Fertility in Dairy Cows-The Bigger Picture Part 3

Managing transition cows- Key to Success

In last months’ article I looked at the transition problems that cause fertility issues with dairy cows. In this article I will look at how we simply reduce these problems through effective late lactation, transition and early lactation; the basis of Wynnstay’s 80/20 concept. Before bringing the article to a close with an assessment of how effective dry cow management can have a positive impact on fertility.

We begin before the cow even reaches her transition period, this is a crucial point for any dairy cow as it can have a direct effect on how the cow performs during both the transition period and her subsequent lactation. At this point in her lactation the cows Body Condition Score (BCS) is vitally important. We need to be aiming for a BCS of 2.5-3 during the dry period. To achieve this we need to have the cow in the right condition before she is even dried off, maximising both cow health and performance.

It will also improve efficiency within the dry period as feeding a cow to gain condition during the dry period is costly, as well as this cows fed too much will put more nutrients into the growth of the calf resulting in more difficult calving.

This has one of the biggest impacts on fertility with cows open for 33 days longer, than cows which had a trouble free calving (Dematawena and Berger, 1997).  Whilst this is true of thin cows a fat cow will have reduced intake, which will cause problems post calving with a higher incidence of metabolic issues.

Cows should be checked at 8 week intervals in order to allow changes to be made to get cattle to the right condition before dry off. Wynnstay’s DTSmetrics offers this service through its data analysis by looking at fat and thin cows allowing farmers to change their system in accordance with results.

Next is lameness.

This is the second factor that has an impact on the dry period and ultimately fertility. A lame cow during the dry period will have reduced appetite and reduced intake as well as a reduced intake post calving. Which impacts on the time spent in negative energy balance (NEB) and also the activity of the animal meaning signs of heat will be much harder to spot even with aids. Lameness has been shown to be the biggest cause of missed heats with cows classified as lame from the beginning of the dry period to the end of the Voluntary waiting period (VWP) (time between calving and first service) having 3.5 times greater odds of delayed cyclicity (Garbarino et.al. 2004).

The same study also showed that if lameness had been prevented in these cows then the likelihood of delayed cyclicity was reduced by 71%. This is another aspect that is monitored through Wynnstay DTSmetrics allowing farmers to monitor lameness closely.

Days to First Oestrus in Cows
Figure 1-Days to First Oestrus Indoor vs Outdoor Dry Cow Management

The next stage is the dry period and the management of both far off and transition cows. The starting point for this is the feeding of the dry cow. This can have a major impact and with the current volatility in the milk prices more people are going to be tempted to turn dry cows out to grass.

Although this is a cost saving measure the question is will it save enough to warrant the added cost of a longer period till conception? A study done by Astley (2013) showed that cows fed on a grass based diet took 34 days longer to conceive, had a 7 day longer period to first service and 0.8 services more per conception (see graphs below).

So what are the options available for indoor dry cow management?

One to consider is a DCAB diet. This increases the acidity of the blood forcing the body to mobilize more calcium from the bone. Delayed mobilization of calcium from the bone around calving is the cause of milk fever. On a DCAB system the body is already mobilizing calcium from the bone long before parturition.

This system can run effectively as a Semi DCAB also and reduces the risk of the blood becoming acidic.

Wynnstay’s 80/20 prepare nuts allow farmers to do this being a semi DCAB nut which also contains dry cow minerals and good sources of protein and starch which are crucial to a dry cow.  Along with this DTSmetrics monitors the transition cows more closely allowing farmers to make small alterations to their transition management if required, looking at rumen fill, dung quality and diet consistency as well as other aspects.

Calving Conception
Figure 2-Days to conception Indoor vs Outdoor Dry Cow Management

The final point to consider is the three week period after calving.

We need to promote intakes post calving in order to reduce the effects of NEB, therefore we should be formulating diets to include the best forages to increase palatability and intakes.

Preferably fresh cows should be in a separate group with a low stocking rate. However if this isn’t possible stocking rate should be kept below 90% across the whole herd in order to maximise fresh cow performance and ultimately improve fertility.

 

What impact is all of this going to have on fertility? What are the cost benefits of operating an effective dry cow management protocol?

As discussed already an indoor dry cow management system is going to cost more on a daily basis if we factor in the cost of forage a grass based dry cow diet will be 90p less per day however every day a cow is open costs a business £3.10. So if we consider the data shown earlier in the article the additional cost of an indoor dry cow management system is £50.40 however the saving made in days to conception is £102.

Therefore keeping dry cows indoors on a controlled diet has already paid for itself without considering increased incidence of metabolic issues. This is an important point to consider given the current milk price situation as each cow kept on an indoor dry cow system will generate £50 more revenue.

We also need to consider reducing NEB post calving. Very few studies have been done on the effect of NEB on fertility however Reist et. al. (2003) showed that cows experiencing prolonged NEB took longer to first oestrus and longer to conception.

This was confirmed by Patton et.al (2007) who proved that cows not showing visible signs of NEB were more likely to hold to first service. Couple these findings with the data we now have available through reports such as CowWatch which tells us how long cows are in NEB, we get a clear indication as to how soon cows will conceive.

There is an argument to suggest that if there is a higher period of NEB you should increase the VWP from 42 to however many days it takes the cows to come out of NEB on average. So let’s say that you set your VWP at 70 days this is going to cost you £84 over the extra 28 days you leave the cow empty compare this to the cost of a straw of semen at £20, it is clear that it is worth serving cows earlier even if time taken to come out of NEB is poor since the cost of extra days far outweighs the cost of the semen to serve the cow.

Even so we shouldn’t be accepting long days of NEB and should be reducing it to around 40 days in order to allow better conception rates earlier. However there are a few exceptions to this rule with herds that have exceptional fertility extending the VWP which will allow cows to achieve peak milks leading to more milk production throughout lactation, if this is not done cows won’t achieve peak milks and yields will be compromised. The other side of this is if the cows have a massive issue with NEB then the VWP will have to be extended until the issue is addressed.

So in conclusion in order to achieve improved fertility we need to improve management of the dry period.

It has been made clear that there are three major aspects that will impact on fertility post calving during the dry and transition period. The first of these is metabolic disorders as discussed in the previous article.

The second is how we manage our dry cows, making sure they are not over conditioned or lame and keeping them housed throughout the dry period.

Finally is minimising NEB through effective transition management. If we get all three aspects correct then fertility will improve.

In next month’s article given the current milk situation I will look at ways of saving money through fertility.

Written by Will  Astley – Dairy Technical Specialist

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