Document Type

Dissertation - Open Access

Award Date

1986

Degree Name

Doctor of Philosophy (PhD)

Department

Animal Science

First Advisor

James K. Lewis

Abstract

Six replications of l-herd 16-subunit High-Performance Short-Duration (HPSDG) and Repeated-Seasonal (RSG) (May-Sep.) grazing system treatments were compared during 1983 and 1984 at the Cottonwood Range and Livestock Research Station located in western South Dakota. Calves and lambs were allotted to the experimental pastures in sets approximately equal on an animal unit basis. Animal numbers were adjusted with put-and-take sets to attain planned forage levels for each cycle of rotation in HPSDG and comparable end of season forage use levels in both treatments. The HPSDG system was operated with four cycles of rotation that had 1, 2, 2 and 3 occupation days and 15, 30, 30 and 45 planned nonuse days during cycles one through four, respectively. Animal performance and production, diet composition and quality, vegetation, standing crop dynamics, forage utilization, soil compaction, and emergence, growth and developmental characteristics of key plant species were studied. Seasonal average daily gains (ADG) of both RSG calves and lambs were greater during 1983 (0.52 vs. 0.39 kg/d and 72.6 vs. 45.4 g/d), and RSG calf ADG was greater during 1984 (0.68 vs. 0.62 kg/d) (PAgropyron smithiiRydb.) and annual grasses and lambs selecting shortgrasses (buffalograss (Buchloe dsctyloides (Nutt.) Engelm.) and blue grama (Boutelous gracilis (H.B.K.) Lag. ex Griffiths)). Distinct changes in standing crop and apparent forage use before and after subunit occupation were quantified in HPSDG as well as at selected dates in RSG. In 1984, peak live plus recent-dead stand1ng crop was observed on August 24 in an ungrazed treatment (2080 kg/ha), July 20 in RSG (1358 kg/ha) and immediately before subunit occupation during cycle 4 in HPSDG (1472 kg/ha). Western wheatgrass and shortgrasses accounted for about 80 to 82% of this peak standing crop in all three treatments. End of season use estimates of western wheatgrass were not different between treatments (P>.05), but use of the two shortgrasses was higher in HPSDG (P.05).

Library of Congress Subject Headings

Grazing
Forage plants
Pastures
Feed utilization efficiency

Format

application/pdf

Publisher

South Dakota State University

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