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article by Roger Martyn

Given the right weather conditions and good pasture quality, a seasonal milk dairy herd in full production can readily average 1.75 kilograms of milk solids (kg ms/day) production per cow daily on an all pasture diet. This should be achievable for more than just a few days during the season.
While research shows that the average commercial dairy herd certainly has more than enough genetic merit to achieve these levels of production on a pasture only diet, many farming situations struggle to achieve this.
Why is this? For many it is simply a matter of them not ‘fully feeding’ their cows. Fully feeding cows involves more than just opening the gates and letting it rip. While this strategy might well achieve the desired daily production targets in the short term, experienced herd managers will soon tell you that having the confidence to do this on an ongoing basis without fear of running out of feed is another thing! So, is there in fact a way to fully feed your cows with confidence?
I have nominated the following factors as being the most important in fully feeding of cows.
• Pasture allocation knowledge and skills
• Maintaining pasture quality
• Maintaining appropriate cow condition
• Identifying pasture surpluses and deficits

Getting all of this right is the key to sustained high daily milk solids production. This is no mean feat but it can be done! For this article, I’m going to focus mostly on the first factor – that of allocating pasture and how to ensure your cows fully feed on what is presented to them. The lessons learned from this getting this right will prepare you well for mastering the other factors mentioned.

Getting a Cow’s take on things
To get your herd averaging 1.75 kg ms/cow/day, the boffins tell us that a modern dairy cow of average genetics is required to consume around 18kg of quality pasture dry matter per day (kgDM/cow/day).
Consider for a moment, what consuming 18kg dry matter of growing pasture actually means to a cow. A typical spring pasture has a dry matter content of around 17%. This translates to 105kg of ‘wet’ matter – the actual weight of the grass we’re expecting the cow to eat over the day. That’s about the weight of a 200 litre drum half full of water! Rapidly growing spring pasture can have an even lower dry matter content which can increase the consumption task markedly. For example, spring pasture with 15% dry matter would require the consumption of 120kg of ‘wet’ matter to meet the same 18kg dry matter intake task. Considering the large amounts concerned, it should also come as no surprise that 18 to 19 kg of dry matter in the form of actively growing pasture is nearing the limits of what a 500kg live weight cow can physically consume during any one day.

Getting the Farmer’s take on things
Let’s calculate the grazing area requirements for a well producing milking herd using our 18kg dry matter of pasture benchmark.
The boffins suggest milking cows should go into pastures with a cover of around 3000 kg dm/ha and leave the pasture with a residual of at least 1500 kg dm/ha.

This implies there will be 1500 kg dm/ha of pasture available for consumption.
(3000 – 1500 = 1500)

Since there are 10,000 square meters in 1 ha, this implies there will be 0.15 kg of dry matter in just one square meter.

(1500 ÷ 10,000 = 0.15)

If a cow requires 18 kg dm of this pasture to produce the 1.75 kg ms in one day, she will therefore require 120 of these squares or 120 square metres per day.
(18 ÷ 0.15 = 120)

120 square metres is actually a large area. Herd managers are often shocked to see that it is this sort of pasture area that is actually required to meet these feed intake targets.
So for every 100 milking cows, 1.2 ha of pasture will need presenting daily to meet the 18 kg dm pasture allowance. In typical stocking rate situations, this will soon have the farm in a grazing rotation of 20 days or less, a situation many herd managers find unnerving.

A couple of points require highlighting here.

Firstly, herd managers often underestimate the actual area of pasture required in order to ‘fully feed’ their cows when assessing feed requirements purely by eye. The correct solution is to measure the amount of pasture using a pasture measurement tool. The GrassMaster pasture meter an ideal tool for this. It is simple to operate, quick to use and its operation is consistent.

Secondly, herd managers often lack the confidence to continue fully feeding their cows once they find how fast the grazing round has become.
Their solution is to get proficient in forecast feed budgeting.
It is really only through combining pasture measurement with forecast feed budgeting that the potential of converting pasture into animal production can fully realised.
It is this that can provide a herd manager with the confidence that sufficient pasture will be available come next round. Pasture measurement and feed budgeting also assist in identifying pasture surpluses or deficits and to make decisions of when to shut up pastures for silage or hay, to start feeding out supplements, adjust stocking rates, dry off cows, and identify those pastures that are due for re grassing and so on. Feed budgeting also provide useful indicators such as the ‘average farm cover’ and ‘average daily pasture growth rates’ which are useful benchmarks as to how the season is progressing.

Rising plane of nutrition
Herd managers often restrict their cows feed intake immediately prior to calving in order to prevent calving difficulties and to ensure there will be plenty of feed for the milking herd. Both are of doubtful merit. A difficult calving can be more often attributable to a cow’s lack of energy due to malnourishment prior to calving than to the size of the calf. In order to avoid calving problems, it is preferable to make sure cows do not get over-fat earlier on in their pregnancy and for the selection of sire breed and size characteristics to correctly match that of the cow’s and her age.
It is preferable to feed cows on a rising plane of nutrition managers immediately prior to calving through supplementing 2 to 3 kg extra dm feed above maintenance in the form of a feed that stimulates rumen activity and stretches the stomach. Hay is a good option for this. This rising plane of nutrition helps get the cow used to eating the increased feed volumes required of her for post calving milk production without robbing her the energy required to have a successful calving.
A rising plane of nutrition also helps a cow reach a higher peak of milk production and research shows this also results in a higher production trajectory for the remainder of the season meaning higher overall production, that is, so long as the feed can be kept up to her!

Cows enjoy food variety as well

Pasture palatability is an important consideration in maximising feed intake. Cows are no different to humans in enjoying the taste of their food. Cows prefer the leafy portion of pastures which perhaps unsurprisingly is also the most nutritious. Therefore providing pasture allowances where the cow has to only choose the leafy portion will result in increased pasture intakes.
Cows also enjoy a variety in their diet, just as humans do. Incorporating a variety of improved pasture species into seed mixes for over sowing and pasture renewal can improve pasture palatability and animal performance. Alternative pasture species such as prairie grass, phalaris, fescues, cocksfoot, and chicory should be considered too. These offer benefits besides improving pasture palatability and variety. These include seasonal growth advantages, greater tolerance to wet or drought or pests and many offer improved harvesting characteristics for a cow. It is worthwhile mentioning too, that having the odd ‘weed’ present in pastures is not necessarily a bad thing. Weeds also provide feed variety for cows and as old timers will testify, are often the preferred diet of unwell cows seeking to self medicate.

Causes of poor pasture palatability
Sometimes it happens that cows simply do not like eating a particular pasture. This is invariably a palatability issue. One cause can be that the pastures have high nitrate levels, as can happen following nitrogen fertiliser applications, or following recent rains after a prolonged dry period. High potassium levels can be another reason for poor pasture palatability, and again this can occur after potassic fertiliser applications and also after prolonged dry periods followed by rain. Sometimes newly established pastures will have poor palatability, usually due to high nitrate levels. In other instances, the poor pasture palatability can be simply due to a lack of lime.
A correctly taken herbage test in conjunction with a soil test can soon confirm poor palatability suspicions. This could be done in conjunction with the use of an optical brix-meter that measures a pasture’s soluble sugars and with experience provide a quick and cost effective way of indicating the nutritional and palatability state of a pasture.
Often all that is required to improve a high potassium related palatability problem is an application of fertiliser grade salt at 25 to 50 kg/ha rates, with palatability improvements being apparent as soon as just a few days after application.
Where herbage tests indicate low calcium levels and soil tests indicate low base saturation levels applications of lime will have similar beneficial effects.
Applications of liquid seaweed fertilisers often result in improved pasture palatability although an application of solids composing of a correctly recommended mix of lime, minor and trace elements will have far longer-term beneficial results.
Pastures exhibiting high nitrate levels should only be grazed in the afternoon as this will be when the sugars are up and nitrates down. Grazing such pastures on cloudy or overcast days should be avoided.
Cutting a portion of the pasture (eg a third of a paddock) in the afternoon when the plant sugars levels are at their highest ( and nitrates lowest) and leaving this to wilt improves the palatability while the wilting facilitates greater pasture intakes. Allow access to whole pasture (cut and non cut) as some cows will still prefer to eat non cut pasture while others will prefer to eat only the wilted. The second and third portions of the pasture can then cut in following grazing rounds. This is also a great way to deal with pasture clumping issues, and is certainly a much ‘cleaner’ ways to top pastures in order to maintain feed quality than carrying out the task immediately after cows have left the pasture!

Balanced fertilisers
As inferred, soil fertility and fertiliser applications have significant implications on pasture palatability and pasture nutritional value so is another factor to in fully feeding cows. In short, balanced fertiliser programs are the starting point for nutritionally balanced pastures. This means utilising herbage tests in conjunction with soil tests. Soil tests alone are poor indicators of the status of important minor and trace elements and are unable to accurately measure some. Herbage tests are in most instances, better indicators or the minor and trace elements besides showing what the plant actually takes up. Ideally, a balanced fertiliser program should be based on field observations of the soils, pastures, grazing practices, and animals, coupled with herbage, soil and animal blood tests. Unfortunately, the expertise to bring all these together tends to be few and far to find. Balanced fertilisers go beyond a 30% potassic super mentality. In order to be balanced, fertilisers invariably need to contain some of the minor and trace elements beyond the NPK’s. It should be appreciated that lime is a fertiliser in its own right. Getting the balance right with fertilisers can vastly improve pasture palatability, pasture intakes, animal health and production. It can also result in a much more active soil life and pastures that are quicker to recover from adverse events such as pugging, flooding and drought.

Water, clean, and plenty of it
Given that water is the major constituent of milk, access to drinking water is an obvious consideration when it comes to fully feeding cows. Water must be readily accessible to all cows, so must be of ample flow, of good quality and be palatable. Accordingly, attention must be paid to the size of water troughs, to their placement within a paddock, and subject to a maintenance program that keeps them clean and free from bird and cow fouling all-year around. If a herd’s access is restricted to water or a herd even perceives their access is threatened, aggressive bullying behaviour by dominant cows is likely causing individual cows to miss out drinking and to become stressed and agitated. The results of this will be soon be seen in the milk vat.

The role of sodium in heat regulation

Sodium, potassium, calcium and magnesium all have roles to play in the body cells of a cow. In particular, they are important players in maintaining a cells structural integrity and in facilitating the transportation of food and waste products into and out of cells. The source of these minerals is largely reliant on a cows diet and while the cows is able to maintain the correct levels at the body cell level, excesses of one of them in the diet can cause the displacement and therefore deficiencies of others. For example milk fever can be caused by a lack of calcium and magnesium in a cow’s diet but these deficiencies can also be aggravated by excesses of potassium in her diet.
In an all pasture diet, sodium can have a big role to play in helping a cow maintaining the correct equilibrium of these other minerals at cellular level. This is because a cows diet is often excessive in the amount of potassium it contains, and accordingly low in the likes of sodium, calcium and magnesium.
Potassium is normally applied as a fertiliser to pastures in order to encourage clover growth which has a far higher requirement for potassium than grasses. Potassium is readily taken up by grasses and in quantities that are far in excess of their minimum requirements for growth. A result can be a pasture diet that far exceeds a cow’s nutritional requirements for potassium.
The situation isn’t helped in that grasses are poor harvesters of sodium and the presence of plant available potassium in a soil reduces the availability of plant available sodium in the soil even further. Sodium is also very mobile within the soil so is easily lost to leaching. The overall result can be a pasture diet that is too high in potassium and too low in sodium to meet a cow’s nutritional requirements. The situation will be aggravated even further if maize is part of a cow’s total diet since maize is naturally very low in sodium. Sodium is also removed from a cow’s body in their dung and urine and milk with very high levels removed during mastitis events.
A lack of sodium usually manifests itself visually in a cow as one showing a dry muzzle, a rough and hairy coat, and one that is prone to heat stress with an associated loss of appetite.
Common salt (sodium chloride) can play an important role in helping a cow cope with these sodium imbalances. Cows can be supplemented salt by daily drenching, by sprinkling of salt onto feed supplements and by been given access to loose salt. However by far the most convenient and effective means is introducing salt is via their drinking water. Dosing of water troughs or use of in-line dispensing systems are ways of doing this. Good advice should be sought however on dosing rates and dispensing regimes.
Cows that have sufficient access to salt can cope with heat stress much, much better resulting in improved feed intakes and milk production. Visually such cows will display wet dewy muzzles, have sleeker more shiny coats, and display plenty of saliva production when grazing. Interestingly, such cows also attract fewer flies!