The transition period of a dairy cow falls into a window 3 weeks either side of calving, and it is one of the key timeframes which determines the level of production which can be achieved during her lactation. A dairy cow experiences a severe energy deficit during the first few weeks of lactation, as she simply cannot eat enough to compensate for the energy she’s using producing milk. Consequently, she draws on her body reserves and loses body condition.
There has been much scientific interest as to if and why different feeding regimes during this transition period reduce this energy deficit and improve overall production. One of the questions for which an answer has been sought is whether more milk is produced by improving feeding either before, or after, calving. As always with scientific experiments which deal with livestock, it’s hard to get a clear-cut consensus. Nonetheless, this article has pulled out the main pro’s and con’s of feeding your cows more before or after calving.
When you boil it down, dry cow feeding has two main goals: firstly, it needs to support the growing foetus and udder development, and secondly, it gets the cow ready for the amount she will need to eat once she starts milking. By increasing dry matter intake in the final weeks before calving, it’s believed that a cow can be conditioned for the higher feed intake necessary immediately after calving, which can in turn mean fewer metabolic disorders showing up in the herd. However, while body condition score at calving must be high enough to support maximum milk yield and good cow health, an excessive BCS can be detrimental to production. High BCS cows have lower dry matter intakes after calving, and are more susceptible to metabolic disorders.
Another negative effect of increasing pre-calving feeding levels is the potential that arises for calving difficulties. During the last trimester of pregnancy, a considerable portion of the cows energy intake (including nearly ¾ of protein intake) is going towards the growth of the calf. If cows are overfed to the extent that BCS increases during the last trimester, the result can be a calf which is too big for the cow to give birth to, which when combined with excess deposition of fatty tissues in the birth canal, will greatly increase the likelihood of calving issues occurring.
When it comes to post-calving feeding, it is more efficient for a cow to be producing milk directly from feed energy, rather than by converting feed energy to body reserves and then using body reserves to produce milk. However, cows performing at a high level of production simply cannot eat enough to entirely fuel their early lactation milk production, and so they are forced to utilise their body reserves. But, if a cow is forced to rely too heavily on her body reserves, metabolic disorders such as fatty liver disease can result. There is no clear consensus amongst scientific studies as to the merit of increased pre-calving feeding. As every dairy farmer knows, cows which are overweight at calving are at a higher risk of metabolic disorders and calving issues. Provided that a cow is at an acceptable BCS, the main advantage of increased pre-calving feeding is likely to be in preparing the cow for the feed intake level she will need to achieve once she has calved. On the other hand, it appears that there is no negative effect to letting cows eat as much as they will post-calving. And, perhaps most importantly, across a range of studies, cows that are fed well post-calving have increased milk yields regardless of how they are fed pre-calving, but for positive production effects to be seen from cows that were fed well pre-calving, they also have to be fed well after calving. This summary will probably seem intuitive to most of you. However, that’s good in itself; after all, it is always reassuring when scientific research proves our intuition to be on the right track.