Maeve Regan discusses the importance of early rumen development in calves and how to aid the transition from pre-ruminant to ruminant.


Newborn calves are born with undeveloped rumens, yet they will spend more of their lives as fully functioning ruminants. The main objective is to assist the transition from pre-ruminant to ruminant by developing the rumen as much as possible before they are weaned off milk, so that they grow to be cost-effective forage consumers that are efficient at converting feed to milk or meat.

Rumen development begins within the first few days after birth and is advanced by exposure to healthy bacteria from the environment and the consumption of solid feeds – concentrates and straw (preferable to hay). Concentrates should be introduced from three days of age (an 18% crude protein calf starter ration/nut ideally) alongside free access to fresh clean water and high-quality clean straw ad-libitum (no haylage or silage).

pre-ruminant to ruminant

Source: Penn State Extension

Considering Weaning 

Weaning on weight basis alone can leave a false sense of security with how ready calves are for the next stage of life/nutrition. The success of the weaning process and the weeks thereafter will hinge on how the rumen has developed over the first weeks of the calf-rearing period. Weaning should never be considered until calves are consuming at least 1.5kg of concentrates/hd/day in grouped pens – signalling that the calves dry matter intake can cope with the transition to a 100% solid feed diet.

Concentrates should be offered ad-lib while on milk but tracked closer to weaning to ensure the group is consuming adequate levels to allow weaning to commence.

Calf Rearing Advice: 

For further advice on calf rearing and calf milk replacer, contact your local Agritech Sales Advisor.


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