D A I R Y I n i t i a t i v e s N E W S L E T T E R
V o l u m e 8 I s s u e 1 S p r i n g 1 9 9 9

Reproductive Performance

by KENN BUELOW, STEVEN STEWART,
PAUL RAPNICKI, and SANDRA GODDEN
Dairy Production Medicine Veterinarians

If you'd like to boost your profitability, consider evaluating your herd's reproductive performance. Depending on where you are now, you can save $75 or more per cow by improving your herd's reproductive track record.

The first and simplest step to improving your reproductive program is to get in the habit of making a list every week of open cows that need to be bred. Then find those cows and/or bring them into heat, detect the heat, and get semen into them. We know of only one fluid that, when infused into a cow's uterus, is proven to increase the pregnancy rate: SEMEN.

After you have accomplished this, the next step is to gather information about your dairy's past and current reproductive performance and compare it to other dairies in your region. This will help you determine where you should focus your efforts. Finally, estimate the potential financial benefit of changes and, if they appear worthwhile, make them.

An example

Let's use an example to show how this works. In Table 1, we have summary data from a Minnesota herd generated using DHIA records and DC305/Scout. The report calculates three-week heat detection rates (HDR), pregnancy rates (PR), and conception rates (CR) for the past year.

To create this report, the program counted the number of cows eligible to be found in heat and bred in every 21-day estrus cycle (column 2) and the number actually found in heat and bred (column 3). The number of animals found in heat divided by the number expected in heat gave us the HDR (heat detection rate, column 4).

Next, the number eligible to become pregnant (column 5) was counted. This number is equal to or less than the number eligible for heat. It is less when a cow is bred but not determined open or pregnant to that breeding because of culling or long intervals between pregnancy exams. Also counted were the number of cows actually becoming pregnant (column 6). The program then divided column 6 by column 5 to determine PR (pregnancy rate, column 7). Finally, using the equation HDR x CR = PR, we inferred the CR for each three-week window (column 8).

We next used this information to answer questions about pregnancy rate. Is it low? If it is low, is it a seasonal, acute, or chronic problem? Is the low pregnancy rate a result of poor heat detection or poor conception? To decide, we compared this information with industry standards (Table 2). We concluded that the dairy had an acceptable conception rate except for mid to late June (6/9/98-6/30/98). However, the pregnancy rate was too low due to the poor heat detection program.

Next we assessed the financial impact of increasing the pregnancy rate. This depends on where a dairy's pregnancy rate is and how much improvement it makes. The lower a dairy's pregnancy rate, the greater the benefit of an increase. If pregnancy rate increases from 12% to 13%, the additional net income from increased milk production and reduced culling would be approximately $77/cow/year. Increasing the pregnancy rate from 18% to 19% would only increase net income approximately $23/cow/year. Increasing the pregnancy rate from 26% to 27% would only increase net income approximately $4/cow/year. Thus, if a dairy is able to maintain a pregnancy rate greater than 22%, time, money, and management efforts should be focused at a problem with a greater potential return.

In our example, the dairy made changes to its heat detection program in early September, resulting in a pregnancy rate of 13% to 19%. The number of open cows dropped from approximately 520 (midsummer) to 350. If we assume the pregnancy rate was 11% before the heat detection change and is now 16% (and will continue to be for the next year), we can expect an increase in net income of $301/cow/year.

Your farm

A table like the one we made for the sample farm can tell you many valuable things about your reproductive program.

It can show you the number of cows open and eligible to become pregnant for every 21-day period in the last year.
It can show how heat detection, conception rate, and pregnancy rate vary.
It can show progress. You can evaluate a management change to improve heat detection in three weeks -- that's rapid feedback. A management change to improve conception rate can be evaluated in eight weeks.
Finally, it can show you how many cows are open and need to be bred. If this number is dropping, a greater percent of the herd is pregnant.

Depending on your current circumstances, you may find this information to be a big boost as you work to improve your farm's profitability.

Table 1. Reproductive data from a Minnesota dairy.
Date	# eligible for heat	# detected in heat	% heat detection (HDR)	# eligible to be pregnant	# pregnant	% pregnant (PR)	Inferred coneption rate %(CR)
12/23/97	713	158	22	708	51	7	32
1/13/98	673	190	28	670	63	9	32
2/3/98	782	174	22	781	59	7	32
2/24/98	739	192	25	737	56	7	28
3/17/98	673	188	27	666	56	8	30
4/7/98	609	158	25	607	79	13	52
4/28/98	545	103	18	542	69	12	67
5/19/98	549	79	14	549	43	7	50
6/9/98	516	65	12	515	7	1	8
6/30/98	518	106	20	517	48	9	45
7/21/98	518	146	28	516	37	7	25
8/11/98	534	161	30	531	43	8	27
9/1/98	569	237	41	564	74	13	32
9/22/98	600	284	47	582	82	14	30
10/13/98	563	268	47	547	105	19	40
11/3/98	523	266	50	513	100	19	38
11/24/98	491	264	53
12/15/98	353	207	58
Averages			31			10	32

NOTE: This report can be generated with information from DHIA, but is only accurate if the dairy is recording -- and making sure DHI is entering -- all heats, breedings, and pregnancy/ open information.

Table 2. Average values from 2,561 Minnesota DHIA herds for 1998.
	Low range (bottom 5%)	Average	High range (top 5%)
Heat Detection Rate	17%	35%	49%
Conception Rate	20%	34%	48%
Pregnancy Rate	5%	12%	19%

Reproduction's Down -- What's Up?

Reproductive performance in Minnesota dairy herds began to drop about five years ago and has been down ever since. What's going on? University of Minnesota veterinarian Brad Seguin suspects the culprit is BST.

BST first became commercially available to Minnesota dairy farmers in February 1994. It allows cows to stay in milk longer, which can affect reproductive performance in two ways. First, increased production stresses cows nutritionally, so they have fewer resources to devote to getting pregnant. Second, being in milk longer means cows can stay profitable and so stay in the herd longer even though they're not pregnant, giving a larger window of time for breeding. In other words, BST may be making it tougher for a cow to get pregnant, but because overall productivity increases, that may not necessarily be a bad thing.

Tips for Improving Reproductive Performance

Be more willing to put semen into questionable heats.
Use aids -- Kamar heat detectors, tail chalking, pedometers, electronic patches.
Make heat detection a priority. Have one person responsible for it, and dedicate a consistent time for heat detection every day.
Allow cows access to good footing outside of feeding time to allow expression of heat.
Use prostaglandins and other hormones to help with timing of breedings for cows not found in heat after more than 80 or 90 days in milk.
Provide good cow comfort to keep cows' feet and legs healthy.

D A I R Y I n i t i a t i v e s N E W S L E T T E R
Volume 8 Issue 1 Spring 1999

Dairy Initiatives

Dairy

Department of Animal Science