A Canadian yellow flower taller than a human was uprooted, cut off, loaded into a car, and sent to a sheep farm in Lianshan Village, Daixi Town, Huzhou City, Zhejiang Province. There, it is crushed into forage by a guillotine kneading machine, and the Canadian goldenrod becomes fodder for lake sheep.
Xiang Jizhong, the head of the farm, ate it a year ago when he first tried to put a Canadian yellow flower in front of the lake sheep, "beyond my imagination." In October 2022, Xiang Jizhong began to feed sheep on a large scale of Canadian goldenrod on a sheep farm, and the farm of more than 2,700 sheep can consume about 6 tons a day.
In the past, few people equated Canadian goldenrod with animal feed. In 2010, the former Ministry of Environmental Protection was included in the List of Invasive Alien Species in China (the second batch) and in the List of Invasive Alien Species under National Key Management (First Batch) by the former Ministry of Agriculture in 2013. Like many invasive alien species, it can harm local biodiversity and is known as an "ecological killer". It has spread widely in China, including Zhejiang Province, Jiangsu Province, Shanghai City, Henan Province, Anhui Province, Hubei Province, Hunan Province, Jiangxi Province, Sichuan Province, Chongqing City, etc., especially in East China.
"If feed utilization is incorporated into the prevention and control system of Canadian goldenrod, it will play a big role." Liu Quanru, a professor at the School of Life Sciences of Beijing Normal University who participated in the research and compilation of the basic special project of the Ministry of Science and Technology "Invasive Flora of China", told reporters that the removal of Canadian goldenrod is very difficult, and "feed utilization" can not only use Canadian goldenrod as a plant resource, but also reduce the manpower and material resources generated by the eradication of Canadian goldenrod.
At a sheep farm in Lianshan Village, Daixi Town, Huzhou City, Zhejiang Province, people process Canadian goldenrod into fodder.
Beautiful and dangerous plants
About eight years ago, when Xiang Jizhong visited Ningbo, Taizhou and other places in northern Zhejiang, he saw the Canadian goldenrod for the first time. The plant impressed him, "Driving a car, you can see it from afar, because it is particularly tall, reaching a height of nearly 3 meters, with a long straight stem, with golden flowers on it, and as long as it appears, it is a large area." "The Canadian goldenrod that has not yet reached its flowering stage looks like an ordinary weed, and when it enters the flowering period in October, large areas of the plant will converge into a sea of golden yellow flowers.
The reason why the Canadian goldenrod appears in the fields and wilderness of China is directly related to its bright appearance.
In 1935, the Canadian goldenrod was introduced to Shanghai as a garden flower, and then from Shanghai to Nanjing, Wuhan, Dalian and other places. Professor Li Bo, Director of the Key Laboratory of Biodiversity and Ecological Engineering of the Ministry of Education, Fudan University, and others pointed out in their 2006 paper "Chrysopodium canadiensis: A rapidly expanding invasive alien plant" that the introduction of alien species as ornamental plants is one of the main ways of biological invasion.
In Liu Quanru's view, the Canadian goldenrod has "three strong", that is, strong reproductive ability, strong transmission ability and strong ecological adaptability. This is the reason why the Canadian goldenrod was introduced to Shanghai and became a weed and spread rapidly in many parts of China.
The Canadian goldenrod can reproduce both sexually and asexually, and both reproductive methods are very capable. When sexual reproduction takes place, through insect-borne pollination, a single Canadian yellow flower plant can produce more than 20,000 seeds per plant. Its seeds are crowned and hairy, small and light, "Now this season, there will always be something fluffy in the air around the Canadian goldenrod, like a dandelion, with a small parachute, which is actually its seed." Xiang Jizhong said that the seeds of a yellow flower in Canada will be scattered everywhere with the flow of people and vehicles.
Although it prefers to grow in acidic, low-salinity sandy loam and loam soils, especially in moisture-rich and sunny environments, it is also shade-tolerant, drought-tolerant, barren and ecologically adaptable, so it is common in farmland, gardens, wastelands, riverbanks, highways and railways.
As an invasive alien plant, the Canadian goldenrod has caused obvious harm to the ecology. The biological characteristics of the Canadian goldenrod make it more competitive in competing with native species in new environments, resulting in a significant reduction in native biodiversity. As early as 2003, the Shanghai Agricultural Technology Extension Center investigated and found that more than 30 species native to Shanghai had become extinct due to the invasion of the Canadian goldenrod.
The ravages of Canadian goldenrod in many places have also brought huge economic losses. Liu Quanru said that when the Canadian goldenrod invades the agricultural ecosystem, it will reduce the yield of the crops planted and the fruit trees cultivated, which also means the ensuing economic losses. In addition, the removal of Canadian goldenrod also requires a lot of human, material and financial investment.
In 2021, many places across the country launched a removal operation against Canadian goldenrod, among which the prevention and eradication operation in Wuhan was once on Weibo hot search. According to data from the Wuhan Municipal Bureau of Agriculture and Rural Affairs, as of November 20, 2021, in order to prevent the removal of Canadian goldenrod, Wuhan districts have raised 5.76 million yuan in disposal funds, with more than 24,000 participants and 438 sets of machinery.
In the fall of 2021, Daixi Town, Huzhou City, where Xiang Jizhong is located, also began a concentrated operation to remove a yellow flower. Wu Aimin, deputy director of the village committee of Lianshan Village in Daixi Town, Huzhou City, told reporters that in previous years, Canadian goldenrods appeared here only sporadically, but in recent years it has spread a trend, and in October last year, the local government launched the most intensive eradication operation in recent years. Wu Aimin said that Lianshan Village organized villagers to eradicate a yellow flower from Canada, with 100 yuan a day for female workers and 120 yuan a day for male workers, and for more than ten days, the village paid more than 80,000 yuan in labor costs.
Xiang Jizhong remembers seeing that the Canadian goldenrods removed from the village were piled up in the garbage disposal station, waiting to be sent to the government's unified disposal site, "I thought, can I use these Canadian goldenrods on the spot?" Xiang Jizhong dialed Jiang Yongqing's phone with questions. Jiang Yongqing is the director of the herbivorous livestock research office of the Institute of Animal Husbandry and Veterinary Medicine of Zhejiang Academy of Agricultural Sciences, and the president of the herbivore and grass industry branch of the Zhejiang Animal Husbandry and Veterinary Association, and has been engaged in the research and promotion of ruminant nutrition and breeding technology for more than 30 years.
The question Xiang Jizhong wants to clarify is: Can Canadian goldenrod be used as feed to lake sheep?
At a sheep farm in Lianshan Village, Huzhou, lake sheep eat feed processed from Canadian goldenrod.
"Perfectly usable as feed"
When he received Xiang Jizhong's call, Jiang Yongqing was not surprised by his questions.
As early as 2007, Jiang Yongqing's team had explored the feed application of Canadian goldenrod, which was studied as rabbit feed. At the beginning of that year, Jiang Yongqing went on a business trip to Cixi City, Ningbo City, and local rabbit farmers reported that there was a shortage of feed, and there were many Canadian goldenrods growing around the rabbit farm. According to local media reports in Ningbo at that time, the area of Canadian goldenrod in Ningbo City has reached as much as 70,000 mu, and the annual cost of Cixi City to treat Canadian goldenrod is as high as more than 6 million yuan. Jiang Yongqing suggested that rabbit farmers try feeding rabbits with Canadian goldenrod, and also collected some samples of Canadian goldenrod and brought them back to the unit for analysis.
Jiang Yongqing's team applied for a grant of about 200,000 yuan from the Cixi Science and Technology Bureau and carried out a series of experiments, including the determination of the main nutrients of Canadian goldenrod, the determination of the nutrient digestibility of Canadian goldenrod, and the study of the effect of feeding long-haired rabbits and rabbits in different proportions of Canadian goldenrod.
Jiang Yongqing's team finally concluded that Canadian goldenrod can be used as rabbit feed, with high nutritional value, and that harvesting is best in the period from August to October when yield and nutritional value are high. When feeding long-haired rabbits, the suitable dosage of Canadian goldenrod is 10%~20%, and when feeding rabbits, the suitable dosage of Canadian goldenrod is 11%~33%.
However, since then, the process of feed utilization of goldenrod in Canada has not moved forward.
When Xiang Jizhong contacted him, Jiang Yongqing's idea was that "Canadian goldenrod can be fed to rabbits as feed, and there is no problem for cattle and sheep." Jiang Yongqing explained that rabbits have a stomach, but a developed cecum can play the role of a stomach, and cattle and sheep have four stomachs, which have a stronger digestive ability than rabbits. ”
Jiang Yongqing asked Xiang Jizhong to feed the lake sheep with a small amount of Canadian goldenrod first, "mainly to see whether the sheep like to eat, whether it has an impact on growth, and how much is more appropriate." As for whether Canadian goldenrod is safe, digestible and nutritious as feed, Jiang Yongqing said these problems have been solved in previous trials. He sent Xiang Jizhong those papers that year.
In October 2021, Xiang Jizhong conducted a three-week trial on a sheep farm, setting up four control groups to observe the changes in feeding lake sheep with different proportions of Canadian goldenrod. After experiments, Xiang Jizhong found that Canadian goldenrod can completely replace sheep's roughage, with good palatability and high nutritional value.
After the experiment, because the removal work in Lianshan Village was nearing completion, Xiang Jizhong only fed the lake sheep with Canadian goldenrod for less than a week, but he had decided to prepare for the feed utilization of Canadian goldenrod in advance next year.
At the end of September 2022, Xiang Jizhong contacted the local government in advance, "The plucked Canadian goldenrod needs to be processed, and it can be directly pulled to my sheep farm." Wu Aimin said that this year's work to remove Canadian goldenrod in Lianshan Village began on October 15, and the villagers were still organized to eradicate this plant, but the difference was to adopt the method of purchasing and settle the villagers at the price of one kilogram and one yuan, so as to mobilize everyone's enthusiasm. In addition, after uprooting a Canadian goldenrod, it is tied and sent directly to the sheep farm.
Xiang Jizhong said that the sheep farm needs about 6 tons of Canadian goldenrod a day to feed, and the Canadian goldenrod sent by the village is more than 7 tons a day at most. Occasionally, when the village sent less than 6 tons of Canadian yellow flowers, Xiang Jizhong would take the initiative to find villagers to collect some, and also buy them at the price of one kilogram and one yuan in the village.
Because most of the time, Canadian goldenrod is collected by government organizations and sent to sheep farms for free feeding lake sheep, and the cost of feeding is significantly reduced. Xiang Jizhong roughly calculated that on average, sheep farms can save 100,000 yuan in feed costs a month.
Jiang Yongqing believes that the feed utilization of Canadian goldenrod can achieve many benefits. Economically, in addition to reducing the cost of feeding herbivores, it also reduces the cost of government control of Canadian goldenrod. Ecologically, because the feed is harvested before a Canadian goldenrod sets seeds, it can block its dispersal with the seeds and assist in the control of this invasive plant.
Jiang Yongqing said that more than a decade ago, the feed utilization of Canadian goldenrod did not move forward, there are many reasons, including that people at that time did not reach the current understanding of the harm it caused, and in the process of prevention and control, few people engaged in animal husbandry research put forward some new ideas for prevention and control, "If the government can take out the power to prevent Canadian goldenrod and promote its feed utilization, then there will be more and more parties to take this invasive plant as feed in the future." ”
The next crayfish?
In Lianshan Village, this year's work to control the Canadian goldenrod has basically ended. Wu Aimin said that the superior leaders are very positive about the current model of dealing with Canadian goldenrod, and it is expected that the plucked Canadian goldenrod will continue to be sent to sheep farms as feed next year.
Since the beginning of November, the media reported that Canadian goldenrod can be used as lake sheep feed, and so far the agricultural and rural departments of Jiangsu, Jiangxi, Anhui, Hunan and other provinces have contacted Xiang Jizhong and Jiang Yongqing, hoping to learn from the experience of dealing with Canadian goldenrod, and some places have begun to arrange field trips. On November 6, the Wuhan Municipal Bureau of Agriculture and Rural Affairs cooperated with a local animal husbandry company to carry out a Canadian goldenrod feeding experiment to cattle, and the cows reacted that they were not disgusted. The staff of the Wuhan Municipal Bureau of Agriculture and Rural Affairs told reporters that only preliminary tests have been carried out and are still waiting for the results.
In Jiang Yongqing's view, Canadian goldenrod has the potential to be promoted in the market as cattle and sheep feed, "because there is a breakthrough in technology, it has economic and social benefits, and the operation is simple, and it can be used to feed cattle and sheep after harvesting and crushing." Jiang Yongqing said that the nutritional value of Canadian goldenrod is close to that of peanut seedlings, northeast sheep grass and other feeds on the market, while Canadian goldenrod as feed, the cost is lower than the latter, can be replaced.
In order to promote the use of Canadian goldenrod feed, Jiang Yongqing's team will do a series of research next.
The first is a study of the digestion and compost fermentation of a Canadian goldenrod seed escaping ruminants. Some people have raised concerns that after feeding a Canadian goldenrod to sheep, will the seeds escape the digestion of the animals, and there is still a risk of transmission. Jiang Yongqing said that if a yellow flower is fed after seeding in Canada, some seeds may escape the sheep digestion and composting process, and he recommends using them before seeding, when the nutritional value is higher, or the sheep manure is fermented by high-temperature compost for a week. But in order to reduce the risk, Jiang Yongqing decided to do several related tests later.
There are also experiments to expand the feed utilization of Canadian goldenrod, and the experiment of rational utilization of Canadian goldenrod. Through current research, it has been confirmed that Canadian goldenrod can be used as feed for rabbits and lake sheep, and Jiang Yongqing said that the next step is to test whether it can be used as cattle feed, and the appropriate amount to add to the feed to solve the problem of how to make better use.
Another important study is the silage test. Jiang Yongqing said that the feed utilization of Canadian goldenrod is seasonal, and the endless use can be made into silage and stored. Xiang Jizhong believes that making silage can solve its long-term utilization problem, and it is possible to feed lake sheep all year round in the future, not just for a short month.
For a long time, when the domestic control of Canadian goldenrod was removed, feed utilization was not used as a solution.
Liu Quanru explained that there are three main ways to prevent Canadian goldenrod in China. The first is physical control, that is, the use of mechanical uprooting, generally seizing the opportunity of Canadian goldenrod just blooming and the seeds are not yet mature, quickly uprooting all plants, and removing the asexual reproductive organs such as rhizomes left in the soil through cultivation or excavation, taking them out of the field to dry and then destroying them centrally, and conditional fertilizer treatment. The second is chemical control, "which is also a more cost-effective means to control Canadian goldenrod", that is, the use of glyphosate and other biocidal herbicides and their compound agents during the emergence season and before and after flowering of Canadian goldenrod. "On the one hand, the use of herbicides to eliminate requires professional guidance, on the other hand, chemical control is easy to cause certain harm to the environment, if it is not a large-scale outbreak, it is not recommended." The third is biological control, which is controlled by introducing natural enemies, "but accidentally causing new biological invasions", Liu Quanru suggests alternative planting methods, such as planting fast-growing trees and shrubs, and when they grow up, they can achieve biological replacement through effective competition and shade.
Liu Quanru believes that feed utilization can become a way for the Canadian goldenrod, an invasive alien plant, to be rationally utilized. However, he also said that feed utilization is mainly used as a supplementary means of biological control, completely relying on feed utilization to prevent and control, I am afraid that it will not achieve the expected purpose, "because of the prevention and feed utilization, the goals of these two things are inconsistent." Liu Quanru said that the prevention of Canadian goldenrod is to control its spread, but when it is used as a resource, it is hoped that the more plant resources, the better, which may lead to artificial planting.
When it comes to invasive species that need to be removed in captivity, people often think of crayfish, is it possible that the Canadian goldenrod will become the next crayfish? The crayfish industry has been booming in recent years, and the "China Crayfish Industry Development Report (2022)" compiled under the guidance of the Fisheries and Fisheries Administration Bureau of the Ministry of Agriculture and Rural Affairs shows that the total output value of the mainland crayfish industry in 2021 reached 422.195 billion yuan, a year-on-year increase of 22.43%, and higher than the level in 2019.
Liu Quanru said that in fact, eating crayfish has not achieved the purpose of biological control. Crayfish on the table are still farmed in captivity, not caught in the wild, and wild crayfish cannot be eliminated by being eaten, "not that they can be used commercially, there is no biological invasion problem." ”
If the future economic value is highlighted, what needs to be considered is how to reduce the ecological harm caused by Canadian goldenrod, "so when using it, even if it is planted artificially, it is necessary to avoid letting it enter the natural ecosystem to prevent spread." ”
(Source: China Newsweek, original title "Will this "delicious" invasive species be the next crayfish?") 》）