1999 DHIA Herd Summary by Production
Dr. Allen Young
USU Extension Dairy Specialist
For the last several years, I have been putting together management reports for Rocky Mountain DHIA's Annual Summary. In addition to summaries based on herd size, there are reports summarized by herd production. Herd production level has been suggested as a factor that is correlated with many DHIA production parameters. In this article I am including a small selection of the total production parameters which were looked at because I think it can be instructive.
The selection criteria used to decide which herds were included in the reports are given below. These criteria excluded about 50 - 60 herds from consideration in the averages.
* Days on test had to be at least 365;
* Services per conception were equal to or greater than 1.25;
* Herd breed limited to either Holstein or Jersey,
* Number of cows in the herd had to be greater than or equal to 15;
* State code equal 87 (Utah); a spot check of averages for the whole affiliate shows values nearly identical to the Utah averages.
The number of herds in each production category resembles a bell-shaped curve with the greatest number in the 19-23,000 pounds of milk range. Herd size and production are directly related with the exception of two production categories (Fig. 1). It is interesting to note the large jump in cows per herd in the largest production category, 27,000 + pounds milk. Those 9 herds account for 20% of the total production for the data set.
The average % Low Somatic Cell Count (SCC) (0 - 4 linear score) is the percentage of your herd that has a linear score of under 4.5, or 283,000 SCC. The thing to keep in mind is that you want the average % Low SCC number to be higher if you want to have better herd udder health (i.e. less mastitis). My "rule-of-thumb" is 90% or greater in the average % low SCC category signifies a herd with excellent udder health. As herd production for Holstein herds increased the percentage of cows with a low linear score increased until around 22,000 lb milk and then leveled off (Table 1). This suggests that increased production is beneficial to udder health up to a point, then other factors seem to limit improvement in this area. The % low linear score for Jersey herds increased in a linear relationship suggesting increased production was beneficial to udder health (Table 2). Percent of cows with low SCC has stayed about the same over the last 10 years at 80%. This number should be better.
For several years we have been suggesting that heifers should calve for the first time at around 24 months of age. In the past 10 years, average age at calving has decreased from 27.6 months to a little over 26 months. This is moving in the right direction, but we haven�t made very much headway! As shown in Tables 1 and 2, only Holstein herds of 27,000 + pounds of milk and Jersey herds over 16,000 + pounds of milk had an average Age at First Calving below 25 months, suggesting that highest producing herds (and incidentally larger herds) do a better job of heifer raising. This is an area of missed opportunities.
Finally, a comment about Services per Conception (SPC). For Holstein herds, as production increased, SPC also increased (Table 1). However, days open was not different for the different production levels suggesting that these herds are doing better in some other aspect of reproduction to compensate for the poorer SPC. Interestingly, Jersey herds showed exactly the opposite trend, as production increased SPC decreased (Table 2). This is a very desirable combination.
These are only a few of several parameters that I looked at. For further information and to get the 1998 reports, you can look on the USU Dairy Extension Web site at:
Click on USU Dairy Research and Continuing Education, then DHIA Management Reports.
The 1999 reports will be added in the near future. If there is a relationship that you would like me to compute, drop me a line. I would love to hear from you.
Figure 1. Cows per Herd by Production Categories for Holstein herds (see Table 1).
Table 1. Selected Management Parameters, by Herd Production, for Utah Holstein Herds
|Avg. % Low SCC (0-4 LS)
||Age at First Calving
|14,999 & Less
Table 2. Selected Management Parameters, by Herd Production, for Utah Jersey Herds.
|Avg. % Low SCC
|Age at First Calving
|13,999 & Less