Abstract
In this study, a number and distribution of dung pats in a grazing paddock and a seasonal change of the area of individual dung pats and dung patches were investigated through the grazing season. Five (LS) or seven (HS) Holstein lactating dairy cows were grazed on about one hectare grass-clover mixed pasture from May to October for two years. Cows grazed 5 hr/day (2.5hr×2) on each paddock under strip grazing management. In each grazing, number and position of dung pats on the paddock were recorded, and also seasonal changes of the area of a dung pat and dung patch were measured through two years. Mean density of dung pats on the pasture was 0.021 and 0.025/m^2 on LS and HS in individual grazing cycles. A distribution pattern of dung pats fitted Poisson distribution (random) on LS. The distribution pattern of dung pats on HS was negative binomial distribution (contiguous), then it became to be a random distribution with progress of grazing. The area of a dung pat gradually decreased through the season, although the dung itself did not disappear at the end of grazing season. Seasonal change of the area of a dung patch was affected by the month of dung dropped and grazing conditions, while the area of a dung patch changed quadraticically in most case. Total area of dung pat was linearly increased on both treatment. Total area of dung pats occupied 1.3-1.5% on the pasture at the end stage of grazing season. Total area of dung patches on the pasture was markedly increased after July and reached maximum level at September on both treatments. The maximum area of dung patches on LS and HS reached about 20 and 11% on the pasture.
