Bedding materials for comfortable and healthy calves

Good housing and management of calves is essential for animal welfare, performance in later life and to reduce the risk of disease. Bedding material in the calf barn is an important aspect of calf management.

“Traditional substrates, such as sawdust and wood shavings, can be difficult or expensive for farmers to obtain in some parts of New Zealand, so alternative options are needed that are economically viable, readily available, environmentally sustainable and achieve acceptable standards of welfare,” says AgResearch Scientist Dr Mhairi Sutherland.

“River stones are an alternative bedding material that are already in use by some New Zealand dairy farmers because of cost, availability and perceived improved calf health. This practice came to the attention of the Ministry of Primary Industries and the dairy industry and AgResearch was asked to evaluate the welfare of calves reared on river stones and other bedding materials.”

A number of studies conducted by scientists at AgResearch over the last three years have compared the welfare of calves reared on sawdust (the most traditional bedding material used by New Zealand dairy farmers), river stones and alternative materials.

“In these studies we recorded the body weights, dirtiness, health, skin surface temperature and behaviour of calves during the first six weeks of life,” says Dr Sutherland.

The bedding materials studied included river stones sourced from a river in the South Island (30-120mm in diameter), quarried stones (20 – 40 mm in diameter), pea metal (3 – 5 mm in diameter) sourced from a quarry in the North Island, rubber chips created from recycled car tires (4 – 7 mm) and washed river sand.

“The type of bedding material had no effect on calf body weights, clinical disease or leg health of calves,” says Dr Sutherland.

”Calves remained clean on all bedding materials throughout the six-week study period. However, all bedding materials were maintained using best management practices and were topped up with fresh bedding if needed.

“Some calves reared on stones had areas of hair loss on their knees and hocks at six weeks of age, which was likely caused by the rubbing of the calves’ legs against the hard surface of the stones when they were lying down. This would need to be taken in to consideration if using stones for calf bedding.

“Another important consideration if rearing calves on stones in colder conditions is that calves reared on stones, pea metal and sand had lower skin surface temperatures than calves reared on sawdust or rubber chip, which is likely due to the greater insulation properties of sawdust and rubber.”

There were some important behavioural differences between calves on different rearing substrates. Calves spent less time playing (running, kicking, bucking) on stones compared with sawdust. Furthermore, calves spent less time lying down on stones, pea metal or sand compared with sawdust, with the lowest lying times for calves on stones. Lying times were similar on sawdust and rubber chip. It is important to provide a comfortable surface for calves as they normally spend approximately 70% of their time lying.

The lower skin temperatures along with reduced lying and play performed by calves on stones suggests that calves are less comfortable on stones compared with sawdust.

Finally, the calves’ perspective of stones was determined in a preference test.  Calves showed the lowest preference for lying on stones, strongly favoring every other surface when it was compared with stones in a pair-wise comparison. When calves had access to all surfaces at the same time they showed a very strong preference for lying on sawdust, reinforcing this substrate as ‘gold’ standard for lying surfaces.

Together this work indicates that the choice of calf bedding material is a complex one. While stones perform as well as sawdust in terms of health and productivity, other aspects of welfare such as calf comfort and behaviour are reduced on stones. Sawdust is still the gold standard for calf bedding and alternatives should ideally have similar thermal and comfort properties to maintain equivalent welfare outcomes.