How important is curding for digestion of milk proteins?

What if I told you that approximately 25% of calves don’t produce a curd, even when fed a curding milk replacer.

Article supplied by Natalie Chrystal, Nutrition Consultant to AgriVantage

Optimising the management and nutrition of calves on dairy farms is essential to the long-term productivity of every dairy herd. Realising the importance of calf nutrition, researchers around the world have invested substantial resources into understanding preruminant calf physiology.

Over the last 100 years there have been some dramatic leaps in our knowledge of the digestive systems of the young ruminant and our understanding of the impact of nutrition on the lifetime productivity of the young animal.

How important is curding for digestion of milk proteins

The importance of the role of curd formation in the digestion of milk by the young calf has been an area of debate for decades.

Over twenty years ago, Longenbach and Heinrichs (1997) published a comprehensive review of the importance and physiological role of curd formation.

They noted that despite extensive research up until that point, “the complete function and necessity of abomasal coagulation in calves, beyond colostrum feeding, remains questionable with current feed processing technology”.

They further noted that “most criticism has been directed towards the use of non-casein based milk replacers based on tests and studies designed for milk/casein based replacers” and concluded that future assessments of the suitability of milk replacers should be based on overall calf performance and not solely on the curding properties of the replacer.

More recently, in 2009 and 2010, Japanese researchers published some innovative research work which has helped us to get a better understanding on the importance of curd formation in young calves.

These researchers (Miyazaki et al., 2009), in an effort to develop a suitable method for the real-time assessment of curd formation in young calves, assessed the suitability of ultrasonography for this purpose.

They included both curding (ie casein-based) and non-curding (ie whey-based) milk replacers in their assessment and confirmed the ability of the milk replacer to form a curd prior to feeding the milk replacer to the calves, using an in vitro rennet coagulation test.

Calves were fed milk replacer twice a day and were assessed using ultrasound at varying time intervals.

While the authors concluded that the use of ultrasound could be a suitable means of assessing curd formation, they also unexpectedly found that no abomasal curd formed in one of the six calves fed the curding milk replacer.

They then carried out a second study to assess abomasal curd formation in 29 preruminant calves fed a curding (casein-based) milk replacer. Once again, the researchers confirmed the curding properties of the milk replacer in the laboratory. Calves were fed milk replacer twice a day and were assessed 2 hours after feeding. In 21 out of the 29 calves, there was clear formation of a curd. However, in 8 of the calves, presence of a curd could not be determined.

These calves were assessed again multiple times until 7 hours post feeding, with no change in outcome.  All of the calves, except one of the non-curd forming calves, were considered healthy, and the researchers considered that there was no apparent difference in appearance, appetite or vigour between the 21 curd forming and 7 healthy non-curd forming calves.

Taking account of this novel and current research and looking back at some of the research published over the last 100 years, with a better understanding of the calf development and the digestion of milk, it is becoming increasingly clear that curd formation plays an important physiological role in the success of passive transfer of immunoglobulins in colostrum in the first 24 hours of life, but not in the digestion of milk proteins.