Fertility in Dairy Cows-The Bigger Picture

During this series of articles I shall be exploring the most important driver of herd productivity; herd fertility.

Over the coming months I shall look more closely at the reasons for reduced fertility in our dairy herds, ways to improve fertility in dairy cows effectively and ways in which farms can improve profitability through proactive fertility management.

So what have been the main reasons for declining herd fertility? A lot of these aspects are well documented but hopefully I can introduce some new ideas to consider with the objective of improving fertility productivity and profit.

In the last 20 years calving interval has increased by 24 days from 386 to 410 days, although this is historical data it is a good indicator to the problems modern dairy herds are now facing. Contained within this average figure will be the seasonal calving herds achieving the target 365 day interval and herds on reproductive management programs also returning good fertility figures.

It is therefore highly likely that there are a significant number of herds in the UK today losing a significant sum of money due to poor fertility. Driving this is the fact that there has been a reduction in first service conception rate from 55% to 40% (DairyCo, 2007) and a clear reduction in heat detection rates shown by Figure 1. Taken together both these measure produce a pregnancy rate that we are now all familiar with as one of the best measures of reproductive performance. Pregnancy risk which is % conception rate X % heat detection rate is reported to have a value of £24 per percentage pregnancy risk.

Disease & fertility
Figure 1- Reducing Heat Detection Rates (Cook, 2007)

Poor reproductive performance has a direct effect on profitability.

Blowey (2005) states that every day a cow is left empty costs a business £3.09. Over the 24 day period that the calving interval has been extended amounts to £74.16; this equates to £7,416 per 100 cows. With improved reproductive performance this cost is avoidable. 22% pregnancy rate will give a 386 calving interval

The obvious place to start is with the cow itself, as we are all well aware Holstein’s have been bred to produce more and more milk. These high yielding animals have a high demand for Dry Matter Intake (DMI) required for maintenance and milk, however post calving these levels of intake are especially hard to achieve resulting in Negative Energy balance (NEB) (Veerkamp et.al. 2003).

This increases the time to a cow’s first ovulation and lowers the levels of progesterone production making it more difficult for a cow to maintain her pregnancy (Butler, 2003). Transition cow problems, poor dry matter intakes (DMI) and negative energy balance (NEB) can lead to fertility issues. Milk protein production is a very good indicator of the adequacy of energy intakes post calving. Cows producing in excess of 1.1kg of protein are considered to have an adequate energy supply. (Gong, 2002). Monitoring protein production in fresh cows is an important indicator of transition and early lactation performance. Poor transition and fresh cow management can lead to increased incidences of disease which has a negative effect on fertility. (Figure 2).

Effect of SKC on disease incidence rate.
Figure 2 – effect of transitional health on days from calving to pregnancy.

If we look more in depth we can see how poor health in early lactation impacts reproductive efficiency (Figure 3).  Poor fertility in the fresh cow is in most cases the downstream effect of problems upstream. Transition management plays an important role in reproductive performance.

SKC indepth
Figure 3

Transition and fresh cow management significantly influences conception rate, however we must also consider the importance of heat detection rate as this is an essential part of pregnancy risk equation. Technology is becoming an important tool in heat detection.

Increasing numbers of farmers now have a heat detection system in place, whether this be computer based or a walk and chalk strategy. Both are effective ways of improving fertility and the results show this with increases in pregnancy rates.

According to Professor Crowe of Dublin University 75-85% of cows will ovulate by day 42 of lactation. Unfortunately a large proportion of these will not be seen on heat and be identified as being non-cycling and requiring intervention unless an effective method of heat detection is employed.

The recommended strategy is to conduct effective pre breeding heat detection and intervening with cows not seen bulling by 42 days. With good heat detection and fresh cow monitoring the need for the vet to routinely palpate each cow post calving is greatly reduced as is a number of cows requiring reproductive intervention.

Heat detection rates can be significantly improved by increasing the frequency of observations. However in most herds the time for heat detection is at a premium. Employing a combination of methods such as tail chalking, the use of activity monitors, and manual observations will pay dividends.

Where technology has been employed to replace manual heat detection through observation, heat detection rates often fall. This emphasises the importance of employing a combination of methods. The additional benefits of using manual heat detection are often overlooked as it provides an invaluable opportunity to assess other aspects of herd health for example body condition, lameness, cow comfort and hygiene which all have an effect on fertility. Consequently technology and cow management should be used together in order to maximise number of cows served whilst also maintaining cow health through good legs and feet, good body condition, reduced heat stress etc.

Transitional and fresh cow health are the key elements of cow management which influence reproductive performance. Success in both these areas results in optimal conception and heat detection rate which can be summarised through pregnancy rate.

I leave you with these questions to think about for the month ahead: are any of the issues discussed above issues on your farm? What steps are you going to take in order to overcome these problems? My hope is that the articles in the months to come will help provide you with answers to these questions in order to improve fertility management on farm.

For more information on fertility audits please speak to a member of the Dairy Technical Services Team.

Written by Will  Astley – Dairy Technical Specialist


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