Doctoral Dissertations

Date of Award

3-1985

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

Henry A. Fribourg

Committee Members

J. B. McLaren, J. H. Reynolds, W. R. Backus

Abstract

A beef-steer (Bos sp.) grazing experiment was conducted on a Typic Hapludalfs soil. The 1.2 ha pastures were (1) Midland (Cynodon dactylon (L.) Pers.) + fescue (Festuca arundinacea Schreb.)(25) + N, (2) Midland + fescue(25) + legumes, (3) Midland + fescue(50) + legumes, (4) fescue + legumes, (5) 1/3 annual grasses + N and 2/3 fescue + legumes in separate pastures (0.4 and 0.8 ha), (6) common (C. dactylon var. dactylon) + fescue(25) + legumes, and (7) orchardgrass (Dactylis glomerata L.) + ladino clover (Trifolium repens L.). Legumes refer to overseedings of ladino clover, red clover (T. pratense L.) and lespedeza (Lespedeza striata (Thunb.) H & A). The 25 and 50 refer to the distances in cm between fescue rows at seeding. Annual grasses were a sorghum-sudangrass hybrid (Sorghum bicolor (L.) Moench) seeded in mid-May and rye (Secale cereale L.)-ryegrass (Lolium multiflorum L.) seeded in early September each year. Annual grass pastures received 134 kg N ha-1 year-1, Midland + fescue(25) + N pastures received 290 kg N ha-1 year-1. Pastures were grazed continuously. Forage growth and consumption were estimated by the cage and strip method. Yearling beef steers weighing 230 kg in the spring grazed 131 to 168 days and were weighed at 21-day intervals. Forage consumption was 62% or more of forage growth, which ranged from 6786 to 14232 kg/ha. Crude protein was well above the minimum requirement for growing steers. Neutral- and acid-detergent fiber ranged from 63 to 67%, and from 39 to 43%, respectively. Stocking rates were between 3.2 and 7.7 steer/ha. Average daily gains (ADG) were greatest on Orchardgrass + clover (869 g/day) and ranged from 478 to 821 g/day for the other treatments. Productivity ranged between 591 animal grazing days/ha for Common + fescue(25.) + legumes and 1537 for Midland + fescue(25), and ranged from 605 to 833 for the other pastures. Daily forage dry matter (DM) intake was 6.3 to 15.3 kg/steer, with conversion efficiencies of about 12 to 20 kg DM/kg gain. Beef production-was 630, 474, 510, 597, 431, 392, and 545 kg/ha for treatments 1-7, respectively. The Species Composition Index (SCI) was evaluated in relation to the-effects of year, season, grazing pressure, forage quality, precipitation, and air temperature on forage growth and consumption, and animal performance. It was compared to the traditional classification variable 'treatment' to describe the seven different pasture combinations. When treatment was entered into the model to explain total variation in forge growth and consumption, ADG, and beef production, R2's of 0.15, 0.32, 0.34, and 0.36 were obtained respectively; when SCI was used, they were 0.36, 0.51, 0.53, and 0.56.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS