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More Milk from Grass 4 Increasing yield but decreasing feeding value. Feed Unit/Kg DM Digestibility, organic matter 1.1 85 84 1.05 83 1.0 82 0.95 81 80 0.9 79 0.85 78 1,000 2,000 3,000 4,000 5,000 6,000 Yield, kg DM/ha Figure 2. Development in grasses. A number of these parameters can be measured to determine if the forage quality is optimal. Consequently, forage analysis is an important tool for planning cattle feeding. Table 1 is a list of some of the key quality figures. For explanations, see vocabulary page 31. QUALITY PARAMETERS IN GRASSES HEIGHT OF GRASS, CM DIGESTIBILITY ORGANIC MATTER (DOM) % DIGESTIBLE PROTEIN, % CRUDE FIBRE, % NDF, % DIGESTIBLE NDF, % SUGAR, % Pasture grass 6–10 1) 70-80 16–18 < 20 < 40 > 70 Silage 20–30 65-75 14–17 < 27 < 50 > 70 1) 6-8 cm in a continuous stocking system and 6–10 cm in a paddock system. Table 1. Important key figures (content per kg dry matter) for optimal quality of fresh grass or silage. >8 > 3.5 A compromise between yield and feeding value always has to be made for silage. The higher the yield, the lower the quality and feed intake – and vice versa. When producing silage of high quality, an early cut is essential. The grass must be cut before heading takes place. Good and careful silage making is the key to high quality forage and high milk yield per cow. For grazing, the system must be managed well to ensure a “good bite”. The aim is to plan for a high and homogeneous quality (feed value). In a continuous stocking system, the height of grass in general must be kept at 6-8 cm in order to keep an even grass sward - in the spring it is 8 cm and autumn 6 cm. In a paddock system, the aim is to plan for high quality and high feed intake in particular. The grass height must be around 15 cm at the start of grazing and 6-8 cm when cows are moved to the next paddock. To ensure high quality, make sure fresh grass is available at all times. A maximum feed intake in the paddock system is required, and the cows must be
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More Milk from Grass 5 moved regularly. One day in each paddock will ensure the above conditions, and moving the cows twice a day is even better. Three days in each paddock is maximum, but then the feed intake will be lower. The paddock system ensures the highest feed intake and milk yield per cow. The Importance of High Digestibility Several investigations have shown the value of forage with high digestibility – high concentration of energy per kg dry matter. If the digestibility of organic matter or cell walls is improved by 1 unit (%), the intake of forage dry matter will increase by around 0.2 kg DM per cow per day and the milk yield will grow with 0.25 litres or more per cow per day. Figure 3 shows the theoretical production curve for dairy cows fed only on grasses, when milk yield is related to energy concentration in silage. The yield of milk changes from a very high level when using young grass without stems to zero when using old grass of low quality where all energy from the forage is used for the animal’s basic functions. The digestibility is mainly determined by two factors: Composition of the mixture in the field Time of harvest in relation to grass development Kg milk per cow per day Kg milk produced from forage 3300,0 2255,0 2200,0 50% ear emergence, grasses 1155,0 1100,0 55,0 00,0 10.,19 1 01.,91 1,2 01.,83 1,4 01.,75 1,601.6,7 1,801.,59 2 02.,41 2,2 Energy concentration (Feed Units per kg dry matter) Figure 3. Calculation of the expected milk production when filling factors of the grass/silage and capacity of the rumen are used. Source: Danish Agricultural Advisory Service, National Centre. Clover Means Better Forage Clover brings several benefits to a grass mixture: Higher palatability under grazing More even distribution of the annual production in the field Higher feed intake – both under grazing and in silage More protein in the feed
