On this episode of Bovine Science Dr. Phillip Lancaster brings a research article studying the effects of a Bacillus-based direct-fed microbial on digestibility. Dr. Brad White and Dr. Lancaster will discuss the results of this research as well as how it could help cows on forage.
Article Discussed: https://doi.org/10.1093/jas/skaf093
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| Bob Larson, DVM, PhD Reproductive physiologist and Epidemiologist Beef Cattle Institute Kansas State University RLarson@vet.k-state.edu |
Although most of the time when we administer a treatment, vaccine, or other product to cattle we expect a positive outcome; occasionally cattle will have an adverse drug reaction. Adverse reactions can occur following the use of injectable antibiotics, dewormers, vaccines, insecticides, vitamin preparations, anti-inflammatory preparations, as well as skin ointments and other classes of drugs.
Adverse drug reactions are defined as any unintended and undesirable response to a drug and can be somewhat grouped as to being “human error” or “random”. Human error is often suspected if a high percentage of a group of cattle have an adverse drug reaction. The error can be due to an improper dose, route of administration, or combination of drugs. Improper dose can occur when a dose that is safe for another species results in an unsafe dose for cattle. Also, certain diseases such as liver or kidney disease or old age can cause a normally safe dose to cause problems in some individuals.
The label of any veterinary product will include instruction on the route of administration. The route can be: by mouth, applied to the skin, or injected into a muscle (intramuscularly/IM), under the skin (subcutaneously/SQ), or into a blood vessel (intravenously/IV). If a drug or product is labeled for one route of administration but given by another route, dangerously high doses of the active ingredient or other components of the product can result. It is important to understand that a veterinary product contains more than the active ingredient – it will also contain ingredients to keep the product stable over time and over a range of temperatures and other factors; and some non-active ingredients can be toxic at high doses.
Drug interactions can occur when one or more drugs antagonize another drug making it either ineffective or even dangerous. This can occur when drugs that were not intended to be mixed are mixed together in a bottle or syringe. The active drugs or the additives may cause the antagonism. Drug interactions can also occur even if antagonistic drugs are not mixed before injection, but are injected into the same animal and interact within the animal to cause adverse reactions.
You can reduce the risk of human error causing adverse drug reactions by only using drugs that you are very familiar with and that you have been trained to use by your veterinarian. Also, never mix drugs together in a bottle or syringe unless directed by the label. And, avoid giving multiple drugs at the same time unless your veterinarian advises you that it is safe.
Adverse drug reactions can also be caused by random, unknown factors. These types of reactions usually only affect one or a few members of a herd or group, but can cause a cluster of affected animals due to similar genetic factors in related animals. These types of reactions are unrelated to the dose or normal effects of the drug; and they are probably impossible to prevent. The active ingredient or carriers and other additives may cause random effects such as allergic reactions.
Allergic drug reactions in cattle most commonly occur following an injection and result in fluid build up in the lungs. The animals have sudden and severe respiratory problems making it difficult for them to breath. This type of reaction is called an anaphylactic response and often results in death. Rapid treatment with epinephrine and supportive care may help some affected cattle to survive.
Because the risk of adverse drug reactions is always small but present. Cattle should be observed after being treated with any veterinary product and not allowed to immediately leave the sight and care of the producer or veterinarian. Careful and appropriate use of veterinary products and attention following treatment are necessary to minimize the risk and cost of adverse drug reactions.
Welcome to BCI Cattle Chat! On this episode the experts dive into options producers have when faced with open cows. Next, they discuss acute interstitial pneumonia, Dr. Lubbers brings some new findings in research and the experts decide what could be coming in the future. Finally, Dr. Pendell answers a listener question which asks the amount of producers who have switched to growing row crops.
2:21 Open Cows: Loss or Treasure
10:58 Acute Interstitial Pneumonia
15:56 Listener Question: Crops
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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What causes 30-40% of pregnancies to not have a live calf? Dr. Bob Larson brings a research report article which summarizes a lot of information on pregnancy in beef cattle. Dr. Brad White and Dr. Larson will discuss new information that could be applicable when dealing with pregnancy loss in a herd.
Link to Article: Highlighting factors contributing to pregnancy loss in beef cattle
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Welcome to BCI Cattle Chat! On this episode the Jacob Schumacher is here to talk about his research on castration and pain. Next, Dr. Bob Larson answers a listener question regarding narrowing the calving window. Finally, the experts answer another listener question from a producer who wants to convert to a registered herd. Thanks for tuning in and enjoy the episode!
3:13 Jacob Schumacher Research Update
9:34 Listener Question: Calving Window
17:40 Listener Question: ET vs. AI
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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After moving 700 pound stocker cattle to crop residue the producer found eight of them dead. What caused it, and can they put animals out there again? Find out on this episode of Tox Talk a Bovine Science Podcast with Dr. Brad White and Dr. Scott Fritz? Thanks for tuning in and enjoy the show!
The toxicology website and Bovine Sciences with BCI podcasts have been sponsored in part through a veterinary services grant that Dr. Scott Fritz, Dr. Steve Ensley and Dr. Bob Larson have received to share more toxicology information and examples for people to understand what to submit and how to submit. Another part of that grant has been working with people and producer in the field.
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Welcome to BCI Cattle Chat! Dr. Brian Lubbers begins the episode by discussing Hairy Heel Warts in feedlots. He explains what could cause them and how it can be treated. Next, the experts discuss bulls composition and BCS for cows versus bulls. Finally, Merri Beth Day is back to discuss her research on sustainability in the cattle industry. Thanks for tuning in and enjoy the episode!
2:25 Listener Question, Hairy Heel Warts
11:18 Bull Composition
15:58 Sustainability with Merri Beth Day
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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This producer moves his cows out to cornstalks and the next day gets a big snow. When he goes to check on them the next day there are 14 dead. Dr. Scott Fritz and Dr. Brad White get to the bottom of the case in this episode. Thanks for tuning in and enjoy the show!
The toxicology website and Bovine Sciences with BCI podcasts have been sponsored in part through a veterinary services grant that Dr. Scott Fritz, Dr. Steve Ensley and Dr. Bob Larson have received to share more toxicology information and examples for people to understand what to submit and how to submit. Another part of that grant has been working with people and producer in the field.
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Welcome to BCI Cattle Chat! On this episode the experts answer your listener questions. They start by discussing what age you should castrate calves and what vaccinations could be given. Next, Dr. Brian Lubbers and Dr. Phillip Lancaster discuss feeding heifers and some of the challenges that come along with that. Finally, they discuss average daily gain as well as feed to gain ratio. Thanks for tuning in and enjoy the episode!
3:00 Castrating Calves
11:10 Feeding Heifers
15:54 Average Daily Gain
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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Understanding the overall sustainability of beef production is important for making continuous improvement allowing documentation of improvement over time. A couple of recent studies estimated the overall sustainability metrics of beef production in the US (Rotz et al., 2019) and Canada (Aboagye et al., 2024). In both countries, methane emissions were the primary greenhouse gas emitted, with the cow-calf sector accounting for more than 50% of the total. The primary use of fossil fuel energy was feed production in both countries. Additionally, the primary use of blue water was feed production in both countries. Blue water is surface or ground water used for irrigation, cattle drinking, and cleaning of facilities and equipment: it does not include green (rain) water that falls on crop fields and pasture.
Even though beef production in the US and Canada may seem relatively similar, there are subtle differences. For example, growing cattle in Canada may spend fewer days on pasture consuming high roughage diets leading to lower methane emissions. Feed production in the US uses more fertilizer per acre of arable land leading to greater fossil energy use. And the US uses more freshwater for agriculture production than Canada. The difference between the US and Canada in climate conditions is the primary driver in the differences in overall sustainability metrics.
Dr. Phillip Lancaster brings us an article out of China that looks at what effects diet has on calves rumination and overall health. The study looks at calves with and without forage inclusion. They discuss the research procedure and how the results could apply to beef calves in the U.S.
Article Discussed: How neonatal diet affects the long-term development of rumination behavior, rumen fermentation and feed digestion in dairy calves fed a high milk level?
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On this episode of Cattle Chat we have another amazing guest, Dr. Juliana Ranches, who is an Assistant Professor at Oregon State University. She talks to us about virtual fencing and how it works. Then, Dr. Pendell asks the hosts some questions about the Cattle Inventory report. Finally Dr. Ranches discusses her research on the effects of exposure to smoke in cattle. Thanks for tuning in and enjoy the episode!
3:15 Virtual Fencing
12:10 Cattle Inventory Report
16:32 Smoke and Cattle Health
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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In this episode of Herd Health a Bovine Science podcast Dr. Bob Larson and Dr. Brad White breakdown open cows. They talk about how to figure out what causes a cow to not be pregnant. They also discuss what to do once you find the problem.
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| Bob Larson, DVM, PhD Reproductive physiologist and Epidemiologist Beef Cattle Institute Kansas State University RLarson@vet.k-state.edu |
A disease associated with lush early-season grass in many parts of North America is Grass Tetany. This disease is also called Grass Staggers or Hypomagnesemia and is caused when blood levels of the mineral magnesium become low due to a combination of plant and animal factors. Observed most frequently in the early spring when soil temperatures are low and forage is growing fast, the grass has low levels of magnesium and sodium and high levels of potassium. This combination can lead to low blood levels of magnesium and the affected cattle can show signs of nervous systems problems such as staggering, convulsions, and being down and unable to rise, and if not treated within a few hours, can result in death.
Although young, growing animals can occasionally be diagnosed with Grass Tetany (particularly if grazing grasses associated with grain production such as wheat, rye, or barley), lactating cows are the most commonly affected. Milk contains relatively high levels of magnesium and cows in late pregnancy and early lactating cows have a high dietary requirement for the mineral. In addition, deficiencies of calcium or phosphorus, which are also required in high amounts in lactating cows, will increase the risk for Grass Tetany. If a heavy-milking cow is grazing forages that are low in magnesium, it can easily become deficient in magnesium.
In cases of Grass Tetany, soil levels of magnesium are typically not deficient. But soil temperature affects magnesium uptake into the plants, and grass tetany is associated with early spring before soil temperatures are consistently warm or occasionally when warm spring weather is followed by several days of cold weather. Cool season grass pastures, particularly if fertilized with nitrogen or a spring application of potash are most commonly associated with Grass Tetany. However, even cows on unfertilized native grass pastures can have the disease if heavy spring rains promote rapid early forage growth. Forages that are prone to causing grass tetany are deficient in magnesium and sodium and have an excess of potassium. Potassium, which can be very high in lush, early-growth forage, interferes with magnesium absorption from the gut, further decreasing the amount of magnesium available to the cow.
The first signs you might see in a cow with Grass Tetany is nervousness, appearing overly-alert, and a stumbling gait. These signs progress to more evidence of restlessness and possibly aggressiveness. An affected cow’s gait may vary from being stiff-legged, to high-stepping, to staggering. An animal that has fallen and is unable to rise and has convulsions must be treated soon to prevent death. And in fact, because of the rapid course of the disease, simply finding dead cows with no previous signs of illness is commonly the first indication that you have a problem.
If cattle are identified early enough in the disease, treatment with a solution containing magnesium given into the vein will likely prevent death. If a cow has been down several hours, the outlook even with treatment is not as positive. A cow that was down or staggering but that was treated successfully by injecting a solution with high levels of magnesium and other minerals directly into a vein can appear better for a few hours and then the condition can return. To avoid these relapses, additional magnesium is usually
given by another route such as an oral paste, an enema with a magnesium sulfate or magnesium chloride solution, or subcutaneous administration of a high-magnesium solution.
As a preventive strategy, cattle (particularly late gestation and early lactation cows) grazing wheat, rye, or other cereal grain pastures or lush early-grow cool season grasses should be fed a mineral supplement that is high in magnesium for about 30 day prior to turn-out and while they are grazing forage that has a high risk of inducing Grass Tetany. It is important that cattle have a daily supply of high-magnesium mineral while Grass Tetany is a risk; so check mineral feeders frequently to avoid cattle running out of their magnesium source. Magnesium oxide is the most common source of magnesium used in cattle mineral mixes, but cattle don’t like the taste and it must be mixed with molasses, grain, soybean meal, or other palatable feed. Magnesium supplementation should continue until soil temperatures remain consistently high and forage growth has slowed.
Grass Tetany is a serious disease of cattle that can result in rapid death in a few to many cows in a pasture. It is important to know the situations, forage types, and fertilization strategies that are most likely to be associated with Grass Tetany, and to have a plan to prevent problems with appropriate mineral supplementation.
Welcome to BCI Cattle Chat! We are joined this week by Associate Professor Dr. Pedro Fontes sponsored by ESTROTECT. He and Dr. Bob Larson start the episode by discussing common synchronization problems. Dr. Brad White then asks Dr. Fontes about some of his research on sire nutrition and fertility. The experts finish the episode by discussing what causes pregnancy loss in the first trimester. Thanks for tuning in and enjoy the episode!
3:41 Common Synchronization Problems
11:38 Sire Nutrition and Fertility
17:43 Pregnancy Losses in the First Trimester
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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In this episode of Bovine Science Dr. Brian Lubbers brings a research paper requested by a listener. This paper published in the Journal of Animal Science is titled, “Administering the maternal bovine appeasing substance improves overall productivity and health in high-risk cattle during a 60-d feedlot receiving period.” Thanks for listening!
Link to article: https://doi.org/10.1093/jas/skae221
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Welcome to BCI Cattle Chat! On this episode Dr. Bob Weaber is back to talk about genetics and selection. We also get a research update from Merri Beth Day where she discusses the economic implications of disease in feeder cattle. Thanks for tuning in and enjoy the episode!
2:25 Heifer Listener Question
11:44 Bull Selection at a Sale
16:35 Research Update
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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As this producer gets ready for the snow they discover that 11 of their cows are lame. What caused it, and how can they keep the other 30 cows from going lame? Find out on this episode of Tox Talk a Bovine Science Podcast with Dr. Brad White and Dr. Scott Fritz? Thanks for tuning in and enjoy the show!
The toxicology website and Bovine Sciences with BCI podcasts have been sponsored in part through a veterinary services grant that Dr. Scott Fritz, Dr. Steve Ensley and Dr. Bob Larson have received to share more toxicology information and examples for people to understand what to submit and how to submit. Another part of that grant has been working with people and producer in the field.
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Both the rumen microbes and animals need protein for maintenance and growth. In reality, they both need amino acids, which are the building blocks of protein. Microbes can use amino acids from digestion of feed protein or can synthesize amino acids from non-protein nitrogen such as urea. The animal must use preformed amino acids, it cannot synthesize amino acids from non-protein nitrogen. Preformed amino acids can come from digestion of feed protein or microbial protein.
In ruminant animals feed protein is either degraded in the rumen by microbes, termed rumen degradable protein, or digested in the small intestine of the animal, termed rumen undegradable protein. All feeds have some rumen degradable protein and some rumen undegradable protein, but varying the proportion of each. For example, soybean meal protein is approximately 75% rumen degradable protein and 25% rumen undegradable protein, whereas, dried distillers grains protein is approximately 40% rumen degradable protein and 60% rumen undegradable protein. Feeds like urea that are termed non-protein nitrogen are 100% rumen degradable protein.
In animals, amino acids are not stored in the body like carbohydrates are stored as fat. If amino acids are not needed for protein synthesis, the amino acids are broken down in the liver and the nitrogen in the amino acids are excreted in the urine. However, ruminant animals have the ability to recycle this nitrogen back to the rumen where microbes can convert the nitrogen to amino acids again. In this way, extra amino acids can provide microbes with the nitrogen they need for maintenance and growth.
Research has demonstrated that feeding 2 times the requirement of rumen degradable protein every other day provides the same response in low-quality forage digestion and intake as feeding the daily requirement of rumen degradable protein every day. The same response is due to the ability of cattle to recycle the excess amino acids/nitrogen for the microbes to continue to growth on the non-feeding day. Additionally, rumen undegradable protein can also be recycled, and potentially more efficiently because of slower rates of digestion.
A recent study evaluated whether adding a source of rumen degradable protein in the form of urea to a high rumen undegradable protein feed improved performance of calves grazing low-quality (crude protein ~6%) corn residue. Adding urea to dried distillers grains provided no improvement in growth of calves (Figure 1; Trial 1). In a subsequent trial, feeding dried distillers grains resulted in the same average daily gain as feeding a combination of SoyPass and soybean meal (Figure 1; Trial 2). SoyPass is a modified soybean meal product to increase the rumen undegradable protein proportion to 75%. The SoyPass/soybean meal combination provided mathematically a balance of rumen degradable and undegradable protein without accounting for the nitrogen recycling.
Cattle have the ability to recycle nitrogen from both rumen degradable and rumen undegradable protein. Feeding adequate protein from dried distillers grains does not require additional rumen degradable protein.
Welcome to BCI Cattle Chat! On this episode the experts dive into managing your yearling bulls. Next, they answer a listener question about adapting your mineral program throughout the year. Finally, the experts give some tips on handling fall born calves. Thanks for tuning in and enjoy the episode!
2:16 Yearling Bulls: Bull Value Cow-Q-Lator
11:05 Listener Question: Mineral Program Adaptation
15:56 Managing Fall Born Calves
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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Dr. Bob Larson brings us another mysterious episode of Herd Health a Bovine Science podcast. In this episode we have 20% of a herd come up open. Dr. Brad White and Dr. Larson discuss how this happened and what you can do to prevent this occurring in your own herd. Thanks for listening and enjoy the show!
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Welcome to BCI Cattle Chat! On this episode the experts are joined by another great guest Dr. Ty Lawrence Caviness Davis Distinguished Chair in Meat Science at West Texas A&M. They start the episode by discussing the changes in cattle overtime and how cattle may look in the future. Next, Dr. Brad White asks the experts about carcass size and what size should producers aim for. Finally Dr. Lawrence talks about some diseases he sees in the packing plants and how they compare to what we see at the BCI. Thanks for tuning in and enjoy the episode!
2:47 Evolution of Carcass Composition
10:52 Optimal Carcass Size
15:54 Diseases in Fed Cattle
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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This episode of Diving into Diets Dr. Phillip Lancaster brings a research paper which studies patch burning. They discuss how patch burning affects the nutrition value added for cattle. They also discuss what this would mean for the future of grazing cattle.
Article Discussed: Improving forage nutritive value and livestock performance with spatially-patchy prescribed fire in grazed rangeland
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Welcome to BCI Cattle Chat! This episode one of our students Liliana Rivas joins to tell us about her research with beef-dairy cross calves. Next, Marshall Stewart is back to tell us about K-State’s new project with Garden City Community College. Dr. Lancaster finishes the episode by answering a listener question concerning a cow feed program. Thanks for tuning in and enjoy the episode!
3:00 Liliana Rivas Research Update
10:05 Marshall Stewart: Garden City Partnership
16:48 Listener Question: Feed Program
For more on BCI Cattle Chat, follow us on X at @ksubci, Facebook, and Instagram at @ksubci. Check out our website, ksubci.org. If you have any comments/questions/topic ideas, please send them to bci@ksu.edu. You can also email us to sign up for our weekly news blast! Don’t forget if you enjoy the show, please go give us a rating!
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| Bob Larson, DVM, PhD Reproductive physiologist and Epidemiologist Beef Cattle Institute Kansas State University RLarson@vet.k-state.edu |
Having a highly productive herd that optimizes reproductive efficiency and forage and feed resources should be the goal of every cow-calf operation. Achieving this goal requires attention to many aspects of herd management including: heifer development, bull management, breeding soundness examinations of both bulls and heifers, forage management, forage supplementation strategies, and control of diseases that can cause infertility, early embryonic death, abortions, or the birth of weak calves.
When a fertile bull mates a fertile cow, many times a live calf is not born from that mating. If the bull and female are both fertile (i.e. producing fertile eggs and sperm), nearly 100% of matings will result in the start of a new embryo. But reproduction is complex and there are many opportunities for problems to arise that halt the normal progression of the pregnancy. In fact, it is estimated that about 30-40% of embryos are lost very early in pregnancy. If the pregnancy is lost in the first 14 days, the cow will usually be in heat again 21days after her last heat and if the bull is still in the breeding pasture, she will be bred again and have another 60% to 70% likelihood to initiate and maintain a pregnancy. This early loss is considered unavoidable and is due to the complexity of reproduction and the loss of imperfect embryos.
Because only 60 to 70% of fertile matings will result in the birth of a live calf, it is important that all or most of the cows in the herd have the opportunity to be bred three times before the bulls are removed from the breeding pasture. Using a 65-day breeding season as an example, cows that cycle within the first three weeks of the breeding season have the opportunity to re-cycle by day 42 if they lose an early pregnancy from the first mating and again by day 63 if they lose a second pregnancy – resulting in three opportunities to get pregnant and maintain a pregnancy all the way to calving. In contrast, cows that do not start cycling until the second 21 days of the breeding season only have one more opportunity to be bred if they lose the first pregnancy early enough to re-cycle. Using an average of 65% successful births of a live calf from fertile matings, 95% of cows that have three opportunities to become pregnant will give birth to a live calf. In contrast, only 88% of cows that only have two opportunities to become pregnant are predicted to give birth to a live calf.
To ensure that a high percentage of cows with calves at-side and first-calf heifers are cycling at the start of the breeding season, it is critical that they calved early in the calving season in good body condition. Remember that pregnancy in cattle lasts about 283 days; which leaves only 82 days between the birth of a calf and a mating that results in a successful pregnancy for next year’s calf if the cow is to maintain a one-year calving interval. Although there are herd-to-herd and year-to-year variations, most herds require about 50 to 70 days after calving for a majority of mature cows in good body condition to resume cycling. First-calf heifers require more time to resume fertile cycles
after their first calf than mature cows – often about 80 to 100 days. Both first-calf heifers and mature cows require additional days after calving to resume cycling if they are less than a body condition score of 5 on a 9-point scale. Once cows begin lactating, it is very difficult to add body condition; therefore, if cows are thin during gestation, you must adjust their diet so that weight is added before they calve. Careful attention to body condition during late pregnancy is critical so that necessary ration changes such as giving access to high-quality forage or lower-quality forage supplemented to meet protein and energy needs can be accomplished to guarantee good body condition at calving.
Because heifers take longer to resume fertile cycles after their first calf than after later pregnancies, it is nearly impossible for a group of heifers to have an average calving date for their second calves as three-year olds that is as early as the average date for their first calving as two-year olds. This problem can be addressed by scheduling the heifer breeding season so that heifers will calve before the cows begin calving; or at the latest, during the first few weeks of the calving season. In order to make sure that heifers reach puberty prior to their first breeding season, herd managers should measure body weight periodically from weaning to the start of breeding and make adjustments to the diet to ensure that an adequate number of heifers in the replacement pool have reached the herd-specific target weight for puberty (usually 55 to 65% of mature weight). Additionally, prior to the breeding season, a veterinarian can palpate the reproductive tract of all potential replacement heifers to determine if nearly all the heifers have palpable corpus luteum (CL) and a mature uterus indicating sufficient maturity to become pregnant to an A.I. mating or early in the breeding season. If estrous synchronization and A.I. are utilized, palpating reproductive tracts to ensure that nearly all the heifers are cycling before the time and expense of synchronization and A.I. are sunk will help protect against disappointing results.
Bulls must be able to breed all the cows that are in heat each day of the breeding season in order to achieve good reproductive efficiency. It is critical that bulls be examined for breeding soundness before the start of the breeding season. A complete breeding soundness examination will evaluate the bulls’ health, ability to move freely, and semen quality. Bulls that fail any of these criteria should not be used for breeding. In addition to a breeding soundness examination before the start of the breeding season, bulls must be observed closely the first few days of the breeding season. Some bulls have problems with movement, mounting, or breeding that are difficult or impossible to detect in a squeeze chute or small pen. Therefore, even bulls that pass a breeding soundness must be evaluated closely in the breeding pasture to make sure that they successfully breed the cows showing heat. Both bulls and cows should be examined throughout the breeding season to make sure that fewer cows are showing heat as the breeding season progresses indicating successful establishment of pregnancy, and that bulls do not develop any visible problems with feet, legs, penis, testicles, or body condition that impair breeding performance.
A number of diseases can cause cows to fail to become pregnant or to lose the pregnancy before a live calf is born. Different diseases that cause pregnancy loss act in different ways. Some attack very early in pregnancy, others are more likely to cause problems in mid- or late-pregnancy. Some are spread to pregnant cows from other cows, calves, or bulls in the same herd or from cattle in adjacent pastures. Other diseases expose the herd through contaminated feed. A plan to use available vaccines, isolation of the herd away from high-risk cattle, proper feed harvesting, storage and delivery, and appropriate use of diagnostic tests should be developed with your veterinarian to address the most important risks to your herd.
Herds that have excellent reproductive efficiency do so because herd managers and their veterinarians and other advisors address many details that affect heifer development, cow body condition, bull fertility, and disease control. The result of a reproduction management strategy that prioritizes all these aspects of animal husbandry is a herd that has early calving replacement heifers, cows that enter the calving season in good body condition, nearly all the cows resuming fertile cycles within the first 21 days of the breeding season, bulls that are fertile and able to breed all the cows that come into heat, and little or no loss of pregnancies due to disease.
