Good management through the transition period can minimise metabolic issues and maximise production and reproductive performance.
Massey University associate professor Dr Jenny Weston says poor transition management can result in decreased herd performance and it can be hard to regain that ground lost. One of the key things is setting up the cow for going from a lower level of maintenance feeding to eating at capacity to fulfil the demands when she’s back in the milking shed.
“It’s as if someone’s been on a strict diet for a long period of time and their stomach has shrunk somewhat and you suddenly go ‘Here’s an all you can eat buffet, go for it’. They are less able to cope with eating everything you put in front of them,” Weston says.
However, this doesn’t happen overnight as the rumen needs time to adapt to the dietary changes. Plan to be increasing feeding levels during transition to build their intake back up and consider what is in the diet. Make any changes slowly, the typical rule of thumb is the rumen takes about 14 days to adapt to feed changes.
Ketosis, magnesium deficiency and milk fever round out the big three in metabolic disease of both transition and early lactation cows.
Ketosis
Ketosis is a condition of energy deficit. Cows will always lose some weight post-calving due to a mismatch between feed supplied to meet requirements and what the cow can physically eat. Ketosis is a step beyond this. When fat is broken down the waste products or metabolites – ketone bodies or non-esterified fatty acids – associated with this process are used by the body. When the cow is in a negative energy balance, she will use more fat to provide energy to maintain health and production.
“This excessive breakdown of fat overwhelms the metabolic pathways and causes a backlog of metabolites that accumulate in the blood system,” she says.
Excess ketone bodies in the bloodstream indicate that fat breakdown is occurring at a greater rate than the cow can cope with. Ketosis will usually present as rapid weight loss, reduced milk production, a dry, rough coat and dry manure. Some cows will show off behaviour like aggression, chewing on metal piping and rails, high stepping and a wobbly gait.
Overfat cows and high-producing cows are more susceptible to ketosis as their energy needs are greater. As with most diseases, the number of clinical cases is just the tip of the iceberg. For every one clinical case, there will be around 10 sub-clinical cases. Subclinical ketosis can affect the function of the ovary after calving, which can contribute to non-cycling cows.
Preparing the cow for higher feeding levels and a change in diet composition is critical to preventing ketosis. Attention to detail when it comes to mineral balance is also important along with avoiding having overfat cows at calving and assessing if feed is supplying sufficient energy. The key strategy for treating ketosis is to boost their energy through either oral supplementation with propylene glycol or dextrose given in the vein. A vet may administer an injection of corticosteroid to encourage the cow’s metabolism to boost glucose production. Reducing energy demands, for example, dropping to once-a-day milking can be effective also.
Magnesium deficiency
Cows don’t store enough magnesium (Mg) in the body, so it needs to be supplemented daily. Cows often aren’t efficient at absorbing Mg during times of stress – like drying off, feed shortages and bad weather – and their ability to absorb Mg decreases as they get older.
Clinical symptoms of Mg deficiency will be familiar to most farmers. The uncoordinated stagger of overstimulated muscles is distinctive. Aggressive behaviour, fast heart rate, twitching and, in severe cases, convulsion and down cows can occur. Subclinical symptoms are more subtle – reduced appetite, reduced milk production, kicking cups off and flicking their tail.
“Treatment can be frustrating, so prevention really is critical. Ensuring cows are supplemented with Mg every day is key. The form of Mg will depend on what sort of system each farm has,” he says.
Avoiding feed with high levels of potassium and nitrogen is important as these reduce the absorption of Mg. When it comes to treatment a range of products are around to elevate Mg in the blood, but improvement involves getting enough Mg into the fluid around the brain, which is difficult to achieve.
“It’s hard to predict which ones are going to recover and which ones are going to stay down. Often, they just stand up and walk off after treatment, other times they don’t,” she says.
Milk fever
Milk fever is low blood calcium (Ca). Ca is required for muscle contraction and is stored in the body (in the bones). Ca levels are regulated by the body and when the diet is low in Ca, efficiency of absorption from the gut will increase and the amount lost through excretion will be decreased. It will also be mobilised from the bone during times of high demand, however, this process is not instantaneous and many cows will go down or die before the body has a chance to right itself.
“If you continue to feed high levels of Ca pre-calving, you lull the cow into a false sense of security. Then she calves and starts lactation, Ca demand increases and she can’t keep up,” she says.
Nearly all cows will go into a subclinical phase of low Ca that is considered to be normal immediately post-calving. It’s the cows whose blood Ca drops even further that will progress to clinical cases.
Many symptoms of milk fever are the opposite of Mg Staggers. The early stages are often seen as an odd gait and overly excitable cows. Muscles are affected so cows can’t stand, and this can progress onto not being able to lift their head. The heart muscle becomes weak and it can’t pump as much blood around. The muscles in the gut then stop working, resulting in bloat as the rumen stops moving and gas cannot eructate.
Intravenous milk fever treatments act quickly, but any product that contains Ca or Mg carries a slight risk when being administered into the vein.
“Both can affect muscle contraction and stop the heart, and occasionally a cow dies while treating them. Under the skin treatments are slower to act, especially on a cold day. Typically, I’d advise only severe cases to be treated via the vein, with mild cases it’s best to err on the side of caution,” she says.
Getting enough Ca into a cows system to keep them going for 12-24 hours is important to give the body time to enable Ca mobilisation from bone. Oral treatments are also available but should only be used in mild cases as severe cases affect swallow reflex.
Getting a vet to show everyone on-farm how to give metabolic solutions in the vein is important, as is keeping metabolic solutions in flexi packs on the quad or ute for instant access.
