Comparison of organic and conventional farming on a grassland farm - 2(nd)Communication: Feed intake, milk yield, health and fertility parameters

In a grassland farm at BAL. Gumpenstein, organic (BE) and conventional farm ing (KE) were compared in an interdisciplinary experiment lasting 11 years. The experimental groups differed in the treatment of slurry (aeration and addition of rock-meal in BE), the level of fertilization (147 kg/ha mineral N in KE in addition to slurry), in the method of weed control (only mechan ical in BE) and the origin of the concentrate for the dairy cows (from orga nic farms in BE, Table 1). Each experimental group comprised 7 Brown Swiss and Holstein Friesian cows until their withdrawal from the group became nec cessary. In that case they were replaced with pregnant heifers or young cow s (Table 2). The feed intake was measured in 12 feeding trials (6 in the su mmer and 6 in the winter period), each lasting 2 to 3 weeks (n = 83 per gro up). At the same time the digestibility of the individual forages was teste d in vivo using 4 wethers each. The milk yield was determined daily for the whole experimental group and also individually for each cow every 42 days by the official milk recording. On a DM basis, the forage ration consisted of 95 % fresh grass and 5 % hay in summer and 56 % grass silage and 44 % hay in winter (Table G). The forag e intake was nearly the same in groups BE and KE (13.4 and 13.1 kg DM per c ow and day, Table 5). In total 1,203 and 1,285 kg concentrate were fed per cow per year in groups BE. and KE, respectively. The OM digestibility of th e forages did not differ significantly between the experimental groups (65. 8 and 64.5 % in hay, 69.3 and 71.8 % in grass silage and 72.2 and 71.4 % in fresh grass in groups BE and KE, Table 3). The milk yield per cow and year was identical (5,867 and 5,877 kg ECM in gr oups BE and KE), however the milk production per unit area was 2,000 kg ECM lower in group BE due to the smaller DM yield of grassland and therefore l ower stocking rate per hectare (7,516 and 9,507 kg ECM in BE and KE, Table 7). There were no significant differences in any of the health parameters (trea tment by the veterinary surgeon, reasons for withdrawal of the cows) betwee n the experimental groups (Table 8). However, there was a slight tendency f or unfavourable values in group BE (e.g. 5.7 and 4.8 treatments by the vete rinarian per lactation as well as 28 and 23 % replacements per lactation in groups BE and KE, respectively). In the fertility parameters, group BE was in part significantly lower (2.3 and 1.9 services per conception in BE and KE, Non Return Rate 29 and 48 %). From the present results it can be concluded that organic farming on a gras sland farm does not lead to differences in the feed value of the forages, f eed intake or milk yield, when compared to conventional farming. However, a lower stocking rate per hectare due to lower DM yield of the grassland has to be taken into account. As a consequence milk production per unit area w ill be reduced.