AgResearch scientist Bob Longhurst reported on the study at the Fertilizer and Lime Research Centre workshop on accurate and efficient use of nutrients on farm nutrient at Massey University in February. He said cows chose not to lie on the pad with no new material as the winter went on, cutting their lying times from about 8.3 hours/day in May to just 1.6 hours/day in June. Conditions on that part of the pad reached a point where cows were removed at the end of June and moved elsewhere for the remainder of the winter.
The area with 12cm replaced also had some reduction in lying time, with recordings going from 10.4 to 8.5 hours/day. Where the pad had 17cm of wood chip applied lying times remained fairly constant at about 10 hours/day.
At Jordan Valley Research Farm in Northland stand-off pads are bedded with 1m of post peelings. The surface layer was also removed and fresh material applied in June, July and August. Cows weren’t confined solely to the pad and had access to grazing.
As the winter went on cows began to increase the time spent on the pad and throughout winter spent only a small amount of lying in the paddock, Longhurst said.
Compacted
The study found that compared with the woodchip pads post peelings broke down more quickly and compacted with stock usage. The particle size decreased and drainage through the pad was impeded, so post peelings had to be replaced more frequently than bark or wood chips.
Coarser materials such as bark and wood chips appeared to have higher nitrogen (N) concentrations. Measures of pad drainage found levels of potassium (K) two to three times higher than those in dairy effluent. K concentrations in pad materials were similar to those of N but if the pad was covered the percentage of K could be twice that of N.
Nutrient levels increased with stock usage. By late winter/early spring faecal bacterial concentrations jumped to be similar to those of dung.
The key recommendations to come out of the study were for farmers to prepare the pad early, preferably in the summer, and have replacement material on hand from the start of the winter so bedding could be replaced as soon as necessary. Using coarser material was preferable if it was available and cost wasn’t prohibitive.
The greater the stocking density the faster the pad deteriorates. And because of the high faecal bacterial levels teat sealing was likely to be advantageous.