Taking Care of Weaners - Made Easy

November 29, 2021

Are you about to wean this year’s calves?  For many cattle producers, traditional methods involve yard weaning onto hay, but often growth rates in this environment fall below expectations.

Utilising a well-balanced pelleted feed during weaning is becoming a popular alternative, as growers are achieving improved growth rates with this method.  Milne Feeds cattle specialist, Jess Andony, explains how rumen development and performance can be the key to unlocking growth in young stock.  

Cattle producers often ask how weaning onto EasyBeef allows calves to maintain their growth rates. The answer ultimately comes down to an understanding of digestion and rumen development. This allows producers to manage weaning time effectively and set animals up for future production.

When calves are born, their rumen is small and underdeveloped, and they digest food (milk) through their abomasum, which makes up 65-70% of the total volume of the calf’s four stomachs. Milk is channelled to the abomasum, via the oesophageal groove, and bypasses the rumen.

Image 1: Digestive system of a newborn calf. Source: Dairy Australia Rearing Healthy Calves Manual 2020

As calves make the transition from liquid to solid feed, their digestive system begins to change. The rumen, which is designed to handle concentrates, grass and roughage, becomes more dominant and grows as the animal eats more solid food.  At weaning, the rumen should make up 65-70% of the total volume of the four stomachs.

Image 2: Digestive system of a mature cow. Note the size of the rumen in comparison to the abomasum in a mature animal. Source: Dairy Australia Rearing Healthy Calves Manual 2020.

The ability of the rumen to perform well is driven by rumen function and rumen development.

Rumen function refers to the ability of the rumen muscles to operate.  Fibre in the diet is essential for rumen function.  It promotes the growth of the muscular layer of the rumen and helps maintain the rumen lining.  

Long-stem fibre sources, such as hay, are important for rumen function, but the scratch-factor theory for rumen development has been further explored. While long-stem fibre helps to develop the muscle structure in the rumen, it does little to help grow and develop rumen papillae.  Too much fibre in the diet can actually reduce average daily growth rates.

When we look at rumen development, on the other hand, we are talking about the size and number of papillae present in the rumen.  Rumen papillae are finger-like projections that grow from the rumen wall.  Their development is driven by the chemical breakdown of grain and grain-based concentrates.

If calves are to achieve ideal growth rates at weaning, it is essential that they have a properly-developed rumen. The difference between a poorly developed rumen and a well-developed rumen comes down to the number, and size of papillae.  The higher the number of rumen papillae, and the larger in size they are, the greater the surface area in the rumen. This means that there is a larger area available to absorb nutrients from food, which leads to improved nutrient digestion and higher growth rates.  Two key chemicals contribute to papillae development: propionate and butyrate. These volatile fatty acids (VFA’s) are the major by-products of digesting grain and grain-based feeds.  

Image Source: Dairy Australia Rearing Healthy Calves manual 2020, from Penn State University, USA.

The photos above illustrate rumen development on different diets. A diet of milk alone will not result in a well-developed rumen. A diet of milk and hay will lead to some development, but, in order to achieve a well-developed rumen, the addition of grain and grain-based concentrates is necessary.

Rumen development needs to be undertaken in the right way.

The rumen requires a stable environment and dietary changes should be made gradually. If grain is introduced into the diet too quickly, the results may be an over-production of acid, which can reduce the overall pH in the rumen.  Low rumen pH can have an adverse effect, causing papillae growth to slow.  In severe cases, burns may occur and damage the rumen wall. This is commonly seen as sub-clinical or clinical acidosis and causes animals to scour and under-perform.

So, how do you introduce weaners that have just been removed from their mothers to grain-based rations without doing more harm than good?

Jess explains that Milne Feeds pellets contain HyFibe technology, which has been developed to reduce the risk of acidosis and remove the transition period when introducing grain-based feed to ruminants. This takes the worry out of transitioning young cattle onto solid feed, giving producers peace of mind at weaning time.  Weaners can be given access to a Milne pellet, such as EasyBeef, either in a self-feeder or a trough on an ad-lib basis. Providing access to clean water and hay is also essential for yard weaning calves.  Jess mentions that it is important to monitor water intake to ensure all calves are drinking.  It is also crucial to identify any shy-feeders, and separate them from the main group early, to manage the bullying factor and avoid weight loss. A secondary pen to group the shy-feeders in is a good tool to prevent those animals from falling behind.  By putting in place a well-prepared weaner program, producers can maximize their performance and profitability.

Source: https://www.canr.msu.edu/news/rumen-development-of-calves