Veterinary: Rumen development before weaning is key for calf growth

We leaned against the gate, admiring Tommy’s calves.

There was a shine off their coats as they leaped and bucked around the pen. You could see that they were happy and healthy, but most importantly, you could see that they had gained a lot of weight and physique in the last few weeks.

I remembered the conversation that I had with Tommy a few weeks earlier about his feeding regime.

Tommy’s business was one of buying in young calves from a number of trusted sources and rearing them up to store weight.

The most important time in all of this was the early stage of development of the rumen.

A properly developed rumen before the calf reaches the date of weaning means that the calf can handle the transition from a milk based diet to the grass based diet that it will spend the rest of its life on. So how does Tommy do this?

Tommy has a computerised milk feeding system for his calves, which makes it easier for him to regulate the amount of milk his calves are getting.

He feeds his calves at the rate of 15% of their bodyweight per day. He also provides a small amount of a coarse mix calf starter from week, one even though the calves only pick at it in the early stages.

Water is freely available for the calves to drink at all times. He also provides straw, in racks.

I have heard reference in the human sphere that children, if they were allowed to choose what they eat themselves, would end up eating a balanced diet. It is surprising to see how this works with calves.

They constantly pick at the straw, and gradually eat more and more calf starter.

These ingredients end up in the rumen, which is very small in the young calf, but it is the main stomach in the adult animal. The straw and calf starter are fermented by special bacteria here, which need loads of water to function properly.

The fluid content of milk does not do this job, because the milk is diverted into the fourth stomach, the abomasum, where the milk is digested.

When the calf is weaned, it needs to have the rumen fully developed so that it can continue gaining weight by fermenting the grass that it is going to be eating.

If the rumen is not fully developed, then the calf will stop in its growth rate, and “go backwards”.

The coarseness of the calf starter and the scratch factor of the straw help to develop the rumen much faster. Calf starter is the single most important ingredient in the development of the rumen.

I asked Tommy at the start of the season about his milk replacer. He was feeding a 22% crude protein product at the time. Following our discussion, he decided to change to a 26% product with all the protein coming from a dairy source.

As he wanted to have big, thriving calves, he needed to be giving them as much protein as possible, to grow more lean tissue, while also making sure there was sufficient energy provided to make use of this amount of protein.

High growth rates in early calf life make for a healthier calf that will give higher productivity in later life.

In order to achieve these high growth rates the calf needs to be getting at least 23-26% crude protein in the milk replacer.

The conditions Tommy keeps his calves in also help a lot — good, cosy, deep bedding that always seems to be dry.

Animal Health Ireland has a couple of good leaflets online regarding these topics, and of course, your local vet is always a good go-to point of reference.


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