I Can't Get My Cows Pregnant: Where Do I Start?

"I'm working harder than I ever have and am having more difficulty getting my cows pregnant." This quote from a Central Minnesota dairy producer reflects the thoughts of dairy producers throughout the country. It has been well documented that reproductive efficiency is on the greatest decline since the mid 1980s with services per conception and days open increasing. Most other countries have seen the same trend.

So, why the decline? There are several factors that influence whether a cow becomes pregnant. These include: milk production, age of cow, breed, heat stress, estrus detection efficiency, insemination technique, early embryonic death, metabolic and infectious diseases and many more. Some blame the increasing milk production per cow levels as the single factor for the decline. Summaries of the research do show there is an antagonistic relationship between milk production and reproduction, but this relationship is relatively small compared to other factors. In fact, typically higher producing herds have better reproductive performance that low producing herds.

Because of the many factors affecting a farm's reproductive performance, it can be difficult to develop an action plan to improve reproductive performance. Dr. Phil Senger, Washington State University, proposes a system that organizes factors affecting fertility into three categories:

1) Controlled by man;
2) Controlled by the reproductive system of the cow;
3) Natural to any herd or cow (Table 1 ).

By focusing on changing the factors that can be influenced by the herd management (categories 1 and 2), you are more likely to improve reproductive performance.

Table 1. Factors affecting fertility of cows

CONTROLLED BY MAN	CONTROLLED BY THE COW	NATURAL TO ANY COW
High Management Influence	Moderate Management Influence	Low Management Influence
Heat detection efficiency	Dystocia	Breed
Heat detection errors	Retained placenta	Age
Inseminator skill	Uterine infection	Production
Fertility of the bull	Cystic ovaries
Semen storage and handling	Embryonic death
Heat stress	Twinning
Lameness and footing
Vaccinations
Transition cow management

Let's look at some of the "Controlled by man" factors that can have the greatest control over improving dairy herd reproductive efficiency.

1. Heat detection efficiency - For most herds, improving heat detection efficiency has the most potential to achieve more pregnancies in a timely manner. Research shows that less than 50% of heats are detected in most herds. In our confinement housing systems, cows are in heat less hours with fewer mounts during the estrus period. It's not surprising that many heats are missed with visual heat detection only because most cows are being mounted from 2-6 minutes during the entire heat period. Options to improve heat detection efficiency include increased focus and time spent detecting heats and/or use of heat detection aids. Another great option is to implement a timed insemination program. The key to the success of these programs is compliance. A system must be developed to ensure that the right cows get the right shots at the right time.

2. Heat detection errors - Up to 30% of cows inseminated on some herds are not in estrus. This is caused by a combination of identifying the wrong cow and too much reliance on secondary signs of heat. Employees should be well trained in heat detection and a system should be developed to minimize heat detection errors.

3. Inseminator skill - This factor is often overlooked when troubleshooting herd reproductive problems. Research indicates there is a 15-20% difference in conception rates among inseminators. Most management teams assume that the person inseminating the cow has been properly trained and has the skill to inseminate accurately. Records should be used to monitor performance. Annually have your semen supplier conduct a refresher course on proper semen handling and placement. Develop a protocol to keep all AI equipment clean and check temperature of the thaw bath on a regular basis.

4. Heat stress - Reproductive performance is extremely sensitive to heat stress. Heat affects conception rate, heat expression and early embryonic death. Every farm needs a plan to manage heat stress. There is research available on the best way to minimize heat stress with different systems.

5. Vaccinations - Many of the viral and bacterial diseases can decrease reproductive performance. Work with your veterinarian to develop a vaccination program that works best for you. The best designed vaccination program will not be effective if it is not implemented correctly. Make sure vaccines are handled correctly and accurate records are kept so cows are given the correct vaccinations at the correct time.

6. Transition cow management - Much of an individual cow's likelihood of reproductive success is determined at the time of calving. A sound nutrition and management program is essential. All cows, including dry and recently fresh cows, must be kept clean, dry and comfortable. Some of the factors controlled by the cow (retained placenta, uterine infection and cystic ovaries) are influenced by management of cows around calving. Work with your management team to develop a transition management plan to minimize diseases and allow cows to increase dry matter intake rapidly after calving.

Several farms have been able to maintain good reproductive performance while achieving high production. They have accomplished this by focusing on those factors they can influence on their farm. By spending your time and energy on the reproductive management factors within your control, you too can achieve acceptable reproductive efficiency in your herd.

By Jim Salfer, Regional Extension Educator-Dairy
Dairy Connection Articles - University of Minnesota Extension