Energy is key in the transition period

21 July 2020

This is the first in a two-part series on transition cow diets and management, which will cover feeding in relation to energy, and the second will cover feeding to prevent milk fever. 

The term ‘transition period’ refers to the three weeks before calving and three weeks after calving. This provides a crucial, six-week window to ‘set the cow up’ for the forthcoming lactation.

During the transition period, cows undergo many challenges, including hormonal and metabolic changes, compromised immunity, changes in social grouping, dietary changes and loss of appetite – all of which can be stressful. Getting the nutritional management right will help to prepare the cow for calving and minimise the risk of infectious and metabolic diseases in early lactation.

Offering diets with high intake potential and high energy density can achieve higher dry matter intake (DMI). During the transition period, the cow requires energy for the growing calf, producing colostrum and maintaining body condition. Energy requirements for milk production increase rapidly after calving. If the cow’s requirement outpaces her dry matter intake, negative energy balance will result. 

It is important to achieve good rumen fill during the transition period, as this will have a resulting effect on DMI after calving. Ensure the cow eats as much as she can. Including plenty of structural fibre will provide bulk. When the cow calves down, this will support high feed intake, and reduce the likelihood of negative energy balance. Therefore, the larger the rumen volume, the greater possible feed intake.

 

What to do if cows are too thin

Aim to dry cows off at BCS 3.0 to 3.5. If cows are too thin (BCS less than 3.0), the close-up dry cow diet could supply up to 30% more energy than required by adding 3 kg of concentrates. The ideal energy level before calving is 130 MJ/head/day. This should prevent loss of body condition in early lactation, which has a positive effect on health, milk production and fertility. Research has shown that this approach has additional benefits, such as increased immune function post-calving. You may be worried that feeding more concentrates will make cows fat, however research has demonstrated how difficult it is for cows to gain excessive condition during the dry period.

What to do if cows are optimally conditioned

If cows are optimally conditioned (BCS 3.0 to 3.5), the ‘Goldilocks’ approach will supply the exact level of energy required, i.e. ‘not too much, and not too little; just right’. Rations generally combine lower quality silages and chopped straw to achieve a balance of energy (roughly 100 MJ/head/day) and structural fibre. It aims to maintain body condition prior to calving and reduce weight loss in early lactation.

 

What to do if cows are over-conditioned

If cows are over-conditioned (BCS 3.5 or greater), dietary energy should be restricted to less than the cow’s demands. Fat cows will have a lower feed intake after calving and enter a deeper negative energy balance. To compensate for this, the cow will break down her own body fat to use as an energy source, also known as ‘milking off her back’. The products of this fat breakdown are called NEFAs, and if in excess, they are converted to ketones in the liver and ketosis will result. The energy restricted transition diet will prevent this; however, it is important not to starve pregnant cows.

 

In summary, the transition diet is a great opportunity to prepare the cow for lactation. Ensure to maximise dry matter intakes and rumen fill before and after calving. Monitor body condition to determine which approach to energy supply is right for your herd.

 

by Anna Millar, Ruminant Technical Support Coordinator