Effects of a bacterial and enzymatic product on physical and chemical properties of bedding and cow preference in compost-bedded pack barns

Context Compost-bedded pack (CBP) barns are increasingly used to house cows worldwide. They are loose housing facilities where an organic bedding base is mixed daily to remove faeces and urine from the bedding surface and oxygenate the pack, allowing composting to occur. These facilities face challenges in maintaining low moisture percentages within the bedding to ensure cow comfort and good udder health. Aims To investigate current methods of managing CBP barns to maintain compost moisture and temperature at the recommended levels and assess the effectiveness of a bacterial and enzymatic treatment on bedding characteristics and cows’ preference. Methods A 5-week multisite replicated exposure study was conducted on 40 areas of five commercial CBP barns in Australia from late autumn to early spring in 2023 and 2024. The packs were randomly divided into alternating control (n = 20) and treatment (n = 20) areas. All areas were monitored over 1 week to obtain a baseline before the treatment was applied in the 20 treatment areas at the start of Weeks 2 and 4, as per manufacturer recommendations. Compost temperature (°C), area per cow per study area (log m2/cow), and aerial ammonia concentrations (ppm) were assessed as outcome variables every 2 ± 1 day across all five farms. Three farms had additional outcome variables of compost moisture percentage and carbon to nitrogen ratio assessed weekly. Local weather conditions were measured daily, whereas the cultivation rate of the pack (m2/min) was recorded as a covariable for three farms. Multilevel mixed models were used to analyse the effects of treatment, covariables, and the interaction of treatment over time. Key results There was no effect of treatment on bedding conditions. Aerial ammonia concentrations were detected only on 6 days. Reducing the cultivation rate (increasing the time spent per m2) of the pack was effective at increasing compost temperature. Conclusions The product tested was not effective at improving bedding conditions nor did it change cow preference in the packs studied. Management of cultivation rate is important for maintaining bedding conditions. Minimal ammonia detection is a positive finding for human and cattle health in these barns. Implications The product tested needs further evaluation under different bedding conditions if it is to be recommended for use. Australian CBP can be successfully managed to house dairy cows.