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Keeping the Energy Balance Neutral Through Transition

Published 8 September 09

DairyCo's Adam Clay looks at how carefully managed nutrition can carry cows through transition smoothly, sustaining fertility and maximising productivity. The transition period is one of the most important times to manage feeding effectively.  With careful management and attention to the cow's condition and nutritional needs farmers can ensure that a cow's energy balance is kept at a level that sustains both fertility and productivity.

Dry cow period

Many trials have been conducted on dry cow period length in an attempt to increase intakes post calving, but there is no real agreement on what the answer is.  Shorter dry cow periods have resulted in early lactation yields being reduced by 10%, but because of the shorter dry cow period and longer lactation, overall yield has been found to be very similar.

Milk Production with Different Dry Periods

Days Dry

0

28

56

Milk production at end of previous lactation (Day -56 to Calving)

750

422

0

Milk production at start of current lactation (Days 1-70)

2373

2653

2971

Total yield over trial period (Day -56 to Day 70)

3123

3075

2971

Source: Rastani et al (2005) Journal of Dairy Science 88, 1004

Yield aside shorter dry periods have been shown to result in a higher pre and post calving dry matter intake which has resulted in a reduced negative energy balance, this can have a knock-on effect on improving fertility results.

Body Condition & Fertility with Different Dry Periods

Days Dry

0

28

56

Body Condition Score loss (Calving to Day 70)

0.56

0.81

1.37

Days to first ovulation

13

24

32

Days to first service

69

68

75

First service conception rate

55

26

20

Source: Rastani et al (2005) Journal of Dairy Science 88, 1004 and Gunman (2005) Journal of Dairy Science 88, 2401

If you are considering choosing a shorter dry period then it's important to monitor mastitis and cell counts beforehand, only cows with a cell count lower than 200,000 should be considered for a short dry cow period, even then they should pass a California milk test.

Feeding

Dry cow diets will vary from system to system and it's unlikely that we'll ever find one diet that will work every time on every farm.  However, there are a set of rules that all systems should abide by to maximise performance. Make sure you measure intakes to ensure dry cows are not being under or over fed.  A good rule of thumb is that a typical Holstein/Friesian should eat 2% of their bodyweight in dry matter. So a 600kg cow should eat 12kg DM/day.  Within a diet this should equate to energy intakes of 100 MJ ME/day through the dry period.  Where animals are split into groups, the far off period should receive 90MJ and the close up group should be moved up to 120 MJ to support the growing calf.

Protein levels should be formulated to 13-14% (130-140g/kg) in the dry matter, and unless dry cows are losing weight then I'd suggest that expensive undegradable protein is rarely required. Weight gain through the dry cow period should be kept to a minimum to avoid excessive calf growth, and also to avoid over conditioning which can have significant effects on post calving intakes and fertility results.

If a cow does gain weight, and calves down overfat, her dry matter intakes will be lower to start with, and as a result she will be in severe negative energy balance.  This means she will burn more body condition (milking off her back) which will leave a deposit in the liver called adipose tissue, this fat clogs the liver causing 'fatty liver syndrome', and may turn ketotic.  This has the effect of reducing insulin development, which is important, as this normally feeds the egg, making it viable for fertilisation, and a less viable egg will reduce the chances of conception.  

It is also important to avoid weight loss through the dry period as the beginning of the fertility cycle does not start at calving, the first follicle is created approximately two weeks pre-calving, so weight loss in this period results in a negative energy balance which can effect the viability of the eggs produced. For this reason it is essential to dry cows off in the correct body condition score of 3 (2.75 is acceptable for some weight gain, 3.25 is also acceptable but you must be sure to minimise weight gain through the dry period).  Ideally, calve down at 3 - 3.5.

 Monitoring body condition score in late lactation and the dry period to ensure cows don't become too fat and then giving them a gentle transition to the lactating cow ration to ensure maximum intakes should help to ensure you have minimal condition loss when cows are fresh calved. Although it is very important to assess body condition score, the most salient factor to monitor is body condition score change as this shows the severity of any negative energy balance that has occurred.

 

High yielding cows will lose condition quickly when they are milking off their back.  The liver can manage a certain amount of this, but if over one body condition score is lost, that's too much for the liver to manage and insulin production levels will drop, in turn reducing the viability of the egg, which has a knock on effect on conception rates. Feeding a proportion of the lactator's diet through the dry period comes with many benefits, labour being one of them, but critically the diet contains different feed ingredients which keeps the rumen bacteria familiar with these feeds.  This helps to improve post calving dry matter intakes as it reduces the transition from dry cow diet to lactator's ration.

If you are using this system then you need to be aware that it is a more energy dense diet, so it needs to be buffered with straw to reduce the density.   It can sometimes be impossible to feed the necessary amount of straw and the result is that cows are over fed energy as they don't eat the straw made available for them.  Lactator's rations also contain higher levels of calcium, generally either from green forage or a lactating mineral.  This allows the animal to become dependant on calcium supplementation reducing the onset of homeostasis and can result in milk fevers, giving a bad image to what is potentially a very good system.  Just ensure the diet details are thoroughly checked with your nutritionist before putting into action.

Standing hay is becoming more popular, and is essentially a traditional dry cow system on bare pasture with a hay supplement.  The difference is that in standing hay the grass is left to grow very long, well past best quality, to the point where it is largely structural fibre.  This can be a very effective and economical system in which you strip graze the grass until the paddock is at a very low residual (ideally 1500kgDM/Ha) and have some straw available if required.  The critical points are that the grass must be past its best, if it isn't, cows will take in too much calcium and potassium which will inevitably cause milk fever.

Don't allow cows to graze the early re-growth during peak growing condition, as the first leaf is high in potassium and low in magnesium and this again can bring on milk fever problems.  It is also important to ensure that magnesium is supplemented to counter act any effect from high potassium levels, the magnesium is critical in enzyme reactions and will allow the cow to uptake her own calcium reserves.

I also believe it is beneficial to feed up to 2kg dry cow nuts/rolls 2-3 weeks pre-calving. Being on the standing hay acclimatises the rumen to grazed grass which she may well return to after calving, and feeding some corn will begin the rumen working and stimulate the rumen papillae to grow which is where the nutrients are absorbed.  This reduces the nutritional stress at transition when the cow enters the lactating herd.   

Minerals

Balancing minerals is an important aspect of nutritional management. Minerals are essential during the transition period to ensure the animal's own ability to use its calcium and phosphorous reserves post calving. During the far off period animals should be on low levels of calcium intake to train their system to rely on body reserves as opposed to relying on supplementation, this is achieved by limiting good quality green forage. Magnesium can be fed through the whole dry cow period but is essential in the close up period to counteract the effect of potassium levels and enable the cow to uptake her own calcium reserves, this will go a long way to reducing milk fever cases which are often brought on by potassium intakes binding to magnesium particles making it unavailable to the cow, which then prevents enzyme reactions to occur which allow homeostasis. Magnesium chloride flakes fed at 100 - 200 grams/head/day are a good source of magnesium. Dry cow minerals and buckets are also specifically formulated to supply the correct type of magnesium for dry cows. 

 

Trace elements such as copper, iodine and selenium are also important during this period to ensure ezyme reactions are occurring. Vitamin E also works with selenium at this point to help cows' immunity and it can also help with improving cows' cleansings.The DCAB (dietary cation anion balance) system has proved to be very successful on many units, however it isn't for everyone and can make the problem worse if not done correctly.  

Generally, higher yielding animals under greater metabolic stress often require a trigger to help them make the best use of their mineral reserves.  DCAB diets are specifically formulated to balance a set diet based on mineral analyses of the feeds available.  The DCAB product which is a blend of anionic salts will acidify the blood until the diet reaches a DCAB level of -150 to -200. This activates the animal's own homeostasis but also allows the animal to be fed extra calcium and magnesium to fuel the system and trigger an optimal start to the lactation.

Regular pH testing of the urine must be done to ensure the diet is working properly. Partial DCAB diets are becoming more popular as they are simply the inclusion of magnesium chloride at up to 200g/head/day and reducing the feeds which tend to be high in potassium or sodium. This slightly acidifies the blood and supplies a good source of magnesium. High levels of magnesium chloride are bitter to taste so monitor feed intakes closely to ensure cows are not being turned off their feed, either mix the flakes in with the feed or put some in a water trough. Putting flakes in a pierced bag in the water trough often works well.