Tracking your Herd’s Reproductive Performance

How is your estrus detection?

How is your conception rate doing?

Are you making enough cows pregnant?

How many cows are you servicing?

These are the questions that need to be asked and the areas need to be monitored to know how things are going reproductively and how they will go in the future. Alta has developed a relatively simple charting system that allows you to answer these questions, communicate with your staff and advisors and measure your reproductive progress over time.

Palpated Pregnancy Rate (PPR) is a measure of estrus detection efficiency that is calculated by dividing the number cows found pregnant at veterinary examination by the number of cows that were examined for pregnancy on that date. Twenty examined and 10 found pregnant would yield a PPR of 50%. 10/20=50%. By calculating and charting this measure at every vet check, you will establish the baseline PPR or estrus detection efficiency for the dairy. Estrus detection is a function of the people or system used to detect estrus activity and also a function of the cows’ ability to express estrus that can be observed. Estrus detection has two parts; people and cows. Once we know the baseline level of the PPR or estrus detection efficiency and there is a subsequent deviation, we have an early indication that something has changed, people or cows. We can then ask the appropriate questions to either correct a problem or reinforce a positive change.

I believe that if we create pregnancies at the rate of 10% of the adult milking herd each month on average, we will certainly meet all of our short and long term reproductive goals. Many larger dairies do vet checks at weekly or biweekly intervals. This makes the weekly target 2.3% of the cows milking and the biweekly target 4.6%. By knowing the conception rate (CR) of the herd we are then in a position to know how many cows must be serviced per period to create the number of pregnancies desired. For example; we are milking 1000 cows, doing vet check weekly and the herd CR is running about 33%.

Pregnancy examinations are done on animals that have been bred 35 to 42 days. Target pregnancies = 1000 x 2.3% = 23 per week.

Target services = 23 / 0.33 = 69 per week

The poster featured with the two charts, “Palpated Pregnancy Rate” and “Cows Serviced and Pregnancies Created” allows tracking of the four most critical areas relative to reproductive success; estrus detection efficiency, number of cows serviced, number of pregnancies created and conception rate trend. Conception rate trend is derived from watching the separation between the number serviced per week and the number pregnant per week. If the pregnancies are falling below the services, conception rates are declining for that period. Conversely, if pregnancies are rising above the serviced number, conception rates are improved in that period.

Perhaps the strongest part of this process is the communication aspect of the information graphed. There will be an immediate appreciation of strong and weak performance by all concerned; breeders, herdspersons, owners, veterinarians, nutritionists and other trusted advisors.

Article by Dr. Chet Rawson,
Alta Field Fertility Specialist

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