Partial wilting of grass crops for silage

Abstract

1. During summer 1955 four farm silages were made from wilted grass and clover, silage 1 from bruised material and silages 2, 3 and 4 from long material, all of medium - to low - crude protein content.2. The season was exceptionally warm and dry. The crops were stetmay and when cut contained the low average moisture content of 76.6 per cent. Based on a classification of weather, devised from earlier investigations, meteorological, information showed that weather conditions during ensilage of silo 1 was very good; silo 2, ver oor - ver' :oo silo 3, poor - very poor and silo 4, good - very good. A proportion of silage was, therefore, made under conditions highly favourable towards overheating in the silo.3. It was proposed always to cut one day in advance of filling and to wilt each area for about 24 hours. Due to inexperience with harvesting wilted material more herbage was sometimes cut than could be collected and ensiled in one day so that some of the material was severely wilted. The primary cause of overwilting, however, was faulty machinery which delayed work in the field.4. Results of moisture determinations tended to confirm previous field trials which showed that (a) marked moisture drops occurred in all but very poor weather (b) no advantage was gained by postponing cutting until surface moisture had evaporated and (c) wilted material still lying in the field was not much affected by rain showers.5. Tilted silage made from long herbage, containing: a minimum of overheated and mouldy material can.be produced by making sure that (a) filling is continuous, except during bad weather (b) as much herbage as possible is wilted for periods of up to 24 hours only (c) consolidation is performed continuously, starting with the first layer (d) fillin is carried out rapidly and commenced at the beginning and not at the end of the week (e) no waiting period are allowed for temperature to rise, and a layer of unwilted material ensiled if temperature reaches 120 °11. (48.9 °C.), (f) unwilted herbage is used during the final day's filling and (g) sealing is performed immediately to give a soil depth of at least 9 inches after compression by the tractor.6. Results showed that overheating and moulding is much less likely to occur in wilted material .which has been bruised than in wilted long herbage; It is concluded that for best results some form of mechanical treatment is advisable.7. Chemical analyses of the edible products showed silages 1, 2, 3 and 4 to contain average percentage moisture contents of 70.4, 70.3, 75.2 and 63.7, average percentage crude protein digestibilities of 72.5, 62.0, 73.4 and 68.9, average percentage butyric acid contents in the fresh material of 0.13, 0.01, 0.21 and 0.14, average percentage lactic acid contents of 0.93, 1.31, 1.64 and 0.85, average percentage acetic acid contents of 0.52, 0.23, 0.34 and 0.26 and average pH values of 4.2, 4.2, 4.3 and 4.8.8. Excluding waste and mouldy material preservation was satisfactory in all four silages o but temperatures of up to 130 P. (54.4 o C.) in o silage 2 and 136 o 2. (57.8 C.) in silage 4 caused depressions of crude protein digestibility amounting. to 5 per cent. and 15 per cent. respectively. The depressions were small considering the stemminess of the crop and frequency of overwilting but much greater depressions of protein digestibility would probably have occurred had less consolidation been given.9. Visual inspection showed silages 2 and 4 to,be slightly brown and to possess a slightly sweat odour; characteristics which were not present in silages 1 and 3. The amount of top waste and mouldy material was by far the greater in silage 4 containing the lowest moisture content of 63.7 per cent. The degree of side waste was controlled by type of silo, not by dryness of herbage.10. The silages were fed to Galloway cows, and also to 20 month old heifers and 7 to 9 month old. calves out of blue-grey cows. Silage 3 of highest moisture content, 75.2 per cent., was the least palatable, it being consumed less greedily than the other three silages.11. Finally, while wilted stemmy grass and clover herbage of medium - to low - crude protein content can give a satisfactory silage with a moisture content of 70 per cent., and with relatively small amounts of waste and mouldy m` aerial, it is clear that a depression of about 10 per cent of crude protein digestibility is inevitable unless the crop has been bruised to aid consolidation. Provided all the conditions under point 5 above are adhered to then satisfactory silage can be made from partially wilted herbage in all weather conditions except that classed as 'very poor'. Faced with such an exacting list of rules it is doubtful whether many farmers would seriously consider partial wilting of crops for silage a worth while method.No results are available for farm silages made from wilted leafy herbage but it is thought that the danger of producing overheated and mouldy silage would be less with leafy grass and clover than with stennny material such as that used during the present investigation.