Laura Chesters and myself are midway through our MBR, and our recent module raised some important issues around the involvement of nutrition in fertility management.

As farm vets we’re not often approached for nutrition advice, however, it is useful to get us involved when thinking about the wider picture. You’ll be aware that it’s not just about putting some feed in front of cows and hoping to get some milk out of them, it’s much more complicated than that.

They often say there are four diets fed to a cow:

  1. The diet the nutritionist puts on paper
  2. The diet the farmer puts into the mixer wagon
  3. The diet the cows actually eat
  4. The diet the cows manage to utilise

If your cows aren’t performing how you’d expect, then we can investigate in these four areas.

Nutritionist’s ration

This is basically your ingredient list. Nutritionists are very good at formulating rations and are much better than vets at knowing how to get there. They create a ration that provides enough energy and protein for an average cow in a particular group.

However, remember that each cow will have a different energy and protein requirement. She first needs enough for maintenance (to stay alive). She also may need to grow, lose weight or gain weight. Then she also needs to get in calf or grow her calf. And lastly we want enough leftover to produce milk!

So, when a ration is created it’ll be for the average cow to give a certain amount of milk, but as you’re aware, every cow is different.

Mixed ration

This is the ration that’s put into the mixer wagon and fed out to the cows.

Lots of things can go wrong at this stage, we may end up using a different cut of silage to what the diet was formulated with; there may be spoilage; and silage may be wetter or drier than we expected. Then we’re relying on the exact right amount of each ingredient to be put into the mixer wagon.

Eaten ration

There can be a large amount of variation in how much cows actually eat. This will depend on their stage of lactation, their body condition, their stage of gestation, and whether the feed is actually available to them! We’re formulating rations expecting that cows will consume a certain amount of dry matter, but once again, there is huge variation in cows’ capacities.

To allow cows to reach their expected dry matter intake, we need to remove any blockers to them achieving this. Notably, to reach these intake levels we need to allow ad lib eating. This is most commonly inhibited by cows not having enough space at the feed barrier, and therefore vulnerable cows getting pushed out so they don’t get their fair share. Feed needs to be freely available – it must be actually in front of the cows; fresh enough to avoid spoilage; well mixed; and regularly pushed up to help prevent sorting.

Diet utilised by the cow

This is harder to measure! With so much unpredictability further up the foodchain, we have to assess the cows’ performance. Are the cows doing as expected? Are they milking well? How is the overall fertility?

Some of you may have seen our production reports. These are produced from your milk recording data and with the data we can assess your ketosis or subacute ruminal acidosis (SARA) risk. Both of these use your fat:protein ratio to assess risk.

Additionally, cows with a butterfat >5.5% have a higher ketosis risk, as do cows with a protein yield <0.9kg, which is suggestive of negative energy balance and cows milking off their backs.

If we see cows with a low butterfat, <2.5%, this is an indicator of SARA. Faecal scoring and rumen pH testing can also help us to diagnose SARA.

We can also look at your fat:protein ratio; >1.5 would be an indicator of ketosis and <1 is associated with SARA.

Further investigation into how your cows are performing could include metabolic profiling through blood sampling, and can be a useful way to determine what might be going on.

If you’ve got any nutrition woes or you’re not happy with how your cows are performing, please get in touch as we’re always more than happy to help out!