Fertility in Dairy Cows – The Bigger Picture – Part 2

Transition Management-The silent killer

In the second article in this series I am going to explore the effect of transition management on the fertility of dairy cows. Last month I looked at all the aspects which had affected fertility in the last 20 years. One of these was clearly transition management and as it is possibly the dominant influencing factor, it is only right that we explore this first.

Over the past few years’ transition management has become a major talking point: managing cows correctly during the dry period leading to better

BCS Source Elanco
Figure 1 BCS 3 Cow, Source: Elanco

performance after calving and ultimately increasing profit margins. Genetically fertility has low heritability, management of the cow has more of a bearing on fertility than fertility index with a heritability of 3%. Therefore transition management becomes the obvious starting point when looking at fertility problems within the milking herd.

What are the main problems with transition management which cause fertility issues after calving?

 

To determine this, we need to look back at the point where the cow was dried off. It is no surprise that the health of the cow at drying off has an impact on the health of the cow at calving. At this point there are two major aspects which can be influential. The first of these is lameness – a lame cow during the dry period has a reduced appetite which is shown by a reduction in rumen fill (Hassall et.al. 1993: Singh et.al 1993).

Rumen fill is vital post calving as it is a good indication of whether the cow has transitioned smoothly into lactation. It is a key measurement entered into our new Wynnstay DTSmetrics analysis which also looks at Feeding space, stocking rate and grouping, which have been shown to be a crucial aspect of transition cow management.

A low rumen fill will result in a drop in body condition score which will impact on performance, fertility and health. As a result of this the lame cow will be pre disposed to suffering from metabolic issues at calving, with reduced intakes increasing the risk of ketosis and milk fever. The other aspect we need to consider at dry off is Body condition Score (BCS). A BCS between 2.5 and 3 is the desired score which is shown in figure 1.

Effect of Sub Clinical Ketosis on other problems effecting fertility
Figure 2: Effect of Sub Clinical Ketosis on other problems effecting fertility

The major concern here are the cows outside the desired window particularly cows above a BCS of 3, as these cows have laid down body fat, which is going to cause calving problems. So although transition management in itself has a large impact on fertility in the dairy herd, it is important to note that this all begins before we even get to the transition period when drying off takes place.

The question now is what are the problems which we see at the beginning of the fresh cow period which are caused by these two factors occurring at drying off? Firstly Ketosis is linked to both lameness and BCS, as both have a negative impact on intakes post calving. Ketosis is the single biggest contributor to fertility issues during the service period and pre disposes the cow to additional health problems as shown in figure 2.

Note from this table that sub clinical ketosis alone will increase Calving index by 22 days. Using the figure of £3.09 per day left empty (Blowey, 2005) this means a cost of £67.98 per cow, a significant cost to the business.  One influencing factor here is an increase in time to first service of 5 days (Heringstad et.al. 2009) and also a significantly higher loss of pregnancies after service caused by negative energy balance and a predisposition to greater incidence of uterine infections (Figure 2). These losses amount to 8.3% (Ribeiro et.al. 2013).

Milk Fever is an additional concern. There is an increasing awareness that this is caused by unsatisfactory transition diets affecting calcium mobilisation. In reality we should either be keeping calcium levels in the diet very low, using a calcium binder like Calfix or maintaining calcium intake and operating a partial or full DCAB system in order to promote calcium mobilisation. What impact does this have on fertility? Figure 3 shows the negative impact of milk fever. 

Milk fever reduces muscle function which leads to an increased risk of Retained Foetal Membranes leading to increased risk of metritis. This has the biggest impact on

Figure 3 consequences of milk fever (Source: www.xzelit.com)
Figure 3 consequences of milk fever (Source: www.xzelit.com)

fertility rates post calving, with 31% of dairy cows suffering from this losing pregnancies between day 30 and 65 after service (Ribeiro et.al. 2013). We also must consider the incidence of milk fever across the herd with every 1 cow suffering from clinical milk fever meaning that another 4 to 6 cows are suffering from sub clinical milk fever. This is why it is so vital we get transition management right as many of these diseases/infections are underlying, and we often don’t realise the impact that they are having. This is clearly shown by both Milk Fever and Ketosis.

We also need to consider metritis and the biggest influencing factor to this is immune suppression. This happens during the 2-3 weeks both pre and post calving. Typically a low level of immune suppression will have no visible effect, however the level can be increased through milk fever which then results in an increase in occurrence of metritis (Figure 4).

 

Figure 4: The impact and consequence of negative energy
Figure 4: The impact and consequence of negative energy

Another aspect to note is that metritis can differ in severity, a low grade case of metritis will generally clear itself having an impact on fertility but not on the level a severe case will impact. A much more severe case of metritis is often a result of other problems e.g. RFM, will need veterinary intervention and may take several months to improve if not spotted quickly. This will have a much larger influence on fertility problems. Figure 5 shows the effect of this.

 

This evidence shows how much of an effect mild to toxic metritis can have with a 30% difference between cows in calf by 150 days, however, the jump to a healthy animal is even larger with just above 70% of these being in calf by 150 days.

Effectively this will result in higher incidences of cull cows which would not be culled if managed correctly. Costs need to be applied to this and an average cost of 2.6ppl for the introduction of a replacement is shown by AHDB (N.D).

Since the cow is infertile the change can be warranted, however, this issue could easily be avoided through effective cow management thereby saving the farm the cost of a replacement and meaning either an increase in cow numbers or the ability to be able to sell dairy heifers.

If carried out correctly the cost of replacements can be reduced to 2ppl which will result in a gross margin increase of £90 per cow (AHDB, N.D.).

If you couple this with the fact that infertility is the single biggest reason for the culling of cows with percentages of 32.5% (Lari et.al. 2012) it is clear that big savings can be made. This further underlines the importance of keeping a healthy cow during the transition period.

Figure 5 Cows in calf by 150 days with varying severity of Post Calving Metritis (Pecsi, 2007)
Figure 5. Cows in calf by 150 days with varying severity of Post Calving Metritis (Pecsi, 2007)

In conclusion, this all comes down to transition management, and how cows are managed between drying off and the three weeks post calving. This is the most vital aspect of a cow’s lactation and must be managed accordingly. We should be spending 80% of time on this phase of the lactation which equates to about 20% of the cow’s entire lactation, the 80/20 rule.

This is the reasoning behind Wynnstay’s ‘Transition 80/20’ with products like Prepare nuts designed for effective dry cow feeding. Next month’s article looks at managing cows for good fertility after calving. In the meantime please note your own practices during the transition window, what do you do with the cows during this period? What are they fed? Where are they kept? How much space do they have available? Are they kept in separate groups? Next month we look at fertility through effective transition management and effective ways of managing fertility during the service period.

For more information on Fertility audits or for a full analysis of your transition practices through Wynnstay’s new DTSmetrics report please contact a member of the Dairy Technical Services team.

Written by Will  Astley – Dairy Technical Specialist

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