Review of Clinical Club Meeting with Richard Cooper of EBVC
This was a very informative talk from Richard Cooper (of the Evidence Based Veterinary Consultancy), a veterinary nutritionist who does copious practical research in this area as well as first opinion on farm nutritional advice. He also teaches vets and nutritionists.
Here are the basic points that we all need to know:
- Blood flow through the liver
An average high yielding dairy cow will consume around 25kg DM per day. Some particularly high yielders can eat as much as 28kg DM per day. This means that the liver is working extra hard to metabolise all the energy the cow is consuming. The increased blood flow through the liver means that the hormones are metabolised more quickly - hormones such as progesterone........the long and short of it is that the high yielding cow is likely to have less circulating progesterone and therefore will find it harder to establish and maintain a pregnancy.
- Fat breakdown.........what really happens
A dairy cow pre calving needs around 105MJ of energy per day. 1 week post calving, when she could be giving as much as 30 litres, the same cow needs 200-300MJ per day. Her dry matter intake (DMI) simply cannot keep up with this. So the fat tissue is broken down into Non esterified fatty acids (NEFAs). These NEFAs are then adapted in the liver to make glucose available to the cow. If this fat breakdown is happening too quickly and her system cannot keep up, the result is that ketones are produced. Any tissue in the body can use ketones as an energy source except the brain and the udder. On the outside, we see the cow losing flesh, her body condition falls and she begins to look plain.
When the production and use of ketones slows down, it is stored as triglyceride in the liver. Basically, the liver becomes stuffed with fat. If >5-10% of the liver consists of fat, this is known as Fatty Liver and is surprisingly common in dairy cows with around one third of cows going through this at some stage. 10% of cows will suffer from severe fatty liver. Fatty liver results in decreased liver function which reduces fertility homone production further.
An added insult to the whole process is that NEFAs are toxic to embryos. This means that if you have just managed to get a cow pregnant when she goes through all this, then the presence of NEFAs could cause embryo loss. And a final addition to this is that NEFAS are also thought to affect the quality of uterine fluid by affecting the acid-base balance. Again, this is not a friendly environment for an embryo to develop.
It should be borne in mind that eggs are "primed" 3 months in advance of their ovulation. Therefore an insult NOW will affect the cow getting in calf 3 months later. So remember that, if we are trying to get a cow in calf 100 days post calving, 3 months before this will be about calving time when all the NEFA insults are likely to be affecting her.
- Ways to close the Energy Gap
- add more fat and starch. The main problem with this is that it is expensive and we have to be careful to avoid SARA. Also, a point worth noting here is that, if the rumen is acidic (ie from lots of starch) then this will cause the protected fats to disassociate and they will end up as free oils in the rumen. The other problem with some protected fats is that they are not very palatable.
- enhance DMI. We need 235MJ to produce 35 litres. A quick calculation will tell us that at 17.5kg DMI we will need 13.4MJ/kg. AT 19.5kg DMI, we will need 12MJ/kg. At 21.5kg DMI, we will need 10.9MJ/kg. Are you getting the idea??!! We can avoid feeding rocket fuel by increasing DMI.
- Maximising Feed Intake
These are all the points which everyone knows we should be doing but which very few people do. But it is these things which will make the all important difference to how many MJ a cow can consume.
- fresh and dry cows need 80-100cm of feed space.
- highs need 60-70cm of feed space per cow
- cows should ALWAYS have food in front of them
- push up the feed 4-6 times daily
- feed a palatable ration to the dry cows as this sets up the DMI for their lactation.
- if you have to feed dries every other day (not to be recommended), feed a dry feed such as good quality hay and dry cow rolls
- ensure there is some form of fermentable carbohydrate provided to the dry cows in order to prepare them for the milking ration. The best quality protein would be Soya as opposed to urea/rape which is less palatable but is cheaper.
- Fat Cows- how to handle them
Of course, the best way to handle them is to avoid getting them at all. However, in real life, this is impossible. If you get them, the best time to diet them is in late lactation. One way of doing this is to increase the protein, reduce the energy and try to get them to turn their extra weight into milk. If this group is being fed for 33 litres, however, this is clearly not going to happen. If you can't cater for them milking, then dry them off early and put on a low energy, straw and mineral diet.
Have you ever wondered why cows mobilise too much fat? The answer is that too much starch makes them metabolically lazy.
High levels of urea are proven to affect embryo quality (Butler et Al, 2005). Low quality protein, without enough energy could lead to high blood urea levels. If bulk urea levels are over 0.038%, intervention is required.
- Fats and Fertility
Fats decrease progesterone clearance which is a positive thing if we are trying to get a cow pregnant. Fats are also handy to help close the energy gap (see earlier).
- Vitamin E and Selenium
This is often underfed in dry cows. there should be 6666iu/kg of vitamin E and 25-32iu/kg in 100g of dry cow mineral so this is always worth a check.
- Dietary Starch
Starch can reduce egg quality and also viability and also reduce embryo development. In addition, it can mean a reduction in DMI and can increase rumen dysfunction. On the other hand, starch can speed up return to cyclicity and will ensure increased levels of progesterone in the liver. So, in summary, some is good but more is not necessarily better from the fertility point of view! A recent study has shown that a high starch diet in early lactation and lower starch diet coming up to calving improves fertility in the next lactation. It also shows that, in a nutshell, high starch in fat cows is a metabolic disaster........common sense really!