Do dairy cows need calcium in late lactation?

 

Do dairy cows need calcium in late lactation?

Article supplied by S M Macky BVSc (dist), Director, Dairy Production Systems Limited

In theory, low producing cows in late lactation should be getting enough calcium from pasture to meet all their daily calcium needs. In reality, we see down cows with milk fever and cows with subclinical hypocalcaemia in late lactation, over the drying off period and even into the early dry period.

Obviously something is not going to plan. The main considerations will be:

1. There's not enough calcium in the cow's daily diet
2. She's getting enough calcium in her diet but isn't absorbing it
3. The cow's calcium requirements are higher than assumed
4. A combination of all of the above

Not enough calcium in the diet. The first problem, unfortunately common in New Zealand, is that the cow is simply not getting enough to eat to meet the needs of milk production, foetal growth, body condition gains, activity, growth, weather problems, etc. Most of our pastures contain enough calcium for late lactation needs in a normal, healthy, well grown, well-conditioned cow, so if pasture dry matter intake (DMI) is adequate ( 3 - 3.5% of mature bodyweight) and pasture calcium content is above 0.5%, theoretically she will be getting enough calcium. Note that calcium content may be diluted in fast growing grasses.

Problems arise when the calcium content of the diet is too low and/or total intake is too low. If the cow's intake is not solely pasture but includes grains, cereal silage, maize silage or any other low or marginal calcium-containing feed, such as palm kernel expeller meal, then her total daily calcium intake will fall. Calcium will need to be supplemented.

In certain circumstances calcium may not be well absorbed from the gut, or if absorbed may be rapidly excreted or otherwise made unavailable to the cow. Depressed rumen pH, i.e. subclinical or clinical rumen acidosis, even transiently each day, can result in depressed uptake as calcium may 'pool' in the gut. Calcium excretion by the kidneys may be increased.

Lush, fast growing grass after the autumn flush, especially nitrogen boosted young grasses and annuals are common culprits, especially if not accompanied by adequate physically effective fibre. These problems are exacerbated where low calcium, rapidly fermented feeds are improperly introduced, rates of feeding are increased too rapidly or slug feeding occurs

Excess zinc and/or magnesium can also cause hypocalcaemia. Diets high in unprotected fats and oils can reduce calcium availability to the cow, as calcium may form 'soaps' with the fat or oil which may not be able to be dissociated and absorbed in the lower gut.

Increased calcium needs can be numerous and interrelated, eg:

• Need to replenish bone calcium reserves, foetal growth
• Need for continued growth (most New Zealand cows are not skeletally fully-grown even as 4 year olds)
• Meeting activity needs, e.g. walking, trucking, fighting
• Adverse weather events
• Jersey cows have an increased susceptibility to hypocalcaemia
• High risk milk fever farm, e.g. high potassium feed at calving
• Calcium reserves must be replenished before dry off
• Stresses, such as dry off, new feeds, new mobs

Most often when we look at health and productivity in late lactation, especially when looking forward to avoiding problems in the next season, most New Zealand cows would benefit from an improved calcium intake in late lactation. Too often, it is assumed that because it is the end of the season, calcium supplementation is not required. The clinical problems we see are only the tip of the iceberg. Rates of supplementation may not be as high as needed in early lactation but getting it wrong can be just as costly. Many of those potential problems may not be seen until the next season!

Equestrian Cow

http://www.barnmice.com/video/udderly-amazing-girl-teaches

Cows and Co2

NZCPR Guest Forum  Opinion piece by Robin Grieve 4 April 2011 The folly of the ETS

The Emission Trading Scheme was put in place to help New Zealand meet its obligations to the Kyoto Protocol. The ultimate purpose of that Protocol and the ETS is to reduce emissions of greenhouse gases that some say may be causing global warming.  While I find it extraordinary that our Government is prepared to impose costs on its people based on nothing more than a theory, the focus of my concern is the way in which the ETS treats livestock emissions of methane. While the debate over global warming may never be finished, the way livestock emissions of methane are treated clearly demonstrates the folly that is the ETS.

The problem lies in the way the ETS is focused on what they call carbon emissions. The carbon they talk about in the ETS, is not the atom Carbon, or the molecule Carbon dioxide, it is a unit called a ‘carbon dioxide equivalent’. It is a theoretical or virtual unit and not representative of anything real. This is because while the values assigned to something real are always set by nature and inarguable,  the values assigned to virtual units like these carbon dioxide equivalents are set by politicians, and can differ hugely depending on what is included in the calculation and what is not.

As an aside, I believe using the term ‘carbon’ when referring to these carbon dioxide equivalents is sloppy. It is a good marketing ploy though for the global warming industry because it conjures up images of something black and sooty and bad, which of course it is not.  For purpose of clarification when referring to these virtual units I will use the proper term of carbon dioxide equivalent. When I refer to carbon I will be referring to real atomic carbon.  

In the New Zealand Inventory of greenhouse gases agricultural emissions make up 48% of New Zealand’s total emissions of these carbon dioxide equivalents but this does not reflect the reality of what is happening in our atmosphere in terms of real greenhouse gas. 

The main greenhouse gas that livestock produce is methane.  Methane is produced in the rumen of a ruminant as a by product of the digestion process. It is called enteric methane and is released into the atmosphere when the animal belches (they do not fart).

Enteric methane makes up nearly one third of New Zealand’s emissions of carbon dioxide equivalents, but most if not all of this methane has no effect on the atmospheric concentration of methane or any other greenhouse gas in the atmosphere.  It does not cause an increase in the concentration of methane, therefore it does not cause an increase in the global greenhouse affect and therefore it can not physically be responsible for any global warming that may be happening.

The reason for this is that methane (CH4) oxidises to CO2 over a relatively short period of 8-12 years. Because it is continually breaking down to CO2 it needs a constant source to replenish it and maintain the atmospheric concentration. A steady state of production only maintains current levels in the atmosphere, it does not increase it. Most if not all enteric methane produced in New Zealand is from a steady state of production and is not an anthropogenic activity as defined by the UN.

Climate change as defined by the UN and The Inter Governmental Panel on Climate Change is “A change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere”.

According to the UN definition, for an activity to be causing global warming it has to alter the composition of the atmosphere. For an atmosphere to be considered altered it stands to reason it has to be different after the emission than it was before the emission. In the case of enteric methane the atmosphere is not different, it has no more CO2, CH4 or C in it than it had before and it is therefore not altered and methane emissions from a steady state source are not an anthropogenic activity.

For this reason almost one third of the emissions New Zealand reports in the Inventory of Greenhouse Gases should not be in there. Including them in the ETS was a mistake making the ETS, which is a major economic policy of this Government, fundamentally flawed.

To understand how this mistake came about we need to understand how carbon dioxide equivalents are calculated. Carbon dioxide equivalents were invented to try and quantify the greenhouse effect of a number of different greenhouse gases. The greenhouse effect of all greenhouse gases is equated to the greenhouse effect of CO2. Methane is better at trapping heat than CO2 with onemolecule of methane having the equivalent greenhouse effect of 21 molecules of CO2 when this effect is averaged over a period of 100 years. For this reason methane has what they call a global warming potential of 21 and so an emission of 1 tonne of methane is quantified as 21 tonnes of carbon dioxide equivalents. To quantify the different gases in this way does makes sense and on the face of it is a good idea but in reality it does not work. There are a number of reasons for this, not the least being it fails to take into account the cyclical nature of livestock emissions.

When an animal eats grass and produces product it is part of the carbon cycle. During this process carbon in the form of carbon dioxide is removed from the atmosphere to grow grass. After the animal eats the grass most of the carbon is returned to the atmosphere and reforms immediately as CO2. It returns to the atmosphere through animal respiration, waste, and product eaten by humans who return it through their own respiration and waste processes.

Exactly the same amount of carbon has been returned to the atmosphere as was removed, making the animal truly carbon neutral. What complicates this though is that this carbon was all in the form of CO2 when it was removed from the atmosphere and while most of it returns as CO2 a small portion returns as CH4 (methane). This is where these imaginary carbon dioxide equivalents are created. When an animal converts a molecule of carbon dioxide to a molecule of methane the global warming industry say that one carbon dioxide equivalent was removed from the atmosphere as the CO2 molecule and twenty one carbon dioxide equivalents were returned as the CH4 molecule. Twenty additional carbon dioxide equivalents have been produced and released into an imaginary atmosphere. In reality though there is no more carbon, carbon dioxide or methane in the real atmosphere. There can be no global warming from them.

In short these carbon dioxide equivalents are a joke, they do not work. The UN acknowledges there are problems with them and set up an expert group to devise an alternative way to calculate them. They have not as yet found a metric that satisfactorily quantifies the greenhouse effect of a mix of greenhouse gases without causing anomalies as the current system does with enteric methane.  Designing an ETS around a system and methodology that is so flawed was not a prudent move by the New Zealand Government. What would be prudent would be a scientific review into the true effect enteric methane emissions are having on the atmosphere. John Key and Nick Smith have refused to do this preferring to spend tens of millions of dollars in a forlorn search for ways to mitigate the emission of a gas that is only harmful in an imaginary atmosphere not a real one. Their ETS is equally forlorn as a policy because it is based on methodology which is not scientifically credible