[MUSIC] Hello, my name is Alex Hristov, and I am Professor of Dairy Nutrition at Penn State University. This lecture will talk about feed processing and its importance in feeding dairy cows. So why are we discussing processing of feeds? The answer to this question is simple. Because we want the cow to get as much energy and other nutrients out of the feed we offer to her as possible. It is important to remember that by processing, most of the time we increase the energy value of feeds. Other reasons for processing include improved palatability, the reduced feed losses and better feed preservation. With forages, we reduce the particle size by chopping the plant material so the microbes in the rumen can access the digestible nutrients. Microbial digestion cannot take place unless the microbes attach to the plant particles. They have to literally colonize the plant fragment to start the digestion process. In nature, the cow will have to chew the roughage she consumes to allow access of the rumen microbes to the plant tissues. We help ruminants by doing some of the work by chopping forages for them. They still chew their cud, which is very important for producing enough saliva to buffer the rumen, but processing decreases the energy expended for particle size reduction. Keep in mind that a healthy cow with a normal dairy diet produces around 25 to 50 gallons, or 98 to 190 liters, of saliva everyday. Particle size is very important for proper rumen function. Penn State has produced the particle separator that is a simple device with several sieves allowing evaluation of feed particle size. The forage or ration sample is shaken for several minutes and then the proportion of particles left on each sieve is weighed. This table shows recommended particle size distribution for a dairy total mixed ration and corn silage and alfalfa haylage samples. Briefly, the top sieve will retain particles that are larger than 0.75 inch or 19 millimeters, and are likely to promote chewing and salivation. As particle size decreases from larger than 19 millimeters to smaller than 4 millimeters, which is around 0.16 inch, their chance to leave the rumen increases and their function in promoting saliva production decreases. Particle size distribution guidelines for corn silage, alfalfa silage, and total mix ration and instructions how to use the Penn State particle separator can be found in the additional readings for this lecture. Wet or dry forages should be chopped to promote microbial colonization and digestion. The particle size guidelines outlined above and in the earlier silage lecture should be followed. It is important then the forage is not chopped too fine, because this will lead to lack of effective fiber in the diet and may contribute to rumen acidosis. Dr. Dave Mertons from the Dairy Forage Center in Madison, Wisconsin, defined effective fiber, or eNDF, as the overall effectiveness of the neutral detergent fiber in the diet for maintaining milk fat test, and physically effective fiber, or peNDF, as the specific effectiveness of neutral detergent fiber for stimulating chewing activity. Mertons calculated, for example, that physical effective fiber of soybean hulls, brewers grains, corn silage, legume silage fine chopped or legume silage coarse chopped, legume hay, and grass hay were 3%, 18%, 81%, 67%, 82%, 92%, and 98%, respectively. What is important to remember here is that by-product feeds, such as soy hulls, for example, may have high fiber content, 60% neutral detergent fiber. But their effective fiber will be very low, only 3% compared with over 90% for hay, because of their low ability to promote chewing and saliva production. There are other treatments that can be applied to low-quality roughages such as straw or corn stover. These include treating the forage with alkali, anhydrous ammonia, or urea. These treatments are intended to partially break down bonds between digestible fiber and indigestible lignin, thus increasing the overall digestibility of the feed. Additional benefit with ammonia or urea, which will release ammonia when hydrolyzed during the treatment process, is that the crude protein content of the forage will also increase. This can be particularly beneficial with low-quality hays, straw, corn stover or other high-fiber by-products. The effect of anhydrous ammonia can be substantially enhanced if ammonia is used under pressure and increased temperature. Installations such as the one shown here combine liquid ammonia, pressure, and high temperature to achieve up to 15% increase in wheat or barley straw digestibility. Anhydrous ammonia can also be injected into bales covered with plastic, as shown in this picture. Next we will talk about processing grain. If not chewed by the cow or somehow processed before being fed, grain kernels can remain indigested in the rumen for a long time due to the protective function of their seed coat or the pericarp. Therefore, to facilitate digestion, the seed coat of the grain kernel has to be at least damaged so the microbes can penetrate and digest nutrients within the kernel. For some grains that are less digestible, such as corn, for example, the extent of processing is directly proportional to the extent and rate of digestion in the rumen. The effect of processing on digestibility of grains such as barley and wheat is small due to their inherently higher starch and protein digestibility than that of corn and sorghum. This means we can, to some extent, regulate digestion rate of grain, particularly starch, by processing. For example, if we would like to have a more rapid rate of corn starch digestion, we would use a more aggressive processing such as fine grinding, steam rolling, or steam flaking. If our diet already contains a lot of digestible carbohydrates and we would like to minimize corn starch digestion rate but still not lose starch in manure, we would use a less extensive processing method such as coarse grinding for example. We have to always keep in mind that fine-grinding grain will increase its digestibility for dairy cows but, depending on the overall diet, may also increase the risk of acidosis. There are two types of grain processing, physical and thermal, or heating. Physical processing is used to break the seed coat and allow microbial access in digestion. This kind of processing may also increase palatability of the grain. Usually the advantage of physical processing is with small, hard grains and for grains with thick seed coat. Thermal processing involves temperature and usually also moisture. Starch is heated, grain swells and gelatinizes. The advantage of thermal processing is with less fermentable grains such as corn and sorghum. There are also other methods of processing such as roasting, pelleting, extrusion, and micronization. Thermal processing called heating usually involves steam. The time of exposure to heat or steam will determine the extent of starch gelatinization and its digestibility. Steam-rolling, for example, exposes the grain to steam for up to around eight minutes, and starch gelatinization is kept to a minimum. With steam-flaking, on the other hand, grain is exposed to steam up to 30 minutes and starch is gelatinized to a much greater extent. Then the grain is rolled into flakes of varying thickness, which is also called test weight, depending on the type of animal it's going to be fed to. Gelatinization is proportionally related to digestibility because the combination of moisture and heat break down the intermolecular bounds of the starch molecules. The starch granules absorb water, swell, and then burst, releasing starch. Steam-flaking is perhaps the most extreme process of grain that has the greatest effect on starch digestibility. The decision to use one grain processing method over another, however, has to be also based on cost of processing. Processes such as steam-flaking are more expensive and may not be justified under some conditions. For example, with grains such as barley, or when the diet already contains high levels of digestible starch or corn silage with high proportion of grain harvested with a kernel processor. Tempering is another grain processing method consisting of adding water to the grain and allowing to soak for up to 24 hours. This causes some swelling of the starch and increases digestibility. In some cases a tempering agent is added. These are surfactants, usually saponin-containing products, which facilitates water penetration into the kernel. The grain can then be rolled to different thickness depending on whether it's going to be fed to beef or dairy cattle. In our previous lectures, we discussed roasting of whole soybeans and extruded soybean meal. Both products are good sources of rumen bypass or rumen-undegraded protein, and also provide extra energy as fat to the cow. On this last point, the two feeds are quite different. Whole soybeans have up to 19% fat and extruded soybean meal up to 10% fat. More importantly, whole soybeans are less likely to affect fermentation in the rumen because fat is released at a slower rate than fat from extruded soybean meal. You may remember that unsaturated fatty acids such as those found in soybean and other vegetable oils are more detrimental to the rumen microbes than saturated fatty acids predominant in animal fat. Whole soybeans are usually roasted to around 270, 320 degrees Fahrenheit, which is 130 to 160 degrees Celsius. This is intended internal grain temperature, and then further processed before being fed. Fine grinding will increase protein degradability and is therefore not recommended for roasted soybeans. It is usually recommended that they are coarsely processed to halves and quarters. There are different systems used to roast beans, such as drum roasters, high-temperature air dryers, or open-flame roasters. Independently of the process, temperature and heating and steeping time have to be monitored to achieve desirable rumen bypass protein levels, but also not overheat the beans. The later may cause formation of indigestible [INAUDIBLE] products, which will decrease intestinal digestibility of the soybean proteins. Roasted corn or other grains such as barley and wheat can also be fed to dairy cows. Heating of the starch increases gelatinization and digestibility. Roasting also produces caramelization of the sugars in the grain, which enhances palatability and may increase feed intake. Last we will briefly discuss extruded soybean meal. A number of commercial extruded, expeller soybean meal products are available on the market in the US. The processes used to produce these meals vary, but are generally based on the principle of pressing the beans with a screw press which partially extracts the oil and creates heat by friction. In the extrusion process, beans are first preheated in a dryer, which prepares them for the higher temperature of the extruder. This higher temperature cannot be reached if the beans are not preheated, then moved to a receiver, and finally pressed through a discharging die by high roast screw in the extruder. Temperature is usually around 300, 320 degrees Fahrenheit, or 150 to 160 degrees Celsius, and is regulated by adjusting the pressure through the die, which increases or decreases the friction and the temperature of the extruded beans. This is the end of today's lecture. In our next several lectures, we'll discuss specifics of feeding lactating cows at the various stages of their lactation cycle. [MUSIC]
