Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2013
Publication Date: 3/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59317
Citation: Bohnert, D.W., Sheley, R.L., Falck, S.J., Nyman, A.A. 2014. Knapweed hay as a nutritional supplement for beef cows fed low-quality forage. Rangeland Ecology and Management. 67(2):219-223. DOI: 10.2111/REM-D-13-00091.1. Interpretive Summary: Russian knapweed is a difficult invasive plant to manage and control. One option in a continuing management plan is to use the plant for targeted grazing and even useful as a winter feedstock to supplement livestock fed low quality hay. Russian knapweed hay can be safely used as a nutritional supplement for mature beef cattle consuming low quality forages. This research offers a potential solution to two very serious production problems by lessening the negative impacts of an invasive weed and helping to remove a bottleneck in livestock production systems.
Technical Abstract: Advancing our ability to use invasive plants for producing commodities is central to the agricultural industry. Our objective was to evaluate the potential for using Russian knapweed (Acroptilon repens (L) DC.) as a winter feed supplement for ruminant livestock. Russian knapweed is rhizomatous plant that often grows on accessible and productive land and has protein values similar to alfalfa (Medicago sativa L.). In experiment 1, we utilized three ruminally cannulated Angus × Hereford steers in a completely randomized design to compare the ruminal degradation characteristics of alfalfa and Russian knapweed. In the second experiment, Russian knapweed and alfalfa (13 and 21% CP, respectively; DM basis) were compared as protein supplements using 48 Hereford × Angus, mid-gestation, beef cows (530 ± 5 kg) offered ad libitum hard fescue (Festuca brevipila Tracey) straw (4% CP; DM basis) in an 84-d study. Treatments included an unsupplemented control and alfalfa or Russian knapweed provided on an iso-nitrogenous basis (approximately 0.50 kg CP/d). Cows were stratified by weight and body condition score (BCS) and allotted to treatments in a randomized complete block design using 12 pens (4 cows/pen; 16 cows/treatment). In Experiment 1, the rate and effective degradability of neutral detergent fiber (NDF; 7.3 vs 4.6%/hour; 52 vs 49%) was greater for alfalfa compared with Russian knapweed (P = 0.02). Ruminal lag time for NDF (period before measurable disappearance began) was greater for knapweed (P = 0.03; 3.1 hours vs 1.2 hours). Soluble N (A fraction), rate of N degradation, rumen degradable nitrogen, and effective degradability of N were all greater for alfalfa compared with Russian knapweed (P < 0.01). In Experiment 2, protein supplementation increased (P < 0.01) cow weight gain and BCS compared to the unsupplemented control with no difference between alfalfa and Russian knapweed (P = 0.47). There was no difference (P = 0.60) in the quantity of straw offered between the unsupplemented cows and supplemented groups, but alfalfa fed cows were offered approximately 11% more (P = 0.03) than Russian knapweed fed cows. Total DM offered to cows was greater (P < 0.01) for supplemented compared with unsupplemented cows with no difference noted between alfalfa and Russian knapweed (P = 0.79). Russian knapweed is comparable to alfalfa as a protein supplement for beef cows consuming low-quality forage. Using Russian knapweed as a nutritional supplement can help solve two major production problems; managing an invasive weed and providing a feedstuff that reduces a bottleneck in livestock production systems