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The hidden values of providing calves with dry feed alongside milk or milk replacer during the pre-weaning period
Getting the balance right between milk and dry feed during the pre-weaning phase is vital to ensure you produce an animal that can grow and develop their rumen at the same time to avoid any post-weaning checks and ill-health later.

Feeding large volumes of milk for too long during the pre-weaning phase can be detrimental to calf performance post-weaning once the milk feed has been removed. It is fair to say milk is the primary feed for calves during the first three weeks of life or so as their abomasum is their only fully functioning digestive system.
However, early onset of dry feed intake is critical for activating the rumen microbial population and plays a key role in successfully converting the baby calf to a ruminant.
Dry feed is complementary to milk/milk replacer. In fact, the value of dry feed should be put on par with milk and milk replacer because it has such a big role to play in rumen and gut development. By encouraging calves to consume it from the first week of life, the rumen develops, providing a rich source of nutrients for the calf and its microbiome. It also plays a role in recycling the protein used for energy in the calf, reducing the need for this valuable resource to be excreted

In terms of energy, a calf eating 250-300g of dry feed at four weeks of age is consuming the equivalent of 1.5 litres of milk, but the protein produced by the rumen bugs is the equivalent to nearly two litres of skim milk. Not to mention the value of the volatile fatty acids, also produced by the rumen bugs, these are key drivers of calf health too.
The calf also receives plenty of readily available sugar energy from the rumen which is vital in cold weather.
Cumulative intake of calf starter is now seen as a key driver for weaning calves, not the daily dry feed intake over a course of a few days. In the past when calves were fed 600-700g/day of milk powder the two metrics were in sync, but it has been noted that as we increase milk powder intake we reduce cumulative intake thereby delay rumen and gastrointestinal development. When this happens, weaned calves lose condition, as they cannot digest concentrates effectively, and are more prone to pneumonia and coccidiosis.
A recent study was undertaken by (Quigley et al, 2019) to measure the nutrient digestibility in calves fed on different starter and milk programs. The study was to understand the nutrient availability and growth of calves fed moderate to high levels of milk replacer and the composition of fibre and starch in the starter. It was found that the intake of the non-fibre carbohydrate (NFC) which is starch, sugars and other non-fibrous carbohydrate fractions is very important to the young rumen. The fermentation of feed products that produce butyrate and propionate are essential for rumen development, NFC is the most likely feed component to produce butyrate and propionate because it is most rapidly fermented in the young rumen.
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