(1) ruminate
There are striated muscles in the esophagus of cattle, which can independently send large pieces of green roughage in the rumen back to the mouth through the esophagus and return to the rumen after re-chewing. This phenomenon is called rumination. Rumination is one of the normal digestive activities of cattle and one of the signs of animal health. Normal rumination of cattle occurs after feeding. Ruminating 6 ~ 10 times a day. 30 ~ 50 minutes each time, the total time is 7 ~ 8 hours, and the reduction or cessation of rumination times is one of the signs of illness.
① Rumination appears and stops.
The fourth stomach (abomasum) is empty, and the rumen wall is mechanically stimulated by large pieces of feed floating on the upper layer of rumen contents. The front part of rumen and omentum contract strongly together, so that the feed at the cardia enters the esophagus. With the cooperation of the reverse contraction of esophageal striated muscles, the feed is returned to the mouth, chewed, and then ground and swallowed back by molars. Cattle chew ruminants about 40 ~ 50 times per bite (under normal diet, chewing times are reduced, which is also a sign of illness). When the front end of rumen and omentum contract together strongly, the feed that has been chewed and fermented at the bottom of omentum also squeezes into the valve stomach through the mesh, and the forage that has been partially absorbed between the valves of the valve stomach squeezes into the fourth stomach. When the fourth stomach is full of forage after ruminating a plurality of food balls, the ruminating action is inhibited and stopped, and a ruminating cycle ends.
② the function of rumination.
When ruminating, the food balls in the rumen will flow back to the mouth. When the food ball is squeezed, the water and small particles in it are swallowed again immediately, while the long particles in the food ball are left in the mouth, and then swallowed after chewing for 50 ~ 60 seconds. Rumination is an important step for ruminants to digest and utilize cellulose normally.
Rumination can increase saliva secretion; It can reduce feed volume and increase feed particle density, which are two important factors that determine the residence time of feed particles in rumen. Rumination helps to separate feed particles according to their size, so that larger particles of feed can stay in rumen for enough time to be completely digested, while small particles are immediately discharged into reticular tissue; Rumination increases the contact area between feed particles and microorganisms, and improves the digestibility of fiber feed.
③ Influencing factors of rumination.
The ruminant activity of cattle is influenced by many factors, such as breed, age, feed quality and environment. Rumination is actually related to the development of rumen. Newborn calves don't ruminate. As they gradually start to eat forage, microorganisms multiply in the rumen and ruminate for a short time within 2 ~ 3 weeks after birth. With the full development of rumen, a normal ruminant cycle appeared.
(2) Rumen fermentation
About 85% nutrients in pasture are digested or modified in rumen. Rumen digestion is completed by rumen microorganisms symbiotic with cattle. More than 90% of cellulose, hemicellulose, pectin and other substances (which cannot be digested by the digestive organs of cattle) are hydrolyzed by cellulase secreted by rumen microorganisms, and the final product is volatile organic acid mainly composed of acetic acid, which is absorbed as a nutritional source of cattle; More than 90% of starch is also degraded by rumen microorganisms, and the final product is also volatile fatty acids. However, the proportion of propionic acid in organic acids produced by starch increased and the proportion of acetic acid decreased.
Rumen fermentation mainly depends on rumen microorganisms in rumen. 1 ml rumen fluid can contain1600-40 billion bacteria and 200,000 species of protozoa. There are many kinds of bacteria and protozoa. The type of food intake determines which bacteria are dominant in rumen, and the group of bacteria determines the production and proportion of volatile fatty acids. Fungi is also a kind of rumen microbial flora.
Rumen environment is most suitable for microbial growth, rumen is anaerobic, pH is 5.5 ~ 7.0, and temperature is 39 ~ 40℃, which is the best condition for various enzyme activities. The food in rumen is generally supplied continuously. The end products of fermentation such as volatile fatty acids and ammonia are absorbed through the rumen wall. The density of microorganisms in tumors and reticular tissues is quite high.
① Main functions of rumen fermentation
Through rumen fermentation, low-quality protein and non-protein nitrogen are transformed into bacterial protein for cattle to synthesize milk protein. Most carbohydrates are fermented to provide energy (the small intestine lacks amylase and can only digest a small amount of starch); Rumen bacteria synthesize B vitamins and vitamin K, and rumen fermentation can also eliminate some toxic components in feed.
However, rumen fermentation can also produce some side effects. The fermentation of carbohydrates in rumen is related to partial energy loss (methane and CO2 production). If bacteria do not have enough energy to convert ammonia into bacterial protein, it will partially degrade protein with high nutritional value in feed and make it lose in the form of ammonia.
Unsaturated fatty acids are oxidized to saturated fatty acids, producing some conjugated fatty acids beneficial to human body. Although rumen microorganisms adapt quickly to the change of dietary composition, it still takes a long time for cattle to adapt to the change of different volatile fatty acid ratios. Therefore, the change of feed ingredients should be gradual (it takes a transition period of 5-7 days). Cattle don't eat bacteria directly. Every day, 2.5 kilograms of bacterial protein (equivalent to 400 grams of nitrogen) can be formed in the tumor and reticular stomach and discharged into the small intestine. These bacteria are digested in the small intestine and serve as the main source of amino acids.
Therefore, to raise cattle well, we must first raise rumen, that is, feed rumen microorganisms well.
② Factors affecting rumen fermentation
A. The content of protein in cattle diet (mainly the content of soluble protein in rumen) is the most important factor affecting the quantity and activity of rumen microorganisms. For example, the crude protein content of pure wheat straw diet is only 3% ~ 4%, which will reduce the number of rumen microorganisms to the normal amount of110, and reduce the ability of cattle to digest crude fiber and starch.
B. Fermentable substances in the diet are the source of energy for the reproduction and digestion of rumen microorganisms, and are also the necessary conditions for the transformation of soluble proteins in rumen into microbial proteins, and for cattle to synthesize microbial proteins by using nitrogen-containing substances such as urea. When soluble sugar, starch and fiber are reasonably matched, microbial efficiency is the highest.
C the diet contains other substances necessary for microorganisms, such as sulfur, cobalt and zinc. Otherwise, the activity and quantity of rumen microorganisms will decrease, and sulfur-containing amino acids and vitamin B 12 cannot be synthesized.
D. when the composition of diet changes, rumen microorganisms also change. However, the change of microbial composition cannot be completed immediately, and it is generally believed that it takes at least 7 days, so the diet is stable, the rumen digestibility is high, and the diet changes greatly. There should be a transition period of not less than 7 days, that is, a small part should be replaced every day, and the replacement should be completed in more than 7 days, which can avoid serious losses such as abnormal rumen digestion and even abdominal distension caused by sudden replacement.
E. Rumen temperature Rumen microorganisms have strict requirements on temperature, and the optimum temperature is 39 ~ 39.5℃. Above or below this temperature, rumen digestibility will decrease. Therefore, we must pay attention to heatstroke prevention in summer and reduce feed (such as corn, sorghum, barley, etc.) that is easy to ferment and produce heat. ), replaced by feed (such as cake, a little oil, etc.) that produces little or no heat by fermentation. ) to avoid high rumen temperature.
F. Rumen pH Rumen acidity is neutral, which is a necessary condition for rumen digestion of roughage. Rumen microorganisms are very sensitive to rumen acidity, and once they are acidic, they lose the ability to digest roughage. Concentrated feed rich in starch and sugar (such as grains, tubers, molasses, etc. ) Rapid fermentation in rumen produces a large amount of acid, which exceeds the speed of acid absorption in rumen and the ability of saliva to neutralize acid, and rumen will be obviously acidic, especially forage with high acid content such as silage, which will make the situation worse. Rumen pH below 6.6 is not conducive to fiber digestion, and below 5.5, lactic acid fermentation is basically the only thing that leads to acidosis. Therefore, when the concentrate feed reaches more than 50% of the diet, 0.5% ~ 1.5% buffer must be added to the concentrate. The better buffer consists of 3 ~ 5 parts of baking soda and 1 part of magnesium oxide.
G. When drinking enough water but lacking water, the water in rumen will be reduced, and it is difficult for forage to turn around and transfer, and it is difficult to ruminate, which will reduce the feed intake of cattle and the circulation of forage in rumen.
H. Bacteria in rumen microorganisms are easy to be killed by bacteriostatic drugs. Use with caution, rumen bacteria are the main participants in rumen digestion. If all of them are killed, rumen digestion cannot be carried out, and all the forage is transferred to the fourth stomach and small intestine for digestion, which is far beyond the possibility of digestion and causes digestive disorders in cattle. Long-term use of antibacterial drugs in cattle will cause extreme emaciation, mastitis, diarrhea and even death.
③ Hiccup
A large number of microorganisms trapped in rumen and omentum strongly ferment various nutrients entering rumen and omentum, producing volatile fatty acids and various gases (mainly methane and carbon dioxide). With the increase of gas in rumen, gas is driven into esophagus, and the process of escaping from mouth is burping. Cows can produce 600 ~ 1200 liters of gas every day and night, 3 times per minute, with a fast frequency of 0.5 ~ 3 hours after feeding, and 0.5 ~ 1.7 liters of gas each time.
Beating, fright, transportation pressure, overwork, etc. Will suppress hiccups. Cattle often eat a lot of tender grass in early spring grazing season without transition period, or eat a lot of leguminous grass with dew in summer and autumn morning, or suddenly feed a lot of fermented feed such as bean curd residue, beet residue, roots, stems, melons and fruits, and feed containing more soluble and viscous protein, which makes the rumen fermentation effect rise sharply, and the gas produced is too late to be released, resulting in rumen gas. It is difficult to burp, and failure to burp will aggravate the increase of rumen internal pressure and form chronic or severe inflation, which will interfere with the feeding and digestion of cattle and cause the death of cattle. Leguminous forage grass is the most prone to abdominal distension, so it is necessary to set a transition period of 7 ~ 10 days when adjusting the diet greatly, and rumen microorganisms can effectively avoid abdominal distension after adaptation.
(3) The function and regulation mechanism of esophageal sulcus.
Ruminants can ingest concentrate such as solid feed, high-quality roughage and calf feed after birth, but in fact, calves mainly rely on milk and milk substitutes to supplement and provide nutrition within 0-30 days after birth. This liquid feed can directly enter the fourth stomach through esophagus without rumination, forming a nutritional intake mode similar to that of monogastric animals.
The contraction mechanism of esophageal sulcus in front of the passage between esophagus and the fourth stomach is a conditioned reflex produced by calf's hearing and vision or hearing and vision to recognize milk and the sound and action of breeder. This is called esophageal groove reflex.
In fact, the esophageal groove can only be completely closed when the calf voluntarily breastfeeds and is in the unique excited state of the lactating calf. The occurrence of this conditioned reflex has nothing to do with the way the calf drinks water (whether it is the liquid from nipple, milk bucket or feeding machine) or the chemical composition of the liquid ingested by the calf (water can also cause the closure of the esophageal groove). On the other hand, if calves are forced to drink liquid or ingest liquid to quench their thirst, their esophageal groove is not closed and the ingested liquid enters the rumen. Generally speaking, when calves are fed with drinking liquid (milk or milk substitute), the closure of esophageal groove is gradually strengthened. For some breeds of calves, when milk jugs, buckets or suckers are used to feed instead of nipples at first, they can still recognize the feeding utensils after stopping feeding for several weeks, and show obvious excitement, which can effectively close the esophageal groove. If regular intensive stimulation is applied, the esophageal groove reflex of most breeds of cattle can remain unchanged for life.
In order to make liquid feed milk and dairy products pass through rumen effectively without entering rumen, careful management of lactating calves is very important.
(1) let the calf remember the method of feeding, so that it can be as excited as sucking milk from a cow's breast; (2) When calves grow and develop to different motives of eating alone, it is necessary to avoid the confusion between the two motives, let calves have free access to drinking water, and limit the amount of milk and milk substitutes, which is helpful to ensure the effective operation of esophageal groove conditioned reflex; At the same time, solid feed (forage and roughage) enters the rumen, thus promoting the development of rumen function and morphology.