Reproductive nightmares. They can occur on any dairy at any time. Even in herds which score an "A" in almost every aspect of the operation, one problem can bring reproductive performance tumbling down.
Take, for example, one 225-cow dairy. Days to first breeding had topped 100, and the percentage of cows not bred after three services had hit 20 percent. That was the case when Fort Collins, Colo., veterinarian Arden Nelson started to investigate. Nutrition was good, the cows were comfortable with clean, well-bedded stalls; in fact, everything on the equipment and facilities side was excellent. The problem had to be elsewhere.
Employees reported the cows weren't showing heats. Examination of the heat detection rate confirmed that – of all cows eligible to be bred, only 40 percent of heats were being detected. However, the problem wasn't the cows, but rather the heat detection program.
About the time the problem was discovered, a son returned home from college. A good "cow man," he started spending 20 to 30 minutes three times a day watching for heats. Almost immediately, the heat detection rate started climbing and the days to first service started dropping.
Often times, the most frustrating part of finding the cause of a reproductive problem is knowing where to look, says Nelson. That's where production records analysis comes in. To help you get started, here's five critical reproduction records you can use to help pinpoint problems and improve the reproductive management of your herd.
When it comes to heat detection, you really only have two choices – "do it well or don't do it at all," says Steven Stewart, dairy production medicine veterinarian at the University of Minnesota. When you use heat detection, you have to make a commitment to do it right. However, if you can't take time each day for heat detection, or your herd has a poor heat detection rate, then a targeted breeding program may be for you.
When evaluating heat detection in smaller herds, Stewart runs a DairyComp 305 report, called Q-sum for heat detection, using information from DHI records, or from the dairy's own computer system. After 50 days in milk, each cow is given an estimated date of when heat should occur. Using that information as a starting point, the report shows which heats were missed and which were detected.
In larger herds, Stewart runs another DairyComp 305 report, called retrospective 21-day heat trial. This report divides the previous year into 21-day intervals and estimates when each cow should have had a heat, and then counts actual heats and breedings to calculate a heat detection rate for each 21-day interval. These types of reports, says Stewart, can help spot trends quickly.
In addition, you can calculate a heat detection rate for your herd, says Ray Nebel, extension dairy scientist, Virginia Tech. Or, some DHI records systems will calculate it for you. Generally, heat detection improves after the first service because you know approximately when each cow should come back in heat.
You'll want to evaluate heat detection rate for first-service animals and for all other animals.Nebel uses these formulas:
Strive for a heat detection rate of 70 percent in each category. If your detection rate slips below 50 percent, in either category, start looking for the cause. Consider a refresher course on heat detection for employees and using heat detection aids to improve performance.
Days to first service
Average days to first service tells you how long it takes to detect first heats and service the cows. How quickly you're catching heats and breeding cows directly affects the length of the calving interval and the profitability of your herd, explains Nelson.
You can determine average days to first service from your monthly DHI report. With herd management software such as DairyComp 305, you can run a report which averages the days in milk at first breeding for groups of cows.
To determine what your ideal days to first service should be, Nebel recommends adding 11 days to your voluntary waiting period. So, for example, if you have a voluntary waiting period of 45 days, and you add 11 days, your average days to first service should be 56 days.
Most healthy cows resume cycling within 30 days after calving, says Nebel. The first cycle often produces dimin-ished signs of heat, but the second cycle should occur by days 48 to 52. Al-though 56 days is achievable, Nebel sets a goal of 75 days. However, whenever the average creeps above that, you need to look at these areas to find the cause:
1. Heat detection. Investigate to determine if your employees know how to observe heats, if they spend enough time looking for heats, and if they know how to read heat detection aids – chalk, mount detectors or whatever system you use – correctly. You may need to conduct a refresher course.
You also might consider starting a targeted breeding program. Targeted breeding groups heat activity and allows you to reduce the time spent detecting heats. Talk to your veterinarian to determine if such a program is right for you.
2. Body condition. If heat detection seems satisfactory, then look at the change in body condition scores of your newly-fresh cows. Nebel uses the guideline that cows should not drop more than one point in body condition after freshening. So, if your cows calve at a score of 3.5, then after freshening they should not drop below 2.5. Cows that drop more than one point often spend an extended period of time in a negative energy balance which delays their return to estrus and cycling. Check the pre-fresh, newly-fresh rations, and feeding management practices.
Conception rate measures how accurately you detect heats, place semen and the fertility of your cows. Your goal: pregnant cows.
The DHI Herd Summary report lists successful breedings by each month of the year, with a total for the past 12 months. The report also lists statistics for first, second and third services separately, as well as the success rate for total services. Or, if you'd like to calculate it from your records, simply divide the number of cows confirmed pregnant at the next pregnancy check by the number of cows serviced during that one breeding period, usually calculated by month.
When looking at conception rate, look at the conception rate at first service separately, and then look at conception rate for second and later services for the most recently palpated animals. With first-service animals, the conception rate tells you how well you're doing getting the cows bred successfully on the first try. (Nebel uses a goal of 55 percent.)
However, for all services except first, Nebel uses a goal of 50 percent for conception rate.
When either rate drops below 30 percent, you need to take action. Check the following in this order:
1. Review your AI program. Have employees been trained in proper insemination techniques? Is the semen thawed correctly and used promptly? Are cows handled calmly both before and after insemination? If you suspect problems in any of these areas, ask your AI cooperative to conduct a refresher course for all employees who breed animals.
2. Check breeding intervals. Looking at the records of when you bred cows can help you determine if heat detection is a problem. For example, if the interval between two subsequent breedings is less than 18 days, and prostaglandins were not used, then one of the reported heats was probably incorrect. If the interval between two subsequent heats is between 24 to 36 days, the cows could be experiencing early embryonic deaths. And, if the interval be-tween two subsequent breedings is 36 to 48 days, it signals a missed heat.
To correct a heat detection problem, review signs of heat with your employees or consider a targeted breeding program. If the breeding interval suggests early embryonic deaths, Nelson suggests looking for these possible causes: high milk urea nitrogen levels, mycotoxin in the feed or anything that would cause an elevated body temperature, such as heat stress, viral infections and toxic mastitis.
3. Test milk progesterone levels. Milk progesterone levels drop when cows experience estrus. Checking the progesterone levels of the cows you breed will tell you how accurately employees detect heats. To do this, collect a milk sample from each cow after breeding, or at the first milking after breeding. Freeze the samples until you get a about 20, and then have your veterinarian run a progesterone test. Any cows which test high (> 1 to 2 ng/ml), are not really in heat.
4. Examine milk urea nitrogen (MUN) levels. If your DHI offers MUN testing, consider adding that record to what you receive each month. High MUN levels have been linked to poor reproductive performance, and can be used as another tool to help pinpoint the cause of a problem. If MUN levels are 18 or higher, check the ration. Chances are, the ration has excess protein or is low in fermentable carbohydrates.
5. Review your vaccination program. If the cows fail to conceive or experience early embryonic deaths, it could be due to a lapse in design or implementation of your vaccination program. Review your vaccination records to make sure all animals have been getting their vaccinations as scheduled. And, contact your veterinarian to make sure your vaccination program provides complete coverage.
6. Evaluate cow health problems. When none of the five areas listed above reveal any clues to the cause of a low conception rate, it's time to start checking individual cows and cow records. Check calving difficulty, retained placentas, and metritis rates for animals in the breeding group. And, have your veterinarian palpate cows to check for problems, such as cystic ovaries.
When using days open, don't look at the average for the whole herd, says Meg Cattell, a veterinarian in Loveland, Colo. The average days open can give you a false impression of what's happening because it includes information from cows that are already pregnant, problem breeders, and cows that haven't passed the voluntary waiting period. Days open are best applied to groups of cows.
For example, Cattell looks at days open for those cows that still are open after 150 or more days in milk. Those animals represent potential reproductive failures. Your goal: less than 20 percent of the animals in the herd should be more than 150 days in milk and still open.
Another way to look at days open is by looking at the distribution of the herd. For a herd that calves year around, Nebel uses the following goals:
- 40 to 50 percent of the cows should be open less than 100 days.
- 30 to 40 percent should be open between 100 to 150 days.
- No more than 20 percent of the cows should be open more than 150 days. Whenever you see the group that is 150 days or greater increasing beyond 20 percent, check your heat detection program, conception rate, early embryonic deaths, and whether your pregnancy checks and records are up-to-date.
If your herd doesn't calve year around, or has just purchased 200 heifers and freshened them as part of an expansion, talk to your veterinarian about what goals are appropriate.
"Sometimes it's the after-the-fact financial measure-ments which motivate best," says Cattell. For example, you spend $1 to $2 per day to feed a cow for each day she's dry.
When a cow doesn't get bred back right away and her milk production declines, producers tend to dry her off and put her on the less-expensive dry cow ration. With these cows, average days dry can exceed the goal of 50 to 60 days dry pretty easily. And at $2 per day, the extra cost adds up quickly.
Keeping an eye on this record can help you keep cost under control and see the delayed, but direct economic repercussions of poor reproductive management. For example, if a 100-cow herd has an average days dry of 80, half the herd would have 100 days dry and the other half would have 60 days dry. The direct cost would be $4,000. (50 cows x 40 extra days dry x $2/day = $4,000.)
In addition to days dry, you also should track the number of cows culled for reproductive reasons. Your goal: reproductive culls should not exceed 15 percent of total culls. Remember, each cow culled, on average, is a $700 loss (replacement cost - salvage value).
Anytime that days dry starts to creep past 60, and reproductive culls climb above 15 percent, you need to start looking for answers. Check your heat detection program, conception rate and your record-keeping program.
Remember, one record alone can't tell you everything. But using these records in combination, and working with your veterinarian can help you improve your herd's reproductive efficiency.
For first-service animals:
Days in estrous cycle divided by [(Day to 1st service - VWP(1)) + 11] multiplied by 100
For all other animals:
(Services/pregnancy - 1) divided by [(Avg. days open - Days to 1st service) divided by 21] x 100
(1) VWP = voluntary waiting period