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The 15th International Conference on Silage Highlights

19 August 2009 45,514 views One Comment

Researchers, nutritionists, and agronomists from across the globe met in Madison, Wisconsin from July 27-29 to discuss the most recent research efforts concerning many silage topics. This article will recap the topics most likely to impact farmers in near future.

Session 1: Silage and the Environment

A number of large dairies in California have been recently sued for emitting volatile organic compounds (VOC) from their farms and alleging reducing air quality. When VOC react with nitrous oxides (NOx) they form ozone, which contributes to smog. NOx come from combustion engines. However it is very hard to distinguish how many or which VOC compounds come from nature vs farm operations. Dr. Frank M. Mitloehner of the University of California-Davis, is conducting research to quantify how much and which of VOC are coming from bunker silos with different silage types and face management strategies. Different compounds are emitted from corn, alfalfa, and cereal silages and will eventually have different regulatory requirements.
This is an important topic as the regulations for air emissions from manure storage facilities will be put in place within the next three years in addition to the nutrient management requirements already in place. Regulation of all farm emissions will most likely follow suit, and research like Frank Mitloehner’s will help give farmers options to manage their silage so they can be ready to meet the new regulations. It is true that CAFOs will be under the most stringent regulations, but all farms will need to comply to some degree with the new air quality standards. Many farmers already know this because of the nutrient management requirements tied to water quality at the state, county, and town levels.
Session 2: Silage Additives
The most important thing to remember with the use of silage additives is that they are most effective at making good silage better. Only when these products are added to other good management practices will the use of silage additives result in consistent improvements in silage quality. Dr. Limin Kung, Jr. of the University of Delaware outlined the challenges to effectively using microbial silage inoculants and other additives on farms.
Microbes are very particular about their environmental conditions and a number factors can kill them. Farmers need to pay attention to details if they want to keep the microbes alive. When an inoculant is purchased it should be stored in a cool, dry place and it should be left closed until used in order to keep the microbes alive. Storing the bottle on the pickup dash or open on the workshop bench will kill the microbes. When an inoculant is used the whole container must be used because the microbes will die once they have been exposed after a certain time period. The microbes may also die if chlorine or hydrogen peroxide is present at certain levels in the water used to apply them to the silage. Once the microbes are mixed with water they have certain time frame that they need to be applied to the crop. The water in the tank should also be kept below 95 Fo to ensure microbe survival. An even, well distributed application of the inoculant in the field or at the silo on the silage is essential to give the bacteria a chance to work. The bacteria don’t diffuse throughout the silage, they stay where they are put so it is vital that they be applied uniformly throughout the silage.
Environmental conditions, agronomic practices, and harvest conditions can also influence the effectiveness of microbial silage additives. Putting up silage that is too wet, too dry, waiting overnight to ensile chopped forage, and high temperature fermentation are all conditions that not only reduce silage quality, but they also inhibit microbe growth. Most of the microbes used in inoculants are lactic acid bacteria (LAB). LAB need sugar in order to ferment, and if a silage has lost a lot of it’s sugars due to being rained on, drying down too slow in the field, or being left too long to the field or the wagon then the LAB have nothing to “eat” and won’t help ferment the silage. Additionally some strains of microorganisms will not be able to compete with the microorganisms already present on the silage even if even sugar is present in sufficient amounts. Outside of the farmer’s control is the death of the inoculant from phages. Phages are viruses that attack bacteria. There are no products available to kill phages. Finally different regions of the county have different problems and challenges with making good silage, namely hot humid conditions in the South and West and a periodic lack of complete fermentation in the Midwest.
A number of chemical additives are available on the market to increase the quality of silages. In direct-cut silage systems formic acid is a necessary and very effective additive. However the lion’s share of silages are wilted (field dried) to some degree before ensiling and benefit more from the application of buffered propionic acid, acetic acid, potassium sorbate or sodium benzoate to control undesirable fungi. The application of weaker organic acids is often not effective because yeasts and molds can degrade these acids easily. If a drier silage is being made than higher levels of buffered propionic acid, acetic acid, potassium sorbate or sodium benzoate are required because the number of natural LAB are lower in drier silage. When silage is put up at the optimum moisture content the LAB produce much more lactic acid which suppresses undesirable microbes. Again enough sugar needs to present in the silage in order for the LAB to ferment. The acids can only help the LAB, not replace the LAB.
Bottom line with silage additives: They can help make good silage better, but a large number details need to be paid attention to. Concentrate first on harvesting at the right maturity and moisture content, get the silage put in the silo quickly, and make sure it is packed well. Once a good system of silage making is in place, then adding microbes or chemicals will enhance the system. Generally chemical additives will be more effective than microbes. An even application of either of these types of additives is essential.Come back tomorrow for Part 2 of this series.

Dr Brian Holms of University of Wisconsin-Madison and Dr. Keith Bolsen formerly of Kansas State University outlined the recent changes in order to improve the overall management of silage making. He began by describing a “silage triangle” of people involved in silage making, namely the nutritionist, the agronomist, and the silage harvester. In many situations the farmer himself is one or all of these people, but the principle remains the same-many factors influence how silage is managed. If everyone involved in the process is not on the same page, problems are much more likely to happen. It is very important that these individuals and the farmer meet on a regular basis to discuss how their demands affect the silage making process and come to an agreement for how and when the silage will be harvested, treated, stored, and feed to the animals.

Safety in and around bunker silos is an important issue that can have dire consequences if precautions are not taken. Not overfilling bunkers, properly sloping piles, evenly removing silage from the bunker face, operating at a safe distance away from the bunker face, and many other practices can reduce the risk of injury or death when working in and around silage bunkers.

The increasing rate of harvesting forage has dramatically affected the filling and packing of bunker silos. More often than not the hauling/packing crew cannot keep up with the rate of harvest if the number and weight of packing tractors is not sufficient. Selection of right number of packing tractors with the correct weight is critical is ensure that the silage is packed to a density and porosity that excludes air and enhances proper fermentation. Table 1 outlines the details of this issue. AF=as feed silage-about 65% moisture or 35% dry matter (DM).

 When packing bunkers, the emphasis is shifting toward the porosity, rather than the DM density of the silage. The porosity is the amount of space between each particle of silage, while the DM density is the number of particles per unit area of silage. Porosity is determined by the bulk density (fresh silage density) not DM density. If drier silage is pack the porosity (space) increases, while the DM density remains the same. This space determines how much gases and liquids can flow throughout the bunker. More space = more silage exposed to oxygen = more silage lost. Limiting this space between silage particles will provide more consistent fermentation. Bottom line-Dr.Holmes recommends a minimum bulk density of 705 kg AF/m3 or 44 lb AF/ ft3 and a maximum porosity of 0.40 as a goal when packing forage in bunker silos and drive-over piles. If silage is being packed at 30-40% DM these parameters should be easily met. Silages above 40% DM will need more weight on the tractors to pack the silage to a porosity below 0.40.

A couple of major barriers exist to achieving a bulk density of 44 lb AF/ ft3 and a maximum porosity of 0.40. One is an increasingly common recommendation by nutritionists to put up drier alfalfa silage in order to balance wet corn silage in the ration. Additionally the fields are sometimes mowed and raked faster than the harvesters can keep up which leads to excessive drying in the field to above 40% DM. These are a couple of examples where the members of the “silage triangle” need to sit down and find a solution to improve the quality of silage making. A final consideration when packing bunkers is the type of vehicle used. Many farmers have experimented with using construction vehicles to pack their bunkers. The use of bulldozers, concrete trucks and dump trucks may seem attractive, but farmers must remember these vehicles are not designed to pack bunkers and may have some safety hazards and problems associated with weight distribution. If these vehicles are used, equipping them with tracks can help stability them on the wet surface of the silage. Collapse of bunker sidewalls may occur if the weight of the vehicle greatly exceeds the needs of packing bunkers as well.

Oxygen barrier films are now available on the market to improve the sealing of bunker silos. A layer of plastic that excludes oxygen is placed on the bunker sidewalls and over the top at filling. This layer “sticks” to silage a lot like a Saran wrap does to a kitchen bowl. Then a layer of regular polyvinyl plastic is placed on top. This system virtually eliminates spoilage of the silage compared to a conventional two-layer plastic system. Table 3 below outlines the economics of the feed quality savings vs the cost of the system compared to a conventional two-layer plastic cover.

                                                                                                                                         By Bill Verbeten


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