless they are bred is often forgotten. First-insemination efficiency is another way of expressing the same idea, simply the percentage of cows bred for the first time between the voluntary wait period plus 21 days. The allowable breeding space is greatly enlarged when this goal is met.
 
The 80:150 rule
 
Finally, the 80:150 rule indicates that 80% of the herd should be pregnant before 150 days in milk. Monitoring the rolling percent of the herd that is pregnant by 150 days in milk is often criticized because it suffers from inherent data issues, such as historic data overwhelming current changes. To compensate for these issues, monitor cows that conceived 30 to 60 days ago and calculate the percentage that conceived before 150 days in milk. This is the most current information available because of the lag time between conception and pregnancy diagnosis. Cows that are not pregnant before 150 days in milk should be evaluated to determine an action plan during the next four weeks. Cows with more than three services also should be evaluated in order to implement an action plan.
 
Reproductive management does not need to be complicated. If your reproductive goals are not being accomplished, investigate why. Benchmarking herd progress with these three simple rules provides consistency and identifies areas for improvement. When a herd follows the 7.5, 80:80 and 80:150 rules without abnormally high cull rates for reproduction, other parameters for success take care of themselves.
 
Dr. Andy Skidmore is a dairy technical services manager for Merck Animal Health. He lives in upstate New York and can be contacted at 716-474-2715 or andrew.skidmore@merck.com. 
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