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United States Department of Agriculture

Agricultural Research Service

Title: Decreasing Forage Allowance Can Force Cattle to Graze Broom Snakeweed (Gutierrezia Sarothrae) As a Potential Biological Control

Authors
item Ralphs, Michael
item Wiedmeier, Randy - USU
item Banks, Jeffrey - USU

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 27, 2007
Publication Date: September 1, 2007
Citation: Ralphs, M.H., Wiedmeier, R.D., Banks, J.E. 2007. Decreasing forage allowance can force cattle to graze broom snakeweed (gutierrezia sarothrae) as a potential biological control. Rangeland Ecology and Management, 60:487-497.

Interpretive Summary: Broom snakeweed is one of the most wide-spread range weeds in the western U.S. If cattle can be forced to graze snakeweed, they may be used as a biological tool to control snakeweed. In the 2004 body condition trial, cows in low body condition (4.6 body condition score, BCS) grazed more snakeweed in the evening grazing period (26% of bites) than the high body condition group (20% of bites). In the 2005 supplement trial, there was no difference in snakeweed consumption between the supplement groups (P = 0.63). Snakeweed was selected only when all other forage was depleted. Cattle grazed 62-95% of snakeweed plants and utilized 50-85% of snakeweed biomass. Cattle can be forced to graze snakeweed by confining them to small areas and limiting alternative forage.

Technical Abstract: Broom snakeweed (Gutierrezia sarothrae (Pursh) Britt. & Rusby) is one of the most wide-spread range weeds in the western U.S. It increases and dominates large areas following disturbances such as overgrazing, fire and drought. If cattle can be forced to graze snakeweed, they may be used as a biological tool to control snakeweed. Grazing trials were conducted in May and August 2004 and 2005 on a crested wheatgrass (Agropyron cristatum L.) seeding that had been invaded by broom snakeweed. Narrow grazing lanes were fenced with temporary electric fence and the cows were moved to a new lane each day. Forage allowance (amount of herbaceous forage available divided by the animal demand) ranged from 24 – 57% of the intake requirement. In the 2004 body condition trial, 7 cows in low body condition (4.6 body condition score, BCS) and 7 in high body condition (6.8 BCS) were grazed in separate lanes. The low body condition group grazed more snakeweed in the evening grazing period (26% of bites than the high body condition group (20% of bites, P = 0.03). In the 2005 supplement trial, one group received a protein / energy supplement high in by-pass amino acids required for detoxification of terpenes (0.54 kg d-1 in the spring and 0.95 kgd-1 in the late summer), while the non-supplemented group received only trace mineral salt. There was no difference in snakeweed consumption between the supplement groups (P = 0.63). The major difference in diets occurred in grazing periods during the day in both years and seasons. Crested wheatgrass and native bunchgrasses were preferentially grazed early in the morning but were depleted by mid-morning and cattle turned to cheatgrass (Bromus tectorum L.). Snakeweed was selected only when all other forage was depleted and averaged 20% of bites in the evening grazing periods. Cattle grazed 62-95% of snakeweed plants and utilized 50 – 85% of snakeweed biomass. Cattle can be forced to graze snaked by confining them to small areas and limiting alternative forage.

Last Modified: 10/24/2014
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