It can be easy for farmers to take their eyes off the ball when balancing their herd’s diet and body condition score (BCS) in the midst of a stressful calving season.
We are now at the latter end of February which means cows have been calving for three to four weeks on many farms, and the BCS of a herd can easily take a hit if negative energy balance (NEB) falls.
NEB can be a particular challenge two weeks post-calving, as the cow begins to pump out more litres while her energy intakes are limited.
When a cow struggles to meet her energy requirements, the extra energy required to match the cow’s milk output will come from her body reserves, and she will start to lose condition.
A cow’s dry matter intake (DMI) post-calving might be around 13-15kg, and will increase by 0.8kg DMI each week for 10 weeks post-calving.
Up until that period, it is quite normal for a cow to be in an energy deficit until they reach a couple of weeks post-calving.
It is crucial at this time of the year, that cows’ BCS is monitored closely for signs of prolonged NEB, which can cause rapid weight loss and lead to cows suffering with ketosis.
While a cow’s intake is limited, it is crucial to try and maximise their DMI through quality feed, while avoiding pinching their diet. Feeding grazed grass, high-quality silage, and concentrates to make up the DMI is favourable at this time of the year.
BCS
To minimise BCS loss and prolonged NEB, the dry cow period has a huge influence as we transition to the milking cow diet.
A successful dry cow diet should result in having a cow calving down with no problems with a BCS of 3–3.25, and for the cow to go back in calf as quickly as possible.
The amount of condition the cow will lose in early lactation has to be kept to a minimum as it will have a significant impact on her milk yield performance for the year ahead.
If a cow loses 0.5 BCS in the first six weeks after calving, this means the cow has lost about 25kg of bodyweight in your typical 600kg Friesian cow, or 4% of her mature body weight, which is substantial.
When assessing a cow’s BCS, key areas to check are the fat cover over the loin, plates, and pin bones of the pelvis and tail areas. You should use your hand for this assessment.
Everyone will score cows differently, but it is important that each farmer’s method of scoring is consistent and that the same person does it each time so each scoring is accurate and reflective of the performance of the herd during the transition period.
Diet
Cows won’t reach their maximum DMI until two to four weeks after peak milk yield. This impact is minimised by feeding the correct proportion of each ingredient and balancing the diet.
Cows can produce a few extra litres of milk from their body reserves which is sometimes referred to as ‘milking off her back’ and it make it difficult to determine how well your diet is working
When we reach six weeks post-calving the farmer will have a fair idea of whether enough energy was provided from the diet or whether the cow was ‘milking off her back’.
It is critically important that silage sampling is carried out as it will make up a fair chunk of the diet on most farms in a spring-calving system. Most silage samples will give an indication of the potential intake of the forage.
The amount of fibre in the forage should be analysed, as it can be the limiting factor when it comes to how much a cow can physically eat. If the silage is not energy-dense enough, cows can end up losing condition.
The protein level of the diet will be a key driver of the milk yield potential and should be driven primarily though grazing when you can this spring.
However, producing more milk and not matching the energy in the diet will affect condition and lead to fertility problems.
As a general rule of thumb, cows should be fed the following amount of concentrates per litre produced each day:
- In full time: 0.33kg of concentrates/litre;
- In by night: 0.22kg of concentrates/litre;
- Out full time: 0.11kg of concentrates/litre.
The priority has to be to increase the cows’ DMI in early lactation as a freshly calved cow will only eat around half of her required intake in the first week post-calving.
Getting grass into the diet and taking grazing opportunities as they come will be a priority on most farms over the next month, with concentrates and protein, in particular, having a huge influence on price received for milk.
However, when getting cows out to grass it is important to get your allocation right through a bit of trial and error and calculating what they need.
Getting the cows out for a few hours is the ideal, but it is important to know exactly how much they have available in the paddock so you can adjust the forage-based diet when they are in by night.
The wet weather over the last few days will have a negative impact on grass utilisation, and DMI will drop 0.4kg for every 1% drop in grass DM under 18%.
Analysing your post-grazing residuals and making sure cows don’t go too tight and poach the land will go a long way towards helping you decide how much supplement is required.
We also need to increase the amount of forage being utilised in the rumen, as it will increase the cow’s energy intake and increase the feed efficiency of her diet.
The transition period is a stressful time for the cow and, so, it is important to be consistent with the cow’s diet and make no drastic changes as stress will lead to drop in performance and condition loss.
