DHIA Characteristics Based on Herd Size

Dr. Allen Young
USU Extension Dairy Specialist

Each year I do some summary reports based on DHIA values for the previous year. I categorize dairies based on either rolling herd average milk or herd size. For this article I want to use some of these reports and concentrate on some DHIA characteristics based on herd size, especially large herds. The data set is for 2002 and 2003 and includes herds from Utah, Montana, Nevada, Wyoming and parts of southeastern Idaho. As a disclaimer, I am not trying to pit large against small herds. I try to be size neutral and let the numbers tell the story. I am providing this information because herd size seems to be an issue.

The impact of large herds on the industry can be seen in Table 1. This table is only for herds whose predominant breed is listed as Holstein. Data were summarized for herds with Jersey cows; however, there were only 15 herds listed, which made the sample size too small for comparisons. Comparing the largest herd size category against the others demonstrates what others are also seeing, which is that even though this size group makes up only 11% of all herds, it includes almost 43% of all cows and almost 45% of the total milk produced. The largest herds produce nearly as much milk as all others combined and have more cows than the smallest three categories combined.

Table 1. Characteristics of Holstein herds in the RMDHIA affiliate for FY2003.

Category # Herds Cows/Herd RHA Milk % Herds % Cows % Milk
< 75 39 57 18,960 19.4 4.1 2.4
75-150 69 115 21,116 34.3 14.7 13.5
150-300 48 233 22,784 23.9 20.7 20.5
300-500 23 411 23,799 11.4 17.5 18.1
500+ 22 1053 23,942 10.9 42.9 44.6
Total/Avg. 201 269 21,712 100 100 100

Comparisons with averages from the previous year (2002) found in Table 2 demonstrate that average herd size is increasing, with the large herds adding an average of almost 200 cows per herd in 2003 compared to 2002. Interestingly, average milk per cow for the largest herd size group did not change between the two years. Because of the larger average herd size, this group also increased its portion of all cows and milk by 5.1% and 5.3%, respectively. As an aside, the number of herds decreased from 2002 to 2003 by 21 herds, yet the total number of cows tested increased by almost 1500. Surprising to me was the fact that the smallest herd category had the same % of total herds for the two-year period, yet their contribution on the total number of cows and amount of milk is eroding.

Table 2. Characteristics of Holstein herds in the RMDHIA affiliate for FY2002.

Category # Herds Cows/Herd RHA Milk % Herds % Cows % Milk
< 75 43 56 19,551 19.4 4.6 3.9
75-150 79 113 21,407 35.6 17.0 15.8
150-300 53 224 22,601 23.9 22.6 22.3
300-500 24 394 23,985 10.8 18.0 18.6
500+ 23 862 23,964 10.4 37.8 39.3
Total/Avg. 222 237 21,876 100 100 100

In addition to the obvious differences listed above, the following comparisons between the largest size group and all other herds were noted. Herds in the largest size category:

Were higher in:
- Services per conception
- % heat detection

Were lower in:
- Days in milk at first service
- Average age at first calving

Were roughly equal in:
- Days open
- % of herd with low SCC
- Days dry
- Days in milk
- % heats resulting in a calf

Peak milk and Service Sire PTM roughly paralleled the changes in average RHA milk production for each group.

The high heat detection rate of the largest herd size group was offset by the high services per conception that resulted in roughly equal days open compared with the other groups. It is remarkable how similar the largest herd size category is with the other groups with the exception of age at first calving, which is 24.6 months (1.3 months less than the next category (300-500 cows group).

So, what can we conclude from all of this? In the absence of financial records, we can only speculate based on what the DHIA records suggest. It appears that large herds are getting larger and are grabbing a bigger piece of the pie of total milk produced. I think this will have extremely profound marketing implications for the future. I already see some of these dairies marketing milk on their own terms and wonder how this will affect the industry as a whole. The numbers also suggest that in many ways, large dairies are more similar than otherwise to smaller herds in DHIA production values. They have many of the same problems, but on a bigger scale. The one area in which they clearly do a better job is heifer raising. One could speculate that this is because they �farm� out their heifer raising to a professional raiser or they have the facilities and labor to do a better job of raising their own heifers - a group that is often forgotten on many dairies. This is an important area that needs to be improved on other dairies.

Finally, are small dairies a thing of the past? I don�t know, and if I did, I certainly won�t say it out loud; however, if you look at the change in number of dairies between 2002 and 2003, then the categories of <75, 75-150, and 150-300 cows lost 19 of the 21 herds (4, 10, and 5 dairies, respectively). If you compare 2002 vs. 2003 based on the difference in percentage between the two years, the 75-150 cows category lost 1.3% and the two categories of 300 or more cows picked up the same amount. I sometimes wonder if herds in the 75-150 cow group may be vulnerable because they are almost too big for one person to manage, yet may not be big enough to hire the labor needed to handle their needs.

More work needs to be done with determining whether large dairies are more efficient than smaller ones and how to evaluate these differences. If you have comments, feel free to contact me at (435) 797-3763 or alleny@ext.usu.edu. ©