Predicting Animal Gains on Pasture Using Cornell Cattle System II

Ed Rayburn1

Cornell Cattle System II was written primarily for use in feedlot situations. The feedlot version can be used with caution for predicting gains of growing beef cattle and dairy heifers. However, two other slightly modified versions are available which are better adapted to prediction animal gains from pasture. These are the Lotus 123 files CCSII-IG.WK1 and CCSII-EG.WK1. The file CCSII-IG is for intensive rotationally grazed pastures while CCSII-EG is for extensive or continuously grazed pastures. These programs have the same screen displays and under lying equations as the feedlot edition of CCSII with a few exceptions. While describing these exceptions, normal feedlot inputs which differ on pasture will be discussed.

Market Description

When describing the market conditions evaluate your in-processing costs to include vaccines and fly control used on pasture. Yardage charges will normally be lower on a pasture system then under feedlot conditions. Change the animal weight, market price table to reflect the weight range of cattle with which you will be working.

Management Description

A code for grazing activity is to be entered to indicate the increase maintenance requirement of animals on pasture. The value entered should range from 0 to 2 with decimal portions allowable. Under intensive rotational grazing a value of 0 to 1 is normal while under continuous grazing a value of 1 to 2 would be more likely. Where adequate internal and external parasite control is maintained the lower values are appropriate. Where management is not provided for these factors the higher value should be used.

Pasture description in CCSII-IG

Average pregrazing forage mass (FM) is the forage standing crop available (lb DM/a) for grazing at the time livestock are turned into a fresh paddock. This can be estimated from clippings or calibrated measuring devises such as height and/or density estimates, plexiglass weight plates, or electronic pasture probes. Under cool humid conditions, good management will keep a FM value between 1000 and 3000 lb/a. Values over 2000 lb/a provide little improvement in animal production. When FM is less than 1000 lb/a animal gains are reduced rapidly.

Daily forage allowance (DFA) is how much forage is provided per day for the grazing herd. This is expressed as multiples of the potential dry matter intake (PDMI) of the herd. If you have 50, 600 lb steers you would expect a PDMI of 750 lb DM/day at a DMI of 2.5% of body weight. A DFA of 2 would mean the herd was allowed 1500 lb DM/day. If the pasture FM is 1500 lb/acre, a 3 acre paddock would provide an average of this DFA over a 3 day grazing period. Values of DFA greater than 1.6 do not improve per head production greatly but do reduce production per acre. Values less than 1.0 reduce production per head.

The values for FM and DFA are used to calculate over 12 periods an estimate of the relative dry matter intake (RDMI) from pasture. This calculation is based on data presented in "Pasture management Facts and Figures for New York", Figure 33. The results from this method are in agreement with intensive rotation grazing studies reported in Figure 34 of "Pasture management Facts and Figures for New York" and other pasture research.

Pasture description in CCSII-EG

Instead of using FM and DFA as under intensive rotational grazing only average forage standing crop (FSC) is used in this version and is entered on the Ration Description page. This estimation should be for the areas being grazed by livestock. If extensive areas of pasture have gone to head or are populated by unpalatable plant species and are not being grazed these areas should not be considered when estimating FSC or forage quality.

Feed additive implant combinations are different on pasture than available under grazing conditions. Under the technology of the 80's this will primarily be only the use of implants. Feed additives currently available give reliable improvement in gains when used in conjunction with grain feeding on pasture.

The FSC value is used to calculate a RDMI for pasture availability based on data presented in "Pasture management Facts and Figures for New York", Figure 33.

References:

Ed Rayburn. 1987. Pasture Management Facts and Figures for New York. Seneca Trail RC&D, 2 Park Square, Franklinville, NY 14737. 92 pp.

1. Extension Specialist, West Virginia University, P.O. Box 6108 Morgantown WV, 26506-6108.

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