Title: Case study: dairies utilizing ultra-high stock density grazing in the northeast Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 2013
Publication Date: February 6, 2013
Citation: Soder, K.J., Hautau, M., Hafla, A.N., Rubano, M.D., Moyer, B., Stout, R.C. 2013. Case study: dairies utilizing ultra-high stock density grazing in the northeast[abstract]. Northeast Pasture Consortium Conference. p 1. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Ultra-high stock density (UHSD) grazing (also loosely referred to as ‘mob grazing’) has attracted a lot of attention and press in the forage industry. Numerous anecdotal articles can be found in trade magazines that promote the perceived benefits of UHSD grazing. However, there is little credible research to support these claims. Additionally, much of the anecdotal information originated from beef herds, in arid climates or areas where cost of production is lower; applicability to temperate climates such as the Northeast is unknown. Grazing dairy managers in the Northeast have expressed interest in UHSD grazing; however, the grazing management and nutrient demands of lactating dairy cows is much different from previously described systems. Furthermore, there seem to be as many definitions for UHSD grazing as there are farms utilizing this type of grazing management. Therefore, a case study was conducted to evaluate the grazing management, animal performance and pasture productivity of grazing dairies that are early adopters of self-defined UHSD grazing. Data was collected on 4 dairy farms in PA and NY during the 2012 grazing season and included: pasture and soil nutrient analyses, stocking densities, botanical composition, and pasture stratification. Data was analyzed using the MIXED procedure of SAS. Means presented are least square means. Farm size ranged from 200 to 620 pasture acres with 60 to 270 lactating cows. All herds were mixed breed with milk yield ranging from 20 to 40 lb/cow/d. Stocking density ranged from 33,750 to 161,111 lb/acre, with an average 39 day rest between grazings. Animals were moved between 1 and 5 times per day, depending on farm management, weather, and available forage. Forage consumed ranged from 50 to 70% of total forage available. Cows consumed the greatest percentage of the canopy cover in the top layers (averaging 75% consumption in the top 8” of growth), with lower layers (0-8”) having less total consumption (averaging 53%). Soil nutrient content for all farms was well within acceptable soil test levels for P, K, Mg and soil pH for perennial cool-season grasses in Pennsylvania. Crude protein (CP) of the forage improved through the grazing season, averaging 20% DM at the Jun./Jul. grazing sessions with a maximum average CP of 28.5% DM during the Sep.-Nov. grazing event. At the same time, neutral detergent fiber (NDF) decreased from an average of 52% to 34% from the Jun./Jul. to the Sep.-Nov. grazing event. The NEL ranged from 0.61 to 0.73 Mcal/lb DM between these two grazings, respectively. These improvements in forage quality later in the grazing season may have been a result of being grazed at a less mature status, possibly due to the first grazing being over-mature due to rapid early-season growth, or due to the forage plants being less mature during each successive grazing. This decreasing plant maturity as the grazing season progressed may have been due to summer slump conditions forcing farmers to return to these paddocks a bit sooner than anticipated to maintain minimum pasture DMI requirements as all farms participating in this study were certified organic. These results indicated that the dairies in this study were following a grazing management system that fell between the traditional management-intensive grazing (MIG) and the traditional definition of UHSD. Traditional proponents of UHSD tend to emphasize soil improvement through trampling high proportions (40-80% of the grass) of very mature material (including seeds, plant fiber and manure) into the soil by putting extremely dense populations of cattle on small paddocks. Long rest periods 60-90+ days) are required between grazings. However, based on the observations of this case study, grazing dairy farmers in the Northeast seem to have taken a slightly different approach to this definition. Rather, they are grazing forages slightly more mature than what has been traditionally recommended in management-intensive grazing systems, and slowing the rotation (30-50 day rotations) to allow these plants to mature, but not nearly as mature as what has been anecdotally reported in ‘mob grazing’ situations. The goal is to increase forage DM available by letting plants grow longer as well as improve the protein to energy balance in the plant to better meet the nutritional needs of the animal.