PASTURE QUALITY VISUAL ASSESSMENT 0800 BEEFLAMB ( ) INVESTMENT BY NEW ZEALAND SHEEP + BEEF FARMERS

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1 PASTURE QUALITY VISUAL ASSESSMENT 0800 BEEFLAMB ( ) INVESTMENT BY NEW ZEALAND SHEEP + BEEF FARMERS

2 CONTENTS Visual pasture quality assessment 2 When should visual pasture quality assessments be done? 2 What are the assessments? 2 How accurate do the assessments need to be? 2 Visual assessment of a paddock 2 How is each component assessed? 2 Interpreting the assessments with Q-Graze 3 3 Pasture dry matter yield 3 Dead matter 4 Clover and herbs 5 Green grass leaf 5 6 Measuring pasture dry matter yield 6 Sampling for component and quality analysis 7 Calculations 8 Field recording sheets 9 FURTHER READING 400 plus - a guide to improved lamb growth. (Beef + Lamb New Zealand) A guide to feed planning for sheep farmers. (Beef + Lamb New Zealand ) Disclaimer: The information in this publication has been prepared with all reasonable skill and care. Nevertheless, neither AgResearch or Beef + Lamb New Zealand accept any liability, whether direct, indirect or consequential, arising out of the use and interpretation of the information in this publication. Notice of Copyright: AgResearch holds the copyright for the information contained in this publication. Material may not be reproduced without the prior consent of Beef + Lamb New Zealand and AgResearch. This material was developed by AgResearch under contract for Beef + Lamb New Zealand. First published by AgResearch January Redesigned and reprinted by Beef + Lamb New Zealand June

3 VISUAL PASTURE QUALITY ASSESSMENT Visual pasture quality assessment is achieved by observing key pasture features. These features have been used to develop the visual pasture quality assessment protocol and the accompanying software Q-Graze Q-Graze to predict the quality of the pasture, the intake of young growing sheep and cattle, and their liveweight gain. WHEN SHOULD VISUAL PASTURE QUALITY ASSESSMENTS BE DONE? Pasture may be assessed at any time, but visual pasture quality assessment may be most effective during summer when feed quality is particularly important. WHAT ARE THE ASSESSMENTS? The visual assessments are: 1. Pasture dry matter yield, in kg DM/ha to ground level. 2. Dead matter, as a % of the. = dead + clover and herbs + green grass leaf + seedhead and weeds 3. Clover and herbs, as a % of the. = clover and herbs + green grass leaf + seedhead and weeds 4. Green Grass leaf, as a %. = green grass leaf + seedhead and weeds as the remainder. HOW ACCURATE DO THE ASSESSMENTS NEED TO BE? The visual assessments of dead matter, clover and herbs, and grass leaf need to be to the nearest 5%. The pasture dry matter yield assessment to ground level needs to be accurate to approximately 200 kg/ ha because the model converts the visual quality assessments into liveweight gain based on feed eaten. If the feed is not there to be eaten then the outcome will not be accurate. VISUAL ASSESSMENT OF A PADDOCK To make a visual assessment of a paddock, walk 2 that represents the average pasture dry matter yield and quality of the paddock. In hill country, more than one area may be required to represent different slope and aspect combinations. The slope and aspect. Avoid gateways, troughs and camps. Look around and assess the dry matter yield, dead matter, clover percentage and green grass percentage of the sward. Shadows on the pasture can alter your perceptions. Field assessments are recorded and transferred to the computer programme Q-Graze or compared with the feed quality tables in the back of this manual. HOW IS EACH COMPONENT ASSESSED? Please see the Calibration Photographs also provided as part of the Beef + Lamb New Zealand Pasture Quality Workshop. The pasture components are in the following order: PASTURE DRY MATTER YIELD (including any residual that may be left after grazing) in kg DM/ha. that you are using. DEAD MATTER dry matter. of leaves. in summer. 2

4 CLOVER AND HERBS the green material you can see. and plantain. GREEN GRASS LEAF the grass and weed content of the pasture. weeds together. the dead matter. INTERPRETING THE ASSESSMENTS WITH Q-GRAZE Q-Graze is a computer programme that has been designed to incorporate the principles of pasture quality to predict liveweight gains for young sheep and cattle. The Q-Graze programme uses the visual pasture quality assessments to estimate the intake and feeding value of the pasture and then predicts liveweight gains for young growing sheep and cattle. To use Q-Graze, the visual pasture quality assessments are entered along with the pasture dry matter yield, on the input page.the full instructions for Q-Graze are printed in The Pasture Quality Workshops, Principles and Management, and the Q-Graze Manual. Q-Graze users can input paddock sizes and stock details (number, weight, sex, breed) to examine the effects of management decisions such as grazing time on animal growth. PASTURE ASSESSMENT: DEFINITIONS AND BIASES PASTURE DRY MATTER YIELD DEFINITION: Pasture dry matter yield is the dry weight of pasture in kilograms per hectare above ground level. BACKGROUND: Many New Zealand farmers now routinely use visual assessment of pasture dry matter yield. Pastures can usually be successfully ranked from low to high dry matter yield. Q-Graze (the computer model for integrating dry matter yield and quality of pasture to predict intake) requires a total dry matter yield estimate so this measurement must be as accurate as possible. The absolute value assigned to a particular pasture dry matter yield can differ widely between observers, especially in summer and autumn. Historically this has arisen because of a lack of standardisation between training organisations (universities, research organisations, consultants, pasture measurement manufacturers) in the height at which pasture is cut relative to ground level. Calibration must be accurate. Calibration equations on measurement devices and visual assessments must match the season. Local consultants or the manufacturer may be able to help if further information is required. Ideally these tools should be calibrated to your farm each season. Details on how to do calibration cuts are is integrated with dry matter yield assessments it is important to measure actual total dry matter yield. Measurement devices will struggle with pastures with very high dead matters regardless of the calibration chosen. For example, the modern capacitance probes don t measure dry dead material and will give higher readings when pasture is wet than when dry. In these conditions (often dry summer/autumn periods), it may be preferable to rely solely on visual assessments or height measurements (pasture rulers). Pasture rulers give separate calibrations for different seasons for dry matter yield. When visually assessing pasture there are a few common biases: under-. 3

5 ACCURACY: Pasture dry matter yield measurement should be to within 200 kgdm/ha. DEAD MATTER DEFINITION: Dead matter is the percentage of the total dry weight that is dead material, including dead leaf material, dead seedhead as well as dead parts of leaves. BACKGROUND: Dead matter is the main determinant of pasture quality and is the most important component to get right. The dead matter in the pasture is often under. It is normally at the base of the pasture and is out of sight. Initially the observer must open up the pastures to get an appreciation of how much dead matter it contains. Alternatively, the pasture can be cut to ground level and blended. This makes the dead matter more obvious and easy to see. Accuracy is improved by establishing a range over which the dead matter is assessed. Recorded dead matter Most pastures, even well managed pastures, contain high levels of dead matter during dry, warm conditions due to accelerated death rates and accumulated dead matter at the base of the sward. During these conditions, the dead matter will also have a much higher dry matter percentage. AREA SEASON 31 (21-49) 42 (17-76) 23 (7-43) 12 (6-20) 15 (9-23) 20 (15-30) 35 (9-43) 19 (6-38) 11 (2-16) 8 (0-19) 6 (1-13) 19 (6-55) 24 (0-35) 17 (4-44) 36 (11-60) 13 (3-34) 8 (1-23) 14 (3-25) 15 (2-38) 10 (4-20) 16 (2-37) 9 (2-16) 4 (2-8) 8 (2-10) Average dead matter (minimum and maximum) from pastures collected from 4-5 farms per region each month in 1999/2000. Dead matter that has occurred as a result of aging, old dead, in moist conditions has a lower quality than snap dried leaves that have died prematurely due to water stress. This results in different animal performance depending on the conditions. The programme Q-Graze allows a choice of old dead or snap dried. The use of snap dried for the type of dead will depend on the weather conditions and the prevalence of dead matter before the onset of drought. Snap dried is usually reserved for dead matter that was previously fresh green leaf, which has dried off quickly due to drought. The high quality dead matter is normally restricted to eastern parts of New Zealand following sudden dry hot spells. The quality of this type of dead declines rapidly once it rains. ACCURACY: Aim to be within 5% of the actual dead matter content. 4

6 CLOVER AND HERBS DEFINITION: The amount of green clover and herbs as a percentage of green dry weight. BACKGROUND: To simplify the assessment process, herbs such as chicory, plantain and dandelions are included as clover and herbs. The clover and herbs is an important determinant of diet quality, but in most sheep and beef pastures average clover content of sheep and beef pasture as a percentage of total dry matter yield is 10%. clover leaf and stem makes a similar contribution to dry matter yield as a single grass leaf. The easiest way to demonstrate this bias is to assess the pasture, cut and mix the pasture and then visually assess again. The mixing Clover is assessed as a percentage of the green pasture. Ask yourself: What proportion of the green is clover? As pastures increase in height, visual assessors must decrease their assessment of clover because grass weighs proportionately more at higher dry matter yields than clover. Alternatively, very short pastures (<1000 kg DM/ha) contain proportionately more clover and the assessment must increase. ACCURACY: Aim to be within 5% of clover and herbs content. GREEN GRASS LEAF DEFINITION: The amount of grass leaf as a percentage of grass leaf, grass seedhead and weeds. BACKGROUND: Green grass leaf excludes seedhead. Seedhead includes stem with, or which has had (when removed by grazing), emerged) so this is included as leaf. Weeds include thistles, docks and other inedible or unpalatable components of the pasture. The green grass leaf is assessed as a proportion of green grass, for example, 95% leaf with 5% seedhead and weeds. Seedhead is normally present in the sward only from November to February. After this time the seedhead dies and is included in the dead component. Indicative levels of green grass leaf are shown in Table 2. AREA SEASON Jan Mar 97 (92-100) 91 (84-100) 71 (40-96) 85 (76-100) 76 (51-100) 95 (91-100) S (95-100) 87 (62-95) 93 (71-100) 94 (87-100) (98-100) 96 (93-98) 73 (55-83) 62 (37-82) 97 (95-100) 70 (31-100) (94-100) 73 (63-90) 88 (82-100) 91 (76-100) 88 (32-100) Average green grass leaf (minimum and maximum) from pastures collected from 4-5 farms per region each month over 1999/2000. It is important to realise that variation in seedhead during late spring is large and depends on both management paddock must be assessed individually. ACCURACY: Aim to be within 5% of green grass leaf content. 5

7 SAMPLING AND MEASUREMENT PROTOCOLS Calibrating visual pasture quality assessments helps to ensure that results and predictions are accurate. This section provides a basic set of guidelines for those who wish to do their own calibration. Please read all of this section before beginning, as all aspects are related. MEASURING PASTURE DRY MATTER YIELD USING A PLATE OR PROBE ha, a minimum of 40 measurements provides good accuracy when the paddock is relatively even. paddock is patchy. measurement at predetermined intervals, for example, every second step. and conditions. VISUAL ESTIMATES and aspect. assessors each season for greatest accuracy. HEIGHT MEASUREMENTS calibration is used. general calibrations for each season. unit height, while dense pastures are of higher dry matter yield. or cocksfoot, have a low dry matter yield per unit height. also apply to using a ruler. CALIBRATING dry matter yields and pasture type that will be. to high pasture dry matter yield. Browntop versus Italian ryegrass, separate calibrations will be needed for each pasture. 2. Cutting grass assess both pasture components and pasture dry matter yield. material remains and the plant material is cut at the soil surface. hand piece. (commonly m2) is placed over the sward. dirt before weighing. This can be important as small amounts of dirt can contribute a large dry weight. must be dried before working out yields and relative contributions. drying to determine dry matter percentage (see Calculations). composition should be dried at 80ºC for a minimum of 12 hours. dried at 60ºC for 24 hours. moisture so immediate weighing is required. dissections to 0.01 g. kitchen scales are suitable. 6

8 most farm situations. evenly across the microwave plate. microwave and must have water in it at all times 700 W oven). one minute. is recorded, the sample is dry. one minute and repeat the procedure until no weight change is recorded. SAMPLING FOR COMPONENT AND QUALITY ANALYSIS COLLECTING A PASTURE SAMPLE paddock, walk across a representative part (e.g. 100 m diagonal) of the paddock. clippers, electric hand piece or sharpened spoon) three small samples of the pasture to ground level. foot and then a sample midway between each foot. Metabolisable Energy to 0.5 MJME/kgDM. percentage and botanical composition or for sampling for laboratory feed quality analysis. SAMPLE SIZE REQUIREMENTS paddock. is needed to get accurate results from later procedures such as NIR or pasture composition analysis. greater than 100 g (half a bread bag). 100 g is an ideal size. that have been set stocked. into quarters. repeat the process until the required size sample (up to 20 g) remains. completion before taking another small portion. if sample size has been over-. part leaves) and put this into the dead component. protein, and Metabolisable Energy (ME). methods above. until it is cooled, and this uses up the carbohydrate (sugars) in the pasture. as soon as possible for one minute on high in a paper bag or open dish to stop respiration. removal from the microwave. wet grass) when packaged in a zip-locked plastic bag for immediate mailing to the laboratory. drying section) and may be ground before submitting for NIR analysis. 7

9 CALCULATIONS Pasture dry matter yield kg DM/ha = fresh weight of grass (g) x dry matter % Q-Graze 10 * Area quadrat (m2) Dead (%) = dried weight of dead (g) x 100 dried total weight (g) 1 Clover (%) = dried weight of clover and herbs (g) x 100 dried weight of green fractions (g) 2 Green grass leaf (%) = dried weight of green grass leaf (g) x dried weight of grass fractions (g) 3 = dead + clover and herbs + green grass leaf + seedhead and low quality weeds 2 = clover and herbs + green grass leaf + seedhead and low quality weeds 3 = green grass leaf + seedhead and low quality weeds 8

10 FIELD RECORDING SHEET HERBAGE MASS AND COMPONENT ASSESSMENT Name: Mass = kg Dry Matter / ha % dead = dead as a % of total pasture Date: % legume/herb = legume/herb as a % of green pasture % green grass leaf = green grass leaf as a % of remainder Mass 9

11 FIELD RECORDING SHEET HERBAGE MASS AND COMPONENT ASSESSMENT Name: Mass = kg Dry Matter / ha % dead = dead as a % of total pasture Date: % legume/herb = legume/herb as a % of green pasture % green grass leaf = green grass leaf as a % of remainder Mass 10

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14 0800 BEEFLAMB ( ) INVESTMENT BY NEW ZEALAND SHEEP + BEEF FARMERS