Pre-Weaned Calf Rearing on Northern Irish Dairy Farms: Part 3-The Impact of Environmental Factors on Calf Performance.

Nutrition, healthcare and management of the rearing environment all interact and have an impact on the performance and feed efficiency of pre-weaned dairy calves. In a survey of 54 dairy farms in Northern Ireland, average daily gain (ADG) of 369 pre-weaned calves was assessed. Dietary and nutritional information detailing intake of milk or calf milk replacer (CMR) and the composition of milk/CMR and solid feed diets was collected. Environmental and hygiene-related parameters within calf rearing facilities were recorded. It was hypothesised that suboptimal environmental management conditions would negatively affect calf performance and cause the observed average daily gain and retained energy to fall below values predicted from nutritional intake alone. Factors that tended to be negatively associated with the observed calf ADG were increased time (>50%) below lower critical temperature (LCT), increased time (>10%) above 0.4 m/s airspeed and reduced straw dry matter (<70%). Potential calf ADG was predicted using the young calf model from the Nutrient Requirements of Dairy Cattle (8th Edition). The predicted and observed calf ADG and retained energy (RE) were compared to assess whether the individual observed calf ADG was greater, equal to or less than that predicted by the model. Environmental factors associated with calf ADG or RE being less than the model prediction included: greater than 30 animals housed in the calf house, increased time (>10%) above 0.4 m/s airspeed and where coliforms were detected in ≤50% of milk samples on that farm. These results demonstrate the relevance of management of the rearing environment in optimising pre-weaned calf performance and feed efficiency.