Richard Linhart Bollinger, An American veterinary specialist
He graduated from Purdue University and received continuing education in clinical nutrition and veterinary immunology at Iowa State University, the University of Nebraska, and the University of Missouri. Linhart is a member of the American Association of Cattle Physicians, the College of Veterinary Consultants, the American Society of Biologists and the American Veterinary Association. Prior to joining Boehringer, he worked at Zoteng and Merria for 10 years and at Simpsonville Animal Hospital LLC for 20 years, which serves cows with calves, lactating cattle, fattening beef cattle, horses and exotic animals. He specializes in advising and executing concurrent estrus programs to optimize the outcomes of artificial insemination and embryo transfer. Familiar with antimicrobials for the prevention and control of newborn bovine diseases, fattening beef cattle health management, parasite control, vaccines, anti-infection and reproductive health. He is also an aspiring pilot, metal artist, mainly interested in welding metal sculptures.
In the beef cattle production system, factors related to the actual production efficiency include: retention rate of calves when weaned, weight of the calves, calf prices, feed costs, interest, weight of eliminated cattle, price and so on. Studies have shown that of the 150 different factors that affect cattle profits, the largest cost is feed costs, the minimum cost is animal health costs, and in general, cattle farms need only 2.5% of the production input for animal health. Research shows that investments in improving animal health pay off to producers, with producers with high rates of return spending more on animal health than producers with low rates of return, that is, producers who spend more on animal health tend to get more benefits than producers who spend less on animal health. For beef farms, parasite control is one of the important aspects of the process of having a particularly low input but yielding a large output.
<h1>Why deworm cattle? </h1>
The nutrition and physical condition (body weight) of cattle determine their reproductive performance, and the first important thing in beef cattle benefit ranking is the weaning weight of calves and the reproductive performance of cows. Parasites compete for nutrient resources in beef cattle, reducing beef cattle feed intake and affecting calf growth and cow milk production. In addition, beef cattle infected with parasites can reduce the animal's feed conversion rate, affecting their immunity and the effect of vaccine use, while immunocompromised cattle are more likely to suffer from respiratory diseases.
Effects of parasitic infections on calves and cows
In the U.S. beef cattle production system, all calves need to be accurately weighed by an electronic scale when trading, which means that the weight of the calves to be sold after weaning represents the economic benefits of beef cattle producers. Deworming calves is for better growth and more weight gain, as well as to make calves look better in coat color and health, and have a better price when trading. For fatting farms, deworming when all cattle are bought into the farm is an essential task. Deworming a cow is given to improve its nutritional status and thus achieve better reproductive performance, while producing more milk, which is also more beneficial to calf growth. However, U.S. cow farms often overlook that only breeding bulls are dewormed, and in fact, the performance of deworming and breeding together with cows and bulls will be better improved.
Deworming can not only improve the health of cattle, but also bring some tangible economic benefits. Studies have shown that parasite deworming investment in the entire beef cattle production and breeding process is the highest return on investment, up to 10:1, that is, 1 yuan investment in deworming can get 10 yuan of income. Data show that calves that bring 0.2-0.4 kg of daily weight gain improvement after repelling the internal parasites, and by the time of weaning, the repellent calves can bring 9.2 kg of weight gain. Studies have also shown that the diameter of the pelvis increases by 7.5% after cows are dewormed, reducing problems in calving; it can improve weight gain and increase the physical condition score by 0.2. It can also accelerate the arrival of the first love period and improve the pregnancy rate, ranging from 2.4% to 120%. According to a study in the United States in 1996, the pregnancy rate of cows in the experimental group (regular deworming) and control group (without deworming) reached 94.2% in the experimental group and 82.1% in the control group, a difference of about 12%.
Figure 1 refers to the fact that during the cow breeding season, different physical fitness scores have different adaptation rates, of which the horizontal axis represents the cattle physical fitness score and the vertical axis represents the adaptation rate. As shown in the figure, with a physical fitness score of 3.5 points, only about 25% of cattle can start breeding, while when the physical fitness score is 6 points, 80% of the cattle have already begun to breed. There are two ways to improve the physical fitness score: one is to feed the cow more and better feed, and the other is to deworm it to make it have better nutritional improvements. Needless to say, deworming is a better way to improve your physical fitness score with less investment and better economics.
Figure 2 shows the change in physical performance score. In the American calf production system, in general, the spacing between the tires is 90 days (one cow per year) is more reasonable. As can be seen from the figure, if the bovine physical fitness score is 5.5 points, the postpartum physical condition score does not show any performance, then the fetal spacing is about 89 days, which is the most appropriate value. In other cases, such as when the physical condition score is not very good, regardless of whether the postpartum physical condition score increases or decreases, the number of days of first estrus will be larger. It should be emphasized here that for cows, if a more appropriate physical score (such as 5.5 points) can be maintained, it does not need additional supplementation after calving, and it can achieve better production indicators.
Effects of parasitic infections on the immune system
Substances released after parasite infection are identified by the immune system as foreign antigens and are rejected by the immune system, thus affecting the body's immune system. In addition, for pregnant cows, if a parasitic infection occurs, these immune-suppressing components produced by the parasite can penetrate the placental barrier to the fetus, and even if the fetus is not infected with the parasite, the immune system will be affected after birth.
<h1>Life cycles of common bovine parasites</h1>
Parasites form a cycle between cattle and grass, when cattle inadvertently eat grass contaminated with parasite larvae will be infected (including parasite larvae, the first and second stage larvae grow and develop in cow dung), immature worm larvae migrate to the intestinal wall, after 21 days of development into adult worms, adult worms lay eggs in the digestive tract, the eggs enter the feces and excrete into the grass, and after about 7 days of development, they become infected again. This is also the third stage of the parasite's life cycle, in which infected larvae develop within 1 week and follow precipitation in cow dung or grass, remaining infected for weeks or even months. Cattle ingesting stage III larvae while grazing are infected.
There are also some parasites that can be in a latent state, hiding in the stomach wall of the animal's real stomach, waiting until the weather warms up to break out of the wall, and then develop into adult worms and continue to lay eggs. Parasites are animals with very tenacious vitality, and they can survive in particularly hot weather or when the outside world is particularly cold. In particular, parasitic larvae in the third stage can survive for several days or even years, and some studies have found that some nematodes and Cooper's larvae can survive in the external environment for more than two years. For parasites, generally 7-25 degrees Celsius is a more suitable temperature for its growth. Storms can activate eggs in dried cow dung (moisture easily activates dormant parasite larvae), and most of the larvae in the infection phase of grazing come from fresh cow dung. In places where the environment is particularly harsh, even in deserts or places where it is cold, there will be parasites to survive.
As cattle grow, they gradually develop resistance to some parasites. Young cattle are more susceptible to parasites, and it is particularly important to deworm young animals. Parasites such as nematodes can parasitize various places in the bovine, such as lung nematodes parasitizing in the lungs, Osteriasis parasitizing in the true stomach, there will be other kinds of parasites in the cecum and small intestine, different kinds of parasites in different places will cause different symptoms, but, in most cases, if the parasitic infection of cattle does not reach a high load, the cow may not show any external symptoms.
<h1>Essentials of parasite control and management</h1>
For grazing beef cattle farms, 90% of the parasite population exists in the pasture, 10% of the parasite population exists in the animals, the grazing cattle are constantly infected by the grassland, and need to be dewormed many times, in general, the grazing cattle need to be dewormed 1-2 times a year, and the cattle in the house can be dewormed when they enter the farm.
Spring deworming is important. It can effectively reduce the contamination of grassland by larvae. Figure 3 shows the importance of spring deworming in cattle farms under grazing conditions, the yellow part represents the parasite larvae that have survived the harsh winter, and as spring arrives, the temperature warms up, and the parasite larvae present in the pasture re-infect the cattle, and eventually excrete into the grassland through feces, resulting in a very significant increase in the number of parasite colonies present in the grassland (Figure 3 left). If these adult cattle are dewormed in the spring, they will be killed even if they have ingested larvae in the infectious stage and will not ovulate again, and the load of parasites in the grassland will be significantly improved, maintained at a low level (Figure 3 right). In addition, for grazing calves, spring deworming also has a very important role: parasites will suppress appetite, after the deworming cows eat more, produce more milk, reproductive performance is also improved, calf health will also be improved, calves will have better benefits when they are sold.
How can you assess whether a pasture deworming regimen is effective? A common method in the United States is called fecal egg reduction testing, which measures fecal egg counts 28 days before treatment and after treatment (pest control), and compared with the results of the two times, the parasite load should be reduced by more than 90%. It can also be assessed by measuring production, compared to dewormed and non-dewormed animals, the daily weight gain of dewormed calves can be improved by 0.1 kg.
Many farms will have such a question: our pasture has done a fecal egg count, but no eggs have been found, do we still need to deworm? Some experimental data show that even if no eggs are found when the farm is counted, the growth performance of the cattle will be significantly improved after the insects are expelled. Why is this happening? Here it is necessary to remind everyone that parasites do not reproduce and lay eggs every day, sometimes the amount of parasitic infection may be very high, but due to the unsuitable external conditions, these parasites will temporarily stop breeding and laying eggs, so we can not find that there are eggs in the feces, in fact, animals still have a high load of parasitic infection. In addition, fecal eggs are also very directly related to the number of adult worms in the animal, and non-adult worms do not lay eggs. In addition, different types of parasites lay different numbers of eggs, some may lay 50 eggs a day, and some may lay 5,000 eggs a day.
The fecal worm egg reduction test has been used in the United States for many years, and sometimes the effect is not particularly good. In the case of pest extinction, it has been used in the United States for nearly 40 years, there are already some resistant parasites, and sometimes the egg reduction rate test results are not particularly good, and then we will use pest control and other product combinations. If there are different groups of cattle on the ranch, the best test is young cows, because young animals are more susceptible to parasites and do not develop resistance.
Under what circumstances do fecal egg reduction rate tests be done? Special attention should be paid to the following three aspects: cattle - when cattle only show symptoms associated with parasitic diseases, such as back hair confusion, growth performance is much worse than expected to do testing; grazing - grazing high-risk animals for more than a month, the best time point is in the spring, the grass turns green a month or two to do testing; drug aspect - 2-4 weeks after deworming to assess the effect of deworming using fecal egg counting.
In addition to the stool worm egg count test, weighing testing is also the most commonly used method in the United States. The animals were divided into two groups, the deworming group or the non-deworming group; A deworming or B deworming, and then the daily weight gain of cattle was compared. For us, weighing methods may be a more common approach, because the ultimate source of benefit for the pasture is the weight gain of the cattle.
Autumn deworming is also important. The parasites that dormant in the cows at the end of summer recover after the autumn weather turns cool, and then develop into adult worms, lay eggs, discharge insect eggs, the grassland is polluted, and the cool climate will lead to increased grazing, so autumn is also the best time to drive away cattle lice. In addition, under the American beef cattle production system, autumn deworming also has a very important point, autumn is the time for American beef cattle farms to concentrate on processing cows and calves, because their cow breeding is concentrated in the external pasture, usually will not interfere, until the autumn will concentrate on the discount calves for weaning, weighing, selling and other operations, therefore, in the autumn deworming is a convenient time point.
<h1>How do U.S. beef cattle farms deworm? </h1>
The usual practice is that for fattening farms, they will use 1% pest extermination (active ingredient ivermectin) when the cattle enter the farm for deworming. For breeding cow farms, the calves are about 2-3 months old each spring and deworm at 100 kg of body weight. In autumn, the calves are weaned at about 250 kg and dewormed again. Basically all cow farms deworm cows in the fall and sometimes again in the spring.
1% pest control can kill 99% of gastrointestinal nematodes and Osteriasis stage 4 larvae, effective against maggots and vampire lice, but less effective against gnats, less effective on adult horned flies (can kill larvae in feces), effective against adult thread neckworms (less effective against L4 stage larvae).
Mechanism of pest extinction: It has good affinity and selectivity for glutamate chloride ion channels in invertebrate nerve and muscle cells, increases the permeability of cell membranes to chloride ions, depolarizes nerve and muscle cells, and eventually paralyzes and kills parasites.
The safety of pest extinction is very high. First, mammals do not have glutamate chloride channels, macrolide drugs have a low affinity for chloride channels of other mammalian complexes, and the drugs do not penetrate the blood-brain barrier. Does one wonder or worry about whether the use of deworming drugs on pregnant cattle will lead to their miscarriage? In fact, there will be no impact at all, and from more than 40 years of experience in the United States, it has never been heard that the use of harm can lead to miscarriage.
Compared with similar ivermectin products on the market, from a chemical point of view: there are more active ingredients in the pest, the carrier is safer and more effective, and the United States has data showing that putting in a needle to kill the pest can basically bring about growth performance improvement and recover the investment; from the packaging point of view, the package of the pest can avoid light and oxygen; from the performance point of view, the pest extinction can bring higher daily weight gain and parasite killing effect.
(This article is based on expert lectures at the "2nd Boehringer Ingelheim Beef Cattle Health and Nutrition International Forum")