Farming Tips and Advice – Videos and Blogs from Tommy the Vet

Grass questions?

More questions than answers?


At a recent social event I met three farmers, all top class operators of spring calving, grass based systems. It was a very interesting discussion about the year gone by. Each had relatively good years but each also described individual problems they had encountered. While the problems were unique to each of them my experience over the last couple of years they are not isolated problems.

They each described the main issues they faced over the year.

  1. One had problems with weaned calves going backwards in April at turnout.
  2. The second had poor fertility or conception rates with a high empty rate of 13%, normally running between 6-9% in previous years.
  3. The third had an issue with weanlings succumbing to B1 deficiency in early august,


These three farmers had one thing in common they were all excellent at growing and utilising grass!

Now from the outset I know

A little about soil

A little more about grass

A bit about rumen health

A good bit more about animal health and performance

However when I see issues with health and performance you often have to work back right often even to soil health. It can be the building blocks of healthy animals. Therefore this article will look back and ask questions?

In Ireland our competitive advantage lies in the fact we have the ability to grow this cheap feed source from feb-Nov. Not only does it give us a huge competitive advantage but from a marketing perspective it must be one of the key cornerstones to our export story.

If you want to know how important grazing could be for our planet just checkout the work of biologist Allan Savory. Grazing can be vital to the sustainability of our natural ecosystems.

In Ireland we have become champions at grazing cows and utilising grass.

Regardless of the type of cow each farming system must utilise grass. We even have a state body which is world class in this area of research, envied the world over for what we have done over the last decades.

However a word of caution based on what I’ve seen in some clinical presentations about growing so much grass. It cannot be without some side effects, we must recognise these and be cautious about being blind to them. Of course we are now breeding a cow type better and more efficient at utilising grass. In fact these three farmers have been moving towards this type of cow.

Any time you question grass in any way it is almost like being unpatriotic. This is not what this article is about. Maybe I’m only seeing a minority and small amount of the problems but still from many conversations, these are not completely isolated cases. Of course these three cases were just that, conversations over a sociable beverage and not detailed farm visits.

Each of these problems could reflect issues around rumen health and function in my opinion. With all three cases I still have more questions than definitive answers. Although my suspicions get stronger the more conversations I have. Due to the fact that I think a lot of these problems are related to rumen function I’m going to start there.

The rumen or large stomach is an amazing organ, this large stomach where fermentation occurs turning grass and forage into digestible energy and protein.  A healthy rumen in simple terms requires many things to function well. Key to this digestive process is the microflora that are in the liquid raft of the rumen. These bacteria and protozoa breakdown the ingested forages into VFAs (energy) and amino acids etc. through fermentation. A heathy rumen will also allow an animal ruminate or regurgitate some of digesta to be further chewed producing saliva which further buffers and drives rumen health.

So in healthy cows we are not feeding the cow? Nor the rumen but the microflora in the rumen. We feed them and they produce energy and protein necessary for growth and production. (Oversimplified perhaps, as I hear people say what about NDRP……ETC.)

Another critical component to rumen health is fibre, the fibrous raft is critical again to these microflora, rumianation and rumen health.


Before tackling these three conditions let’s think about what a healthy rumen requires and why maybe grass at certain times might be causing problems for rumen health.

One big question I have is about a monoculture (ryegrass) being grown very fast. At certain times of year this grass is low in fibre, high in CLA (conjugated linoleic acid). We are pushing the physiology of the plant to it limits perhaps? Or is there a limit?

How can we grow grass this fast and expect all the micro and macro minerals not to be affected. How can soil keep up? I do believe that a lot of mineral issues we are seeing are potentially related to this phenomenon of fast growing grass and poor soil health? (Again a questions?).

Some have questions about nitrogen and urea application and its role in rumen health. Excess urea in the rumen certainly in my perspective cannot be a good thing especially around breeding time? If you combine high levels of blood urea with an energy imbalance this certainly cannot be good for the cow, conception or the early embryo.

If we look at the cow faeces at certain times of peak growth and see how lose their dung is? This loose dung for me does not represent full digestion and good rumen health. The question is this acceptable loss in performance because of the added benefits of grass as a cheap feed. Could we consider adding fibre to the diet at this time of year to buffer? I’ve tried lots from allocating straw after milking, to chopped straw/molasses, buffers and beyond. Definitely adding effective fibre in particular can be helpful. These are short term solutions could more sustainable solutions be around mixed swards?

Again I admit I’m seeing problem farms and for the vast majority this is not an issue.


So what about these three specific conditions I’m seeing more off, and these three farmers described to me?

  1. Rumen development: If you look at a developing rumen in a calf it requires starch and sugars to develop these large rumen papillae (folds) that help an increase absorption. It also requires fibre to aid and stimulate muscular stimulation and rumen enlargement (growth).

So lush spring grass could be potentially a problem for this developing rumen. It has sugars but also contains a lot of fats called PUFAs (polyunsaturated fatty acids) that are converted to CLA (conjugated linoleic acid). I read somewhere they can be up to 13% in spring grass which can’t be good for a young developing rumen?

These two combinations of oils(linoleic acid)and low fibre in some cases seem to halt and slow down rumen development. In some cases it can go backwards quiet quickly with calves wasting and scouring.

Of course there are many things that can cause scouring and wasting. However in a lot of these herd cases I’ve seen it is this form of maldigestion and rumen development failure. These calves often need to be bought in and put back on milk in some cases. If spotted early changing diet around can kick start a slow recovery?

There are many theories on this one? My strong suspicion is lush spring grass in some cases can be causing problems. There are others regards acidosis from meal feeding and maybe even some talking about viruses that might be contributing.

Again more questions than answers!!!

One thing that has worked for me is keeping calves on meal for longer and poorer quality pasture (what’s that in spring I hear you say). Feeding meal until rumen development at 6-8 months is not a waste of money particularly when you consider the benefits of feed efficiency in younger animals.

This is a conversation to have with your nutritionist, vet or adviser if suspicious!


  1. Poor fertility, BF crashing and SARA (subacute ruminal acidosis).

Like everything that could be affecting fertility in cows it is multifactorial. I have seen some unusual cases this year where scans weren’t where people would have liked and empty rates were slightly higher. In herds where BCS was excellent? From a weather perspective this year was spot on for cows. Schmallenberg viremias were discussed the usual infectious agents and mineral also. When these are ruled out you again have to look at energy and rumen health around breeding time and its potential role in affecting fertility. Ruling out the obvious thin cows, can this lush spring grass in some cases be affecting how healthy our rumens are? This for a period of 4-6 weeks could lead to a second drop into negative energy balance in cows (there is always a natural drop after calving). Of course a wet month or poor grass growth is probably a much bigger risk?

Even you see increases in PICA because of this where cows actively seek out fibre. Briars stones earth and plastic can be consumed. Of course this can be linked to low sodium or low phosphorous as well. Again growing phenomenon’s over the last number of years at spring time?

Also the questions around early embryonic losses and the effects of urea levels in blood I’m still no closer to saying yay or nay on this one? However high levels of blood urea coupled with an energy deficit is not a good combination for the young embryo in my opinion.  Some farms have seen a significant increase in bulk milk urea around this time where it’s being measured. Again how accurate or serious is this?

Maybe again Tommy is being a bit sensationalist and only sees the problem farms? I do question when you see how lose cows get in certain farms, combined with dropping butterfat’s. This for me is an indication of an unhealthy rumen.

When not severe it probably is an acceptable side effect (BF drop) to utilizing this green rocket fuel in early spring.


I also have seen a spike in viral respiratory disease in cows around this time of peak grass growth. When lung worm is ruled out, I often have my suspicions about this potential second energy gap in the lactation contributing to immunosupression? Could this open the door (drop in immunity) for viruses like RSV and PI3 which are circulating in many of our herds to start affecting cows at this time of year?


  1. CCN vitamin B1 deficiency

CCN (cerebro cortical necrosis) is a brain related disorder seen often in young calves and lambs sporadically. This occurs where there is a deficiency in vitamin B1. Over the last two summers I’ve heard a number of herd incidences of this disease with in some cases 5-8% of young stock affected typically in June-august.

B1 is interesting because it is actually the microflora in the rumen that synthesise it? Only when there has been something affecting these (microflora) do you often see this disease occurring. Up to 3 years ago I never saw this in anything but the odd case. So any disruption or massive dietary shift could predispose to it in the growing calf or lamb. The cases I’ve dealt with and heard of lately have been 2-3 weeks after shifting animals to more lush pastures. It is often the case the clinical signs will appear usually 2 weeks after a change of diet. It could also be induced in young ruminants by changing or increasing meal too rapidly.

In fairness these cases are more isolated than the previous two but still unusual to see an increase.


What can be confusing is there is still no defined patterns. Some farms with similar cows, similar grass, and similar fertilizers and are having no issues.  Maybe it’s all in my head??? I am interested in some research and work being done on mixed swards. It makes sense from the point of view of rumen health. This must be matched with financial and production output also of course, but should rumen health be added to this decision tree?

Our modern grazing systems are now the envy of the world no doubt. We must be mindful of how far we can push this without affecting the cow, the rumen and the microflora (remember we are feeding the microflora not the cow).

Lastly one real concern I have is the ever growing concern with parasites (what a depressing article I know). Our weather combined with higher stocking densities and tight grazing is playing into the hands of the parasites. Mix that with some very poor products (wormers) on the market you can have a dangerous cocktail on some farms.

We can do nothing about the weather nor should we change our highly evolved grazing strategies. However when buying a wormer the cost is not what you pay for it on the day, but the economic return from its strategic use? Your vet is best placed to help you make this all important decisions about dosing strategies based on farm history and some diagnostics.

This article is not a dig at anyone or any system. In fact as farmers we aren’t competing against each other, all be it maybe for the sake of our egos. This maybe only the tip of the iceberg stuff and deemed sensational, but remember the titanic. After all I’m just asking questions and maybe all I’m missing is the right answers?

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