Transition Milk : The Best Start Doesn't End at Colostrum

Colostrum is a hot topic in calf rearing and rightly so. Feeding 10% of the calf’s bodyweight in high-quality colostrum as quickly as we can ensures the greatest level of Ig absorption. However, the biological role of colostrum extends far beyond the transfer of immunity.

Immunoglobulins are just one piece of the colostrum puzzle – albeit the largest piece, but swapping directly from colostrum to whole milk/milk replacer skips a vital nutritional phase for the calf. There are significant differences in the composition and levels of sugars, proteins, fats, vitamins and minerals in colostrum and mature milk and these variations don’t disappear overnight.

We concentrate a lot on reducing stress around the nutritional changes at weaning and overlook the abrupt transition from colostrum to milk which, in nature, is a much more gradual juncture. This is where we need to be considering a transition milk phase; to ensure we are making better use of the valuable constituents of colostrum that extend beyond the immunoglobulins.

(Conneely et al., 2014)

Oligosaccharides (OS) in milk are receiving more attention due to their bioactive properties as a prebiotic, offering protection against microbial pathogens and promoting the growth of beneficial microflora in the colon. In the first three days of lactation 40 different OS can be identified, whereas in mature milk they are only present in trace amounts. 70% of the OS found in colostrum is sialyllactose (SL) a source of sialic acid which is used in humans to help fight virus.

Immunoglobulins make up around 70% of the protein in colostrum and levels in the milk fall sharply in the first three days. Although the calf’s ability to absorb them ceases at 24h the Igs can still function partially in the gut lumen to control pathogens.

Other functional proteins remain at elevated levels in milk for around one week post-partum. These proteins play roles in the transfer of passive immunity, drive growth, protect against gastro mucosal injury, transport small molecules, offer anti-bacterial protection and modulate the immune system to name but a few.

As we know, fat levels in colostrum are generally higher than in mature milk but the composition of fats also differ, with colostrum containing higher levels of long-chain fats which decrease over a period of five days and a lower level of short-chain fats which increase during the same period. The levels of phospholipids in colostrum are reduced and increase to their normal level from days three to seven post-partum.

The ash content of colostrum is greater; this contributes towards its higher dry matter %. Copper, iron, zinc and manganese are increased 1.7,10.7,10.9 and 3.3-fold respectively. When looking at milk powders we access the level of vitamin E due to the role it plays in supporting the immune system, the vitamin E level in colostrum remains elevated until milking 6.

Introducing five feeds of 50% colostrum/50% milk between the colostrum feeding and milk feeding stages has been found to have the same benefits on gut health and villi length as feeding five extra feeds of colostrum. Mimicking the transition phase in this way allows the calf to receive the additional nutrients intended to overcome the early challenges in life. This could be using whole colostrum, preferably pasteurised, or using a high-quality colostrum replacer, we recommend those containing 100% dried bovine colostrum.