December 13, 2021 at 10:04 p.m.

Painting by numbers

By Jim Bennett- | Comments: 0 | Leave a comment

Numbers can tell a story. For example, numbers that represent key performance indicators can tell at least part of the story of a dairy farm. When numbers from a group of farms are combined, they can tell the story of the group.
Every year, our practice completes a benchmarking project to paint the story of a large share of the freestall herds in the practice. Let’s take a look at some of the numbers to paint a picture of these dairies for the time period from mid-2020 to mid-2021. The numbers below are the average (mean) of 29 herds representing over 21,000 cows. The numbers for each herd represent a 12-month average for each parameter.
First, inventories and culling: The ratio of youngstock to cows was 89% this year. This is total heifer inventory divided by lactating and dry cow herd size. The trend here is downward. Farms used to typically have well over 100% heifers to cows. The turnover rate (culling and dead divided by total number of calvings) supported by the heifer supply (live births minus deaths and sold) in the last 12 months was 36%. The actual turnover rate for the herds was 30%, so on average, herds are producing enough heifers to maintain turnover rates. The average culling rate (sold and deaths divided by average lactating and dry cow herd size) was 34%. The average percentage died was 4%, and the percentage of herd culled in the first 60 days of lactation was 8%.
The average age of the herd was 47 months, and the percentage of herd that are in lactation one was 35%. We have seen a trend of reducing culling and increasing average herd age in the last few years, but the trends had been going the other way until recently. In 2004, the average culling rate was 32%, but by 2013, it had reached 40%. The average age was 46 months in 2004 but reached a nadir of 43.5 months in 2014. Heifer supplies have been getting smaller, and we expect the effects of smaller inventories on culling and herd age to become more prominent in the next few years. Farms will need to learn how to manage lower culling rates.
Production: Our herds averaged 94 pounds of energy-corrected milk (ECM), with remarkable component levels of 4.1% butterfat and 3.2% protein. The average pounds of fat and protein combined per cow per year was 6.4. This is a testimony to our farmers’ management skills and the efforts of their nutrition professionals. For energy corrected milk by lactation, we see averages of 82, 97 and 101 pounds for lactations one, two, three and up, respectively. On average, lactation three and up cows gave 19 pounds more ECM than lactation one, which is why our farmers want a greater percentage of older cows in their herds.  
Reproduction: The average for pregnancy rates and conception rates was 32% and 49%, respectively. In 2004, the respective averages were 18% and 34%. Our farmers have had remarkable success increasing pregnancy and conception rates in the last two decades. The success in improving conception rates is particularly stunning, because it is often difficult to significantly increase conception rates in dairy herds. Improvements are most likely due to more farms using timed A.I. programs, improvement in timed A.I. programs and better herd nutritional management.
Youngstock pregnancy rate and conception rate averages were 28% and 57%, respectively, with a wide range of pregnancy rate (4%-44%). The value of high youngstock pregnancy rates is becoming better understood by our producers, as lower youngstock pregnancy rates are usually due to low service rates rather than conception rates, and thus are fairly easy to change.
Abortion rates (total abortions divided by average herd size) averaged 8% for cows and 2% for youngstock. Abortion rates in cows tend to track conception rates; as conception rates have gone up, abortion rates have declined. Twinning rates have also declined to an average of 3% last year. Most likely this is due to more herds using timed A.I. programs, and better nutrition and control of periparturient diseases.
Youngstock: 5% of heifers died up to calving; this includes 3% of heifers that died in the first 60 days of life. The average age at first calving was 23 months. This has declined significantly over the last two decades. The average net herd replacement cost was $1.46 per hundredweight ECM.
Disease rates: The ability to capture disease rates is limited to diseases where one can develop a relatively standard definition and by the ability of the producers to record that data. For the farms that have good data, the average rates of displaced abomasum, retained placenta, milk fever, ketosis and metritis were: 1.5%, 3.1%, 2.2%, 9% and 5%, respectively. These rates are calculated by the number of cases divided by total number of calvings, because they occur after calving. All of these have declined tremendously over the last couple of decades. For example, the highest rates of displaced abomasum, metritis and retained placenta reported for any year since 2004 were 7%, 18% and 8%, respectively. Clearly, fresh cow health is much better than it used to be.  
This is a snapshot of some of the more interesting parameters tracked in our last herd survey. So, now you have a partial picture of how dairies look in southeastern Minnesota. How does the picture of your dairy compare?
    Bennett is one of four dairy veterinarians at Northern Valley Dairy Production Medicine Center in Plainview, Minnesota. He also consults on dairy farms in other states. He and his wife, Pam, have four children. Jim can be reached at [email protected] with comments or questions.


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