In my previous article about reproductive data and decision-making, I wrote about going back to basics and challenging your farm’s norms. I encouraged readers to find the Band-Aid solutions on their farms and prioritize what should be exposed and fixed.
Charlton nancy
Senior Advisor – Project Management / DeLaval

In this article, I will discuss stressors that can affect the reproductive health of your herd and how tools like sensors and a cow health index can enhance fertility.

When reviewing the pregnancy rate with the appropriate culling rate for your farm, I would suggest listening to a Jefo Nutrition podcast with Dr. Matt Lucy, where he discusses his research on how cows handle stress differently. Figure 1 from his research links possible stressors to the outcome of embryonic development and pregnancy.

Diagram depicting stresses that affect cattle

Research supports and experience knows that stressors impact pregnancy outcomes. Some act directly, such as heat stress, which impacts the ovarian function. Another stressor, such as metabolic disease (ketosis), causes the immune system to function poorly, leading to uterine disease and infertility. Lucy explores how cows handle the stressors leading to a difference in strain. Some of these stressors can be handled by some cattle and at some level. As the stressor is more severe and lasts longer, it will most likely affect more cattle. Some stressors at a lower level can influence cows more significantly. It’s important to discuss with your genetics adviser if you are selecting bulls that will sire daughters with the resilience needed in your herd.

Many of these stressors have an indirect impact seen only through a reduction in body condition score (BCS). It is this reduction in BCS, especially in the first 30 days in milk (DIM), which reduces pregnancies per artificial insemination (A.I.). This can be failure to conceive or loss of the embryo.


A suggested reason for the decreased fertility in cows in the first 30 DIM is that it creates a more long-term effect on circulating concentrations of progesterone. This research indicates that the longer the negative energy balance during the first 100 DIM, the greater the chances of having lower progesterone during the second and third estrous cycles. Anecdotal experience over the years would see farmers recording great physical heats before the voluntary waiting period followed by silence. The first-service conception rate was poor. When working with online progesterone sampling technology, this can be seen on the farmer’s computer with progesterone curves. Problem farms have many poor curves, which can be problem cows that have poor curves from the start, or the cows can start off with one or two normal cycles and develop low progesterone curves.

Lucy talks about many farms dealing with breeding problems cows. The reproduction team at the farm sets these cows up for a synchronization program, but the farm may also ask their veterinarian for advice, especially if the cows are not showing any heat signs. For organic herds, the cows have more time to recuperate in hopes they will start cycling.

Because we know stressors negatively impact fertility and BCS when there has been a health incident or a drop in dry matter intake (DMI), I advise the farms I work with to apply appropriate management strategies early to reduce stressors. For example, never overstock the transition cow area, or if heat or humidity lead to health issues or reduced DMI, then put in heat abatement with improved ventilation and cow cooling. While a health incident can lead to a reduction in pregnancy per A.I., not all cows respond the same way. All herds will have cows with health incidents, but to find the ones that need our help so it is possible to respond sooner is important for animal welfare. How to use the information to make management changes is also key to the herd’s longevity.

As farms grow and technology becomes more available, having a tool on the farm that provides a ready-to-use report to find sick cows will become mainstream. This index lists the cows that are in need of attention by utilizing the data from sensors, like milk meters, activity tags and BCS cameras, and amalgamating that information into an algorithm. These algorithms are usually created by the software provider supporting all the sensors. As Lucy states, the strain is different for each cow. A cow health index takes in sensor data plus expected yields and expected activity. The sensor alerts what has changed, and the expected yield and activity indicate the strain. Cows under more stress go to the top of the list and are red. Those with less strain are orange and yellow and score lower. The settings can adjust the number of animals presented to the farm.

BCS loss continues to be a significant factor in reduced pregnancies per A.I. – and yet, finding time to score cows and do it in a way where the data can be turned into information is a challenge. When using an automated BCS camera, data is collected every time the cow leaves the robot or the parlor. The trends in the first two to four weeks can be easily monitored. Losses throughout the lactation can be monitored, but it is the first 30 days that are most crucial to fertility.

The loss in the first 30 days already sets them up for a challenge. Monitoring by the farm manager and the feed adviser can be a tool to act on the transition cow program sooner versus two to four months down the road when cows are not cycling. An example for the management team is to utilize the BCS report to help in their decision to purchase more tools for heat abatement at the beginning of heat-stress weather or to develop a stricter protocol for stocking density in the transition cow period. If we know body condition loss in the first 30 days plays a key role in the fertility of our dairy herd, and the fertility of the dairy herd is a fundamental basis for dairy profitability, more should be done in a proactive way with this sensor’s findings.

There are stressors on all dairy farms, but it is the strain on an individual cow basis that will result in health, production and reproduction losses. What tools are you using to alert you to stressors and, most importantly, alert your management team to discuss and implement changes? These changes are needed to reduce the impact and strengthen the systems on your farm so your health, production and reproductive goals lead to a profitable and sustainable enterprise.  end mark

References omitted but are available upon request. Click here to email an editor.

  • Nancy Charlton

  • Veterinarian
  • Senior Adviser and Project Management
  • DeLaval