Shortgrass Range Vegetation and Steer Growth Response to Intensive-Early Stocking

Abstract

A 9-year grazing trial was conducted to compare shortgrass vegetation and steer responses under intensive-early stocking (IES) at 2 stocking rates to season-long stocking (SLS). The stocking rates were (1) equal to SLS, with twice as many steers used for the first half of the SLS grazing season (2X-IES), and (2) greater than SLS, with 3 times as many steers used for the same period (3X-IES). The hypothesis tested was that SLS and 2X-IES would be similar and sustainable in terms of productivity and vegetation composition, whereas 3X-IES would be different and not sustainable. The 3 treatments were assigned to 6 pastures in a randomizedcomplete block. Grazing was initiated on or near 1 May each year and continued until about 15 July for IES and about 1 October for SLS. Steers were weighted at initiation of grazing and in mid-July, and SLS steers were weighed in October. Vegetation data were collected in July and October in each pasture from 10 randomly located plots. Species composition of grasses was estimated, and grasses and forbs were clipped separately to determine biomass availability. Steer total gain and average daily gain (ADG) under SLS and 2X-IES were equal (C-0.10) during the early season, but 3X-IES gain and ADG were less (P<O.OS). Total-season gain was greater under SLS (P<O.O5) than either IES treatment, but totalseason ADG was equal to that under 2X-IES. Steer production per ha was equal under SLS and 2X-IES, but greater under 3X-IES (P<O.O5). Western wheatgrass [Pascopyrum smithZ(Rydb.) L&e] and buffalograss (Buchloe dactyloides (Nutt.) Engelm.) composition did not change over time under SLS and 2X-IES, but decreased and increased, respectively, under 3X-IES (P<O.O5). Blue grama (Boutelouugrucilis(HBK.) Lag. ex Steud.) and annual grasses displayed initial composition differences (P<O.lO) among grazing treatments, but not differential composition shifts over time (nO.10). Grass and total biomass availability were reduced (P<O.lO) over time by 3X-IES. The hypothesis was supported: SLS and 2X-IES were equal in terms of both livestock performance and vegetation responses, but livestock performance and biomass availability were reduced and vegetation composition changed under 3X-IES. Thus, 3X-IES was not sustainable. While SLS and 2X-IES appear biologically equal, using them simultaneously on separate land areas may reduce market variability risk by marketing twice per year.

Steer nutritional response to intensive-early stocking on shortgrass rangeland

“…The purposes are to concentrate grazing during the period of highest nutritional quality of the forage, thus increasing livestock production, and to allow a late-season rest so that desirable species enter the dormant season in high vigor. Although this practice is highly successful at increasing livestock production and improving vegetation at up to 3 times the number of cattle recommended for season-long stocking on tallgrass prairie (Owensby et al 1988, McCollum et al 1990), we reported that intensive-early stocking only maintained steer performance and vegetation characteristics at double-stocked-intensive-early stocking, and both responses decreased at triplestocked-intensive-early stocking on shortgrass plains (Olson et al 1993). …”

“…Vavra et al (1973) reported small and inconsistent differences in in vitro dry matter digestibility among grazing intensities, with digestibility being greater under lower grazing intensity when differences existed. Malechek (1984) (Olson et al 1993). …”

“…During the final 2 years of a long-term experiment comparing intensive-early stocking to season-long stocking (Olson et al 1993), we evaluated steer nutritional responses to pasture conditions created by the intensive-early stocking grazing treatments. The objective was to compare dietary nutritional quality and forage intake by steers among season-long stocking, double-stocked-intensive-early stocking, 2.5X-intensive-early stocking, and triple-stocked-intensive-early stocking.…”

Animal and Vegetation Response to Modified Intensive–Early Stocking on Shortgrass Rangeland

“…Pounds of beef produced on a landarea basis is consistently greater for pastures using intensiveearly double-stocking (23 IES), or pastures stocked at twice the season-long density during the first half of the season, than continuous season-long stocked (SLS) pastures on eastern Kansas and Oklahoma tallgrass rangelands (Smith and Owensby 1978;McCollum et al 1990). On shortgrass rangeland in western Kansas, individual animal gain during the early growing season, and total beef production on a landarea basis, is similar between animals stocked at 23 IES and animals stocked at a normal SLS density (Olson et al 1993). Long-term grazing studies have demonstrated that SLS is sustainable at a moderate rate of 2.5-3.0 animal unit months (AUM) ?…”

“…However, vegetative composition or animal gain data revealed that implementing a triple-stocked IES system at 3.45 AUM ? ha 21 (Olson et al 1993), or SLS at 3.85-4.17 AUM ? ha 21 (Launchbaugh 1957(Launchbaugh , 1967 was not sustainable at this site.…”