Submitted to: International Grasslands Congress
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2005
Publication Date: 7/20/2005
Citation: Soder, K.J., Sanderson, M.A., Stack, J.L., Muller, L.D. 2005. Intake and milk production of lactating dairy cows grazing diverse forage mixtures over two grazing seasons[abstract]. In Murphy, J. J. (ed. Utilization of grazed grass in temperate animal systems, Proceedings of a satellite workshop of the XXth International Grasslands Congress. p. 164. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Voluntary intake and stocking rate are key determinants of animal performance on pasture. Greater plant diversity in grassland plant communities has been linked to increased primary production, greater stability in response to disturbance, and reduced weed pressure. Thus, increasing plant diversity may be one approach to improving animal productivity. An experiment was conducted to determine the effects of forage diversity on intake and milk production of lactating dairy cows over two grazing seasons. Four diverse forage mixtures were established in replicated 1-ha pastures at University Park, Pennsylvania, USA in the autumn of 2001: 1) orchardgrass (Dactylis glomerata L.)-white clover (Trifolium repens L.); 2) orchardgrass, white clover, chicory (Cichorium intybus L.); 3) orchardgrass, tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and chicory; and 4) six species plus white clover, alfalfa (Medicago sativa L.), and bluegrass (Poa pratensis L.). The experimental design was a randomized complete block with two replicates. The pastures were subdivided into smaller paddocks and stocked rotationally with lactating Holstein cows during April to August in 2002 and 2003. Four cows grazed each treatment. Herbage allowance was 25 kg dry matter/cow per day. Cows were fed a 13% crude protein corn-based concentrate (1 kg/4 kg milk daily) in two equal feedings after milking. Cows were moved to a fresh paddock after morning and afternoon milking. Herbage intake was estimated by the chromic oxide technique during May, June, July, and August in each year. Daily milk yield and weekly milk composition samples were collected. Pasture quality was on the high side but within the range summarized by other regional studies. A significant year effect was noted for most nutrients with greater differences noted during 2002 (a drought year). Pasture DM intake was not affected by pasture diversity treatment; however, there was a significant year effect. Milk yield, milk fat, and milk protein were not affected by pasture diversity treatment or year. Milk urea nitrogen was significantly affected by year. Managing for a moderately complex mixture of forages on pasture may result in greater carrying capacity of the pastures due to increased forage productivity and reduced weed competition, while maintaining animal productivity. Despite large shifts in species composition, proper grazing management (particularly herbage allowance) and strategic supplementation can buffer changes in milk production.