Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2013
Publication Date: 2/19/2014
Publication URL: http://handle.nal.usda.gov/10113/58428
Citation: Coblentz, W.K., Brink, G.E., Hoffman, P.C., Esser, N.M., Bertram, M.G. 2014. Fall-grown oat to extend the fall grazing season for replacement dairy heifers. Journal of Dairy Science. 97:1645-1660. Interpretive Summary: Dairy producers in northern climates often want to extend the grazing season or they may need emergency fall forage when it is in short supply due to drought or other conditions. Recent studies have demonstrated that fall-grown oat offers potential to produce a good yield following early-August establishment in central Wisconsin. A 2-year grazing study was conducted with pregnant dairy replacement heifers to assess this forage production technique. Generally, our results confirm that fall-grown oat should be managed as stockpiled forage for deferred (later) grazing. It has little regrowth potential and will eventually winterkill in central Wisconsin; therefore, there is no need to avoid overgrazing, manage plant growth reserves, or develop rotational grazing strategies. Good utilization of fall-oat forage can be accomplished by efficient, one-time removal of standing forage facilitated by a single ‘lead’ wire (electric fence) advanced daily to prevent waste and to allocate forage based on producer management goals and requirements. Generally, concentrations of protein and energy for fall-oat pasture exceeded requirements for dairy heifers weighing 1000 to 1200 lbs. In this study, grazing heifers exhibited comparable performance to heifers maintained on a blended control diet within a confinement management operation. This production system offers an additional effective tool for extending the grazing season into late November within northern climates.
Technical Abstract: Our objective was to assess the pasture productivity and forage characteristics of 2 fall-grown oat (Avena sativa L.) cultivars, specifically for extending the grazing season and reducing reliance on harvested forages by replacement dairy heifers. A total of 160 gravid Holstein heifers (80 heifers/yr) were stratified by weight, and assigned to 1 of 10 identical research pens (8 heifers/pen). Initial BW was 480 ± 43.5 kg in 2011 and 509 ± 39.4 kg in 2012. During both years of the trial, four 1.0-ha pastures were seeded in August to both ‘Ogle’ and ‘ForagePlus’ oat cultivars. Heifer-groups were maintained as units, assigned to specific pastures, and then allowed to graze fall-oat pastures for 6 h daily before returning to the barn, where they were offered a forage-based basal TMR. Two heifer groups were retained in confinement (without grazing) as controls and offered the identical TMR as pasture groups. During 2011, available forage mass increased with strong linear and quadratic effects for both cultivars, peaking at nearly 9 Mg/ha on 31 October. In contrast, forage mass during 2012 remained = 2639 kg/ha on all evaluation dates because of droughty climatic conditions, and it was not affected by evaluation date. During 2012, Ogle exhibited greater forage mass than ForagePlus across all sampling dates (2678 vs. 1856 kg/ha), largely because of its more rapid maturation rate and greater canopy height. Estimates of energy density (TDN) for oat forage ranged from 59.6 to 69.1% during 2011, and narrowly from 68.4 to 70.4% during 2012. For 2011, responses for both cultivars had strong quadratic character, in which the most energy dense forages occurred in mid-November, largely due to accumulation of water-soluble carbohydrates that reached maximum concentrations of 18.2 and 15.1% for ForagePlus and Ogle, respectively. Across the 2-yr trial, ADG for grazing heifer groups tended to be greater than heifers remaining in confinement (0.85 vs. 0.74 kg/d), but both management strategies produced weight gains within reasonable proximity to normal targets for heifers in this weight range. Generally, heifers with no previous grazing experience adapted quickly to grazing fall-grown oat pastures. Fall-grown oat should be managed as stockpiled forage for deferred grazing, and good utilization of fall-oat forage can be accomplished by a one-time removal of standing forage facilitated by a single ‘lead’ wire advanced daily to prevent waste.