In terms of forage supply, silage remains a staple of backgrounding and finishing operations. Silage offers advantages both from an agronomic and a feed perspective. In terms of energy for maintenance and gain, corn silage that receives adequate heat units and is put up under proper conditions is a superior energy source to virtually all forages grown in Canada. Barley silage is also a very good source of energy and protein for growing cattle. In addition to its excellent nutrient content, silage also facilitates feeding management in mixing and delivery and enhanced ration palability.
Putting up quality silage is one of the most important tasks facing feedlot operators at this time of year. Not only is it labour intensive but as the summer heats up, the time window for getting the job done right is short. Since many of you are either on or getting ready to get on the forage harvester, it is worthwhile to examine some of the basic management principles necessary for production of high quality silage.
Whether you are dealing with barley, corn or legumes, focus on cutting at the right stage of maturity, ensiling at optimal dry matter content, cutting to correct particle size, packing to exclude oxygen and covering the pile.
In Western Canada, barley silage is typically cut for silage at the early-to mid-dough stage. When stored in bunker silos, moisture content should be between 60 and 65 per cent. Harvesting at greater than 70 per cent moisture can lead to issues with fermentation, excessive seepage and nutrient loss. Harvesting at less than 60 per cent can lead to issues with packing. In both cases, quality suffers. Corn typically is ensiled at 65 to 70 per cent moisture. Corn moisture content can be monitored by following milk line development after denting. Values of one-half to two-thirds milk line are commonly used as targets for optimal maturity. However, depending on the conditions and variety, these values may not correspond to optimal moisture content for harvest. Actual monitoring of moisture is recommended to ensure the correct stage of maturity for cutting. For beef operations, alfalfa is best cut at five to 10 per cent bloom. Wilting may be necessary to achieve a desirable moisture level (68 to 70 per cent).
Ensiling at the proper state of maturity, particularly for cereals such as barley and corn ensures an adequate level of water soluble carbohydrates in the plant material. These carbohydrates are used by bacteria naturally found on the plant to produce lactic acid is necessary for rapid pH decline and preserving as much dry matter and nutrient content of the original plant material as possible. Excellent-quality silage has a pH value of 3.5 to 4.2 while greater than 4.5 indicate a less-than-desirable fermentation. One of the difficulties with putting up good-quality alfalfa silage is its low water soluble carbohydrate content and its inherent high buffering capacity. These factors make it difficult to reach a desirable pH value with alfalfa silage.
Particle size is a function of your forage harvester and its operation. Particle size of cut forage can be controlled by adjusting feedroll speed and by adding or removing knives on the cutter-head. Slower feed rates and/or more knives result in a shorter cut length. Theoretical cut lengths of 3/8 inch for barley and alfalfa and up to 3/4 inch for corn (depending on use of a kernel processor) are considered desirable. Silage cut too long is difficult to pack; too short is not efficient.
Packing is critical to eliminate as much oxygen from the silage pack as possible. Too much oxygen can lead to an undesirable fermentation, mould growth and in some cases heat-damaged protein. The key to eliminating oxygen is packing, packing and more packing! Once the bunker is filled, the final step is covering the silage with an appropriate silage-grade plastic cover. Covering helps to keep oxygen from penetrating into the top layer of the silage, as well as prevent environmental damage. Properly covered silage will have significantly reduced dry matter and nutrient losses, particularly in the upper three feet of the pack.
One question that often comes up is “should I use an inoculant or preservative?” There is no simple answer to this question as there are a host of factors influencing the response to these additives. In the case where corn or barley silage is put up properly, it is doubtful that silage inoculants will be of any great value. If conditions are less that optimal at ensiling, then the use of an inoculant may be justified as research has shown enhanced dry matter content, lower silage pH and in some cases improved animal performance when such products are used. When dealing with grass or legume silage, it is easier to make a positive argument for the use of inoculants and preservatives. In such cases, it is a good idea to do your homework to ensure you are selecting the right product for the crop you are ensiling.
JohnMcKinnon isabeefcattle nutritionistat theUniversityof Saskatchewan