1. Types and Nutritional Value of Roughage
Roughage refers to the feed whose crude fiber content in the dry matter of feed is more than or equal to 18%. There are many kinds of roughage which can be used for feeding dairy cows, including hay, straw, greenfeed and silage. Among them, hay refers to Gramineae or leguminous forage, the general moisture content is less than 15%. Common hay roughage includes Northeast Leymus Chinensis, wild hay, alfalfa, etc. Straw refers to straw, vine, and seedling after harvesting of crops, which are divided into dry and green, commonly used are corn stalk, sweet potato seedling, pod, etc. Green feed refers to the grass or leguminous forage and crop plants with more than 45% moisture, such as wild grass, alfalfa, and corn green fodder. Green feed refers to the feed made by cutting, compacting, sealing and fermentation of green feed or crop straw, with a moisture content of 65%-75%.
The nutritive value of different kinds of roughage is also different. For example, the nutritive composition and digestibility of straw are different. The digestibility of crude fiber in Gramineae is higher than that in Leguminosae, while the content of crude protein is just the opposite. The nutritive value of straw mainly depends on the digestibility of fiber, while forage mainly depends on the content of crude protein. Compared with the concentrate of the same weight, the cost of the roughage is low, the volume is large, and the amount of fiber is large, especially the neutral fiber. Because the digestion of the roughage is slow, it is easy to stimulate what is rumination of dairy cows, which is conducive to the survival of microorganisms in the rumen of them and ensures the health of the rumen. The crude protein contained in the roughage is easy to be digested and absorbed, and the roughage also contains various vitamins and minerals needed for the growth and development of dairy cows and lactation.
2. Processing of Roughage
It mainly refers to the physical processing method to change the shape of roughage, which is more conducive to dairy cows' eating. The common methods include mechanical processing, such as chopping, crushing and kneading. The roughage after the above treatment is more conducive to chewing, improving the collection and reducing the waste of feed. But if processed too fine, it will cause a decrease of digestibility, shorten the residence time of feed in the rumen, reduce ruminant activity, decrease the pH value in the rumen, and affect the production performance of dairy cows.
It means that the palatability of roughage is improved by cooking and softening the roughage. Expansion destroys the structure of fibers and increases the digestibility of fibers. However, the equipment required for this technology is expensive and unsuitable for production.
It refers to the natural softening of straw after being chopped and soaked in 1% of saltwater of the same weight for 12-24 hours to improve the palatability and intake of roughage.
There are ammoniation methods, liquid ammonia and urea are used to ammoniate straw under closed conditions to improve digestibility and crude protein level, and to improve the palatability and intake of roughage.
The purpose of treating straw with an alkaline solution of certain concentrations is to destroy cell wall and cellulose structure, release nutrients and increase digestibility and intake.
Through the function of microorganisms and enzymes, the fibers in the roughage can be degraded to produce digestible sugar, lipids, and proteins, which can improve the palatability, digestibility, and the nutritional value of the roughage.
It is a kind of dairy cow feed that has a lactic acid taste and good palatability. It can inhibit or kill harmful microorganisms in the process of fermentation by rubbing and compacting the green feed and then anaerobic fermentation.
It is to dissolve cellulose decomposing enzymes in water and spray them on roughage to improve digestibility, but this method is expensive and not suitable for production.
It is the use of microbial fermentation to degrade lignocellulose in roughage and soften straw. The treated roughage has good palatability, high nutritional value and digestibility, low cost and long storage time.
3. Effect of Roughage on Dairy Cattle Breeding
The structure and function of the rumen of dairy cows determine that a certain amount of crude fibers must be eaten. Roughage can increase the contact area between feed and rumen, increase the volume of the rumen of dairy cows, and make them feel full. Long-term feeding of high-quality roughage can ensure the high and stable yield of dairy cows, promote rumen peristalsis, balance the rumen environment, promote rumination and improve the utilization rate of feed. It can also effectively prevent rumen acidosis. If dairy cows eat too much concentrate feed, many volatile fatty acids will be produced in the rumen, which will reduce the rumen pH value, change the microbial community in the rumen, and produce lactic acid which will lead to acidosis, foot-leaf disease, and other diseases. Therefore, dairy cows feeding roughage can ensure the normal activity of the function of the digestive system.
In the process of dairy cattle breeding, roughage should be taken as the main part of the dairy cow's diet, the concentrate can be used to supplement the nutrition of dairy cows. The rational proportion of roughage and concentrate is the key to ensure the production performance of dairy cows. The quality of roughage can have an important impact on the milk yield of dairy cows. The milk yield of dairy cows depends not only on the proportion of concentrate and roughage but also on the quality of roughage. When dairy cows eat high-quality roughage, their intake often increases. Therefore, when feeding dairy cows, the rational proportion of roughage and concentrate can not only make cows achieve nutritional balance, but also increase milk production.
Feeding roughage can improve the milk fat rate, which is proportional to the rumen acetic acid-propionic acid. The crude fibers in the roughage are decomposed into acetic acid in the rumen. Starch can enhance rumen fermentation and promote the production of propionic acid. Therefore, the proportion of roughage in the diet should be appropriate, when less than 50%, it will lead to the decrease of propionic acid acetate ratio and milk fat content due to the decrease of dietary fiber content. TMR is a good choice for cow training.