# Dairy Heifer Breeding Readiness ## Key Takeaways - **Growth Targets are Paramount:** Dairy heifers must achieve 55-60% of their mature body weight before breeding, a metric more critical than age alone, to mitigate dystocia risk and ensure future reproductive performance. Consistent 30-day weight monitoring is essential. - **Health Status is a Prerequisite:** Absence of chronic diseases, pelvic injuries, and reproductive tract pathology is vital; pre-breeding veterinary examinations, including reproductive tract assessment and screening for pathogens like Bovine Viral Diarrhea Virus (BVDV), are recommended. - **Estrus Detection Requires High Accuracy:** Detecting standing heat with at least 95% accuracy over two cycles is necessary, utilizing a combination of visual observation (twice daily for 20+ minutes), tail chalk, or activity monitors to confirm cyclicity before insemination. - **Integrated Breeding Plans are Essential:** Coordinated plans must synchronize insemination timing, sire selection, and calving seasons, aligning with herd goals and considering seasonal effects on conception rates to avoid heat stress. - **Nutritional and Environmental Factors Influence Fertility:** Balanced rations, adequate water access, and stress-free housing are critical for consistent growth and estrous cyclicity; over- or under-conditioning heifers negatively impacts fertility and calving ease. - **Systematic Record-Keeping is Foundational:** Comprehensive individual records tracking growth, health events, vaccination status, and breeding cycles are indispensable for evaluating performance, identifying failure patterns, and enabling targeted veterinary interventions. --- Dairy heifer breeding readiness is established when an individual animal meets defined growth targets, has a documented health history free of reproductive impairments, displays consistent estrus behavior, and is enrolled in a coordinated breeding plan that aligns with herd goals for age at first calving. ## At a Glance | Component | Objective | Primary Reference | |-----------|-----------|------------------| | Growth | Achieve 55,60% of mature body weight before breeding | [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) | | Health history | Confirm absence of chronic disease, pelvic injury, or reproductive tract pathology | [Merck Veterinary Manual](https://www.merckvetmanual.com/) | | Estrus observation | Detect standing heat with ≥95% accuracy over at least two cycles | [Accuracy of Predicting Stages of Bovine Estrous Cycle by Gross Appearance of the Corpus Luteum](https://api.elsevier.com/content/abstract/scopus_id/0018882655) | | Breeding plan coordination | Synchronize timing of insemination, sire selection, and calving season | [FAO Animal Production and Health](https://www.fao.org/animal-production/en/) | ## System Context: Heifer Development and Reproduction Dairy heifer rearing represents a substantial investment in replacement stock. The interval between birth and first calving directly influences lifetime productivity, culling risk, and feed costs. [Interrelationships Between Energy Balance and Postpartum Reproductive Function in Dairy Cattle](https://api.elsevier.com/content/abstract/scopus_id/0024636377) established that nutritional status before and after puberty determines subsequent fertility. Growth rate, in particular, affects the onset of cyclicity and the ability to maintain pregnancy. Heifers that achieve inadequate body weight at breeding are at elevated risk for dystocia, which in turn impairs future reproductive performance. [Prevalence and risk factors for dystocia in dairy cattle: A review](https://api.elsevier.com/content/abstract/scopus_id/40649119288) confirmed that heifer body condition and pelvic dimensions are modifiable determinants of calving ease. The [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) emphasizes that breeding animals should be screened for infectious diseases that compromise reproductive outcomes, including [bovine viral diarrhea virus](/knowledge/viruses/livestock-viruses/bovine-viral-diarrhea-virus) and infectious bovine rhinotracheitis. A structured health protocol before breeding reduces the probability of embryonic loss, which is a significant contributor to reproductive failure in dairy heifers according to [Embryonic and Early Foetal Losses in Cattle and Other Ruminants](https://api.elsevier.com/content/abstract/scopus_id/56549108509). ## Planning Decisions for Breeding Readiness ### Target Age and Body Weight Breeding should not commence before 13 months of age in most Holstein-based herds, although breed and management system influence this threshold. The critical metric is body weight relative to mature size instead of absolute age. [Invited review: Effects of milk ration on solid feed intake, weaning, and performance in dairy heifers](https://api.elsevier.com/content/abstract/scopus_id/79951709776) demonstrated that early nutrition programs affect growth trajectory and subsequent reproductive capacity. Weight measurement every 30 days, using calibrated scales, provides data to determine whether a heifer is on track to reach 55,60% of predicted mature body weight by the intended breeding date. ### Health History Documentation A comprehensive health record must include vaccination status, parasite control measures, and any treatments for pneumonia, diarrhea, or lameness. [PubMed record 42431447](https://pubmed.ncbi.nlm.nih.gov/42431447/) reported that respiratory disease in preweaned calves reduces the likelihood of timely puberty. Similarly, [PubMed record 42398853](https://pubmed.ncbi.nlm.nih.gov/42398853/) linked early-life metabolic stress to delayed first ovulation. Veterinary examination of the reproductive tract, including transrectal ultrasonography if available, should be performed at least 30 days before planned breeding to detect ovarian abnormalities, uterine adhesions, or vaginal discharges. ## Core Management Framework ### Growth Monitoring and Nutritional Adjustment A consistent feeding program that delivers a balanced ration with adequate energy, protein, minerals, and vitamins is essential. [Body condition scoring](/knowledge/animal-farming/farm-management/body-condition-scoring-a-tool-for-feed-management) on a 1,5 scale every two weeks supplements weight data. Heifers falling below the target growth curve require ration reformulation or increased feed intake, also postponement of breeding. [USDA APHIS Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) resources note that subclinical deficiencies in selenium, copper, and zinc impair immune function and may contribute to early embryonic death. ### Estrus Detection and Cycle Confirmation Standing heat is the primary behavioral sign of estrus. Observation periods of at least 20 minutes twice daily, ideally early morning and late evening, yield detection rates above 90% when combined with secondary aids such as tail chalk or activity monitors. [PubMed record 42398722](https://pubmed.ncbi.nlm.nih.gov/42398722/) demonstrated that mounting activity peaks during cooler hours, making environmental timing relevant. At least two confirmed estrous cycles should be recorded before insemination to confirm cyclicity and allow scheduling of timed artificial insemination protocols if used. ### Breeding Plan Coordination The breeding plan must be written and shared with all personnel involved. It should specify the target first-service date, acceptable sires, semen handling procedures, and the protocol for rebreeding after a nonreturn event. [PubMed record 42398704](https://pubmed.ncbi.nlm.nih.gov/42398704/) found that seasonal effects on conception rates are more pronounced in heifers than in cows, indicating that breeding season should be planned to avoid heat stress. Veterinarians and herd managers coordinate these decisions based on calving interval goals, facility capacity, and market timing. Uncertainty about any parameter,whether growth data, estrus records, or health background,should prompt deferral of breeding until the missing information is obtained and reviewed by a qualified professional. ## Facilities and Environment Housing systems for replacement heifers must support steady growth without imposing chronic stress. The [Food and Agriculture Organization Animal Production and Health guidance](https://www.fao.org/animal-production/en/) emphasizes that loose,housing with adequate resting area, dry bedding, and sufficient bunk space reduces competition and allows normal estrous expression. Overcrowding inhibits mounting behavior and can delay detection of standing heat. For breeding,age heifers, a separate pen near the milking herd or a dedicated observation area facilitates heat checks without disturbing the lactation group. Non,slip flooring underfoot is critical because heifers are more active during proestrus and estrus, and falls or foot injuries can suppress cyclicity. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) notes that poor footing, muddy lots, or excessive heat load contribute to silent heats or anestrus. Ventilation should prevent ammonia buildup, which irritates mucosa and may reduce feed intake. If estrus synchronization is used, the environment must allow safe handling for injections and artificial insemination (AI) without creating aversion to the breeding barn. ## Nutrition and Water Growth rate and age at puberty are directly shaped by energy and protein supply during the pre,weaning and growing phases. Research from [PubMed record 42398722](https://pubmed.ncbi.nlm.nih.gov/42398722/) and [PubMed record 42398704](https://pubmed.ncbi.nlm.nih.gov/42398704/) indicates that excessive milk feeding before weaning accelerates weight gain but can reduce starter intake and delay rumen development, potentially compromising later growth consistency. A controlled milk ration, as reviewed in the Elsevier abstract *Invited review: Effects of milk ration on solid feed intake, weaning, and performance in dairy heifers* [link](https://api.elsevier.com/content/abstract/scopus_id/79951709776), supports a smoother transition to forage,based diets and more uniform body condition at breeding. After weaning, energy balance remains central to reproductive function. The Elsevier abstract *Interrelationships Between Energy Balance and Postpartum Reproductive Function in Dairy Cattle* [link](https://api.elsevier.com/content/abstract/scopus_id/0024636377) demonstrates that even moderate negative energy balance delays luteal activity and reduces conception rates. For nulliparous heifers, body condition score (BCS) should be monitored every two to three weeks, overconditioned heifers (BCS > 3.75 on a 5,point scale) are more prone to dystocia and metabolic disorders that postpone breeding. Conversely, underfeeding prolongs the prepubertal period. Clean, fresh water must be available ad libitum, because even short,term water restriction depresses dry matter intake and disrupts estrous cyclicity. The [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) reports that water space of 5 cm per head or less in group pens is associated with increased competition and reduced water consumption, particularly during hot weather. ## Production,Stage Decisions The decision to breed a heifer rests on achieving a target body weight,generally 55 to 60 percent of mature herd weight,instead of a fixed age. Data from [PubMed record 42431447](https://pubmed.ncbi.nlm.nih.gov/42431447/) show that heifers bred at lighter weights have longer intervals to conception and lower first,service pregnancy rates. Using age as the sole criterion introduces risk because growth paths vary with genetics, nutrition, and health history. Estrus synchronization protocols can concentrate breeding efforts, but their success depends on cyclicity status. The [World Organisation for Animal Health (WOAH) Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) includes recommendations for ensuring that hormonal treatments are used in cycling animals to avoid wasted doses and poor fertility. Before any synchronization program, a veterinary or reproductive technician should confirm ovarian activity via palpation or ultrasonography. Heifers that have not shown estrus by 14 to 16 months of age warrant a targeted examination for freemartinism, ovarian hypoplasia, or chronic infection. The approach to first breeding also must consider expected calving ease: heifers bred at smaller frame sizes or to sires with high calving,ease scores experience fewer dystocia events (Elsevier abstract *Prevalence and risk factors for dystocia in dairy cattle: A review* [link](https://api.elsevier.com/content/abstract/scopus_id/40649119288)). Breeding too early, before pelvic area and body mass are adequate, elevates the incidence of stillbirth and postpartum complications that compromise future lactation. ## Records Systematic record,keeping is essential for evaluating heifer development and breeding efficiency. Individual identification linked to birth date, weaning weight, BCS at six,month intervals, vaccination history, and all health events allows managers to calculate age,at,puberty and growth velocity. The [USDA Animal and Plant Health Inspection Service (APHIS) Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) guidance recommends maintaining a separate breeding log that captures dates of observed estrus, insemination, sire used, and results of pregnancy diagnosis. Without these records, it is difficult to detect patterns such as anestrus clusters, repeat breeders, or seasonal dips in conception. Electronic herd management software can generate alerts when a heifer misses an expected heat or exceeds a target breeding window. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) notes that incomplete or inaccurate records are a common obstacle to diagnosing poor reproductive performance at the herd level. When veterinary consultation occurs, a complete history reduces guesswork and enables more focused diagnostics, such as uterine cytology or blood progesterone assays. ## Welfare Heifer welfare directly influences reproductive readiness. Chronic stress from crowding, pain from lameness, or social instability suppresses gonadotropin,releasing hormone pulsatility and delays puberty. A study from [PubMed record 42353467](https://pubmed.ncbi.nlm.nih.gov/42353467/) underlines the role of environmental enrichment and consistent daily routines in maintaining normal estrous behavior. Lameness, often caused by inadequate foot,trimming schedules or abrasive concrete, reduces mounting activity and can shorten the duration of estrus, making heat detection less reliable. Body condition extremes are both welfare and production concerns: overconditioned heifers are at higher risk for dystocia and subsequent metritis, while thin heifers suffer energy deficiency that impairs immune function. The [FAO Animal Production and Health](https://www.fao.org/animal-production/en/) resources advise regular mobility scoring and prompt treatment of injuries. For group,housed heifers, provide at least one feeding space per four animals and one lying space per animal to minimize aggression. If estrus synchronization involves repeated handling, low,stress techniques reduce cortisol spikes and improve conception outcomes. The accuracy of predicting stages of the bovine estrous cycle by gross appearance of the corpus luteum (Elsevier abstract [link](https://api.elsevier.com/content/abstract/scopus_id/0018882655)) highlights that skilled palpators can stage the cycle with fair reliability, but less experience may lead to misclassification and unnecessary interventions. Professional training and periodic proficiency checks are therefore welfare and economic safeguards. ## Worker and [Food Safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention) Personnel responsible for heat detection, AI, and health treatments must be trained in proper injection sites, needle disposal, and withdrawal times if any medications are used. Although replacement heifers do not contribute milk at breeding, residues from hormone implants, antibiotics, or anti,inflammatories can accumulate if withdrawal periods are ignored, and safety intervals should be documented. The [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) includes standards for biosecurity when breeding animals are moved between facilities. Workers should use dedicated clothing and footbaths when entering heifer pens to prevent introduction of pathogens that cause abortion, such as *Neospora caninum* or *Bovine viral diarrhea virus*. A written protocol for estrus detection (e.g., twice,daily visual observation for 20 minutes, plus activity monitors) reduces reliance on memory and ensures consistency. If tail,painting or mount,detection patches are used, workers must replace them at the correct intervals and record when they are rubbed. The [USDA APHIS Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) resource emphasizes that proper biosecurity and record,keeping also protect worker health when handling reproductive tracts or fecal samples for pregnancy diagnosis. ## Failure Patterns Common failure patterns in heifer breeding programs include suboptimal growth rate, prolonged anestrus, poor estrus expression, and embryonic loss. The Elsevier abstract *Embryonic and Early Foetal Losses in Cattle and Other Ruminants* [link](https://api.elsevier.com/content/abstract/scopus_id/56549108509) reports that early embryonic mortality can account for 20 to 40 percent of pregnancies in cattle, with nutritional deficits, heat stress, and uterine infection as primary contributors. Heifers that conceive but fail to maintain pregnancy often return to estrus at irregular intervals, complicating next,breeding decisions. Another pattern is the onset of puberty beyond 14 months, which is frequently linked to insufficient energy intake during the growing period or chronic subclinical disease (e.g., persistently infected BVDV animals). The [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) surveys indicate that farms with no systematic health monitoring for heifers have higher culling rates due to reproductive failure. Dystocia in first,calf heifers is a recurring problem that reduces subsequent reproductive performance and leads to involuntary culling. The dystocia review [link](https://api.elsevier.com/content/abstract/scopus_id/40649119288) identifies calf birth weight, heifer pelvic area, and dam body condition as key risk factors that can be managed through sire selection and nutrition. ## Practical Monitoring Practical monitoring of heifer breeding readiness should be embedded in weekly or bi,weekly routines. Weight,scales or heart,girth tapes allow tracking of growth against targets. Combine this with BCS scoring every 30 days to detect deviations early. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) recommends that heifers failing to reach target weight by 12 months of age receive a veterinary work,up including fecal egg count, blood analysis for trace minerals, and evaluation of feeding management. Estrus detection aids,activity collars, pressure,sensitive patches, or automated video systems,increase sensitivity, but their output must be verified by visual observation to avoid false positives. Any heifer inseminated twice without confirmation of conception should undergo pregnancy diagnosis and, if open, a reproductive examination. The [USDA APHIS Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) materials stress that timely veterinary escalation is warranted when more than 15 percent of eligible heifers fail to show estrus by 14 months or when first,service conception drops below 55 percent. In such cases, review of the whole system,nutrition, housing, health records, synchronization protocols,is necessary instead of a single,cause explanation. Professional veterinary consultation should include evaluation of the corpus luteum stage at breeding, uterine health, and bull fertility if natural service is used. With consistent monitoring and prompt corrective action, most heifer breeding programs can achieve acceptable pregnancy rates within the first three weeks of the breeding period. ## 2. Growth and Development Benchmarks ### 2.1 Target Body Weight at Breeding Attaining a minimum of 55 to 60 percent of mature body weight before first breeding is a widely accepted commercial target. Heifers bred below this threshold experience higher calving difficulty and reduced first-lactation milk yield. Weighing heifers individually or by cohort every 30 days allows producers to monitor progress toward the target. Frame score, measured via hip height, provides a secondary check for skeletal maturity. ### 2.2 Age at Puberty and First Estrus Puberty in Holstein heifers typically occurs between 8 and 12 months of age, but onset is influenced by breed, nutrition, and season. Delayed puberty increases rearing costs and reduces lifetime productivity. Producers should confirm estrous cycling before initiating a breeding program. Observation of standing estrus, use of activity monitors, or detection patches can verify cyclicity. ### 2.3 Body Condition Scoring for Breeding Body condition score (BCS) at breeding should fall between 3.0 and 3.5 on a 1-to-5 scale. Heifers with a BCS below 3.0 are under-conditioned and may have reduced conception rates. Those above 3.5 risk metabolic disorders and dystocia. Scoring every three to four weeks enables early identification of animals needing ration adjustment. ## 3. Estrous Detection and Synchronization ### 3.1 Visual Observation Protocols Standing estrus lasting 6 to 18 hours is the most reliable sign of receptivity. Observation sessions should occur at least twice daily for 20 to 30 minutes each, ideally during times of low activity in the barn. Tail chalking, chin-ball markers, or pressure-activated mount detectors can supplement visual checks. ### 3.2 Automated Detection Systems Activity collars and pedometers measure step count and rumination behavior, increased locomotion and decreased rumination correlate with estrus. Automated systems provide continuous monitoring and alert producers when a heifer exceeds preset thresholds. These systems reduce labor but require regular calibration and data review. ### 3.3 Synchronization Program Considerations Prostaglandin-based protocols, such as a single injection followed by fixed-time artificial insemination, can compress the breeding window. Heifers must have a palpable corpus luteum for prostaglandin to be effective. Combination protocols using gonadotropin-releasing hormone and prostaglandin allow timed insemination without daily heat detection. Producers should select a protocol that aligns with their labor availability and facility constraints. ## 4. Nutritional Management for Breeding ### 4.1 Pre-Breeding Ration Formulation Diets should provide 12 to 14 percent crude protein and adequate energy from forage and concentrate to support growth without excessive body fat accumulation. Calcium and phosphorus ratios should be balanced to avoid hypocalcemia risk. Adding organic trace minerals such as zinc and copper may improve immune function and fertility. ### 4.2 Post-Breeding Feeding Adjustments After insemination, maintain the same plane of nutrition for at least 30 days. Drastic changes in energy intake can disrupt the uterine environment and reduce embryo survival. Sudden increases in non-fiber carbohydrates should be avoided. ### 4.3 Water and Forage Access Clean, fresh water must be available at all times. Forage quality should be consistent to prevent ruminal acidosis and subsequent drops in feed intake. Heifers should receive the same forage type they will consume after calving to ease transition. ## 5. Health and Vaccination Protocols ### 5.1 Pre-Breeding Vaccination Schedule Vaccinations against reproductive diseases,including bovine viral diarrhea virus, infectious bovine rhinotracheitis, leptospirosis, and campylobacteriosis,should be completed at least four weeks before breeding. Modified-live vaccines require the heifer to be in good health for an optimal immune response. ### 5.2 Parasite Control and Body Condition Internal and external parasites can impair growth and immune status. Fecal egg counts guide anthelmintic treatment timing. Heifers with high parasite burdens typically have poor BCS and lower conception rates. ### 5.3 Physical Examination Before Breeding Each heifer should pass a pre-breeding examination that includes assessment of vulvar discharge, palpation of the reproductive tract, and evaluation of lameness. Animals with reproductive abnormalities, such as cystic ovaries or uterine adhesions, should be culled before breeding expenses are incurred. ## Frequently Asked Questions **Q1: At what age should a dairy heifer be bred for the first time?** A1: Breed heifers when they reach 55 to 60 percent of mature body weight, which often occurs between 13 and 15 months for Holsteins and slightly older for smaller breeds. Age alone is not a reliable indicator. **Q2: How can I tell if a heifer is in standing heat?** A2: Standing heat is characterized by the heifer standing immobile when mounted by another animal. Additional signs include increased walking, restlessness, and clear mucus from the vulva. Twice-daily observation improves detection. **Q3: What should body condition score be at breeding?** A3: Target a body condition score between 3.0 and 3.5 on a 5-point scale. Heifers below 3.0 have reduced fertility, and those above 3.5 face higher calving difficulty. **Q4: Do I need to use a synchronization protocol for heifers?** A4: Synchronization can reduce labor for heat detection and allow for timed artificial insemination. It is not mandatory but is recommended when labor is limited or when heifers are housed in large groups. **Q5: What vaccinations are essential before breeding?** A5: Core vaccinations include modified-live vaccines for bovine viral diarrhea virus and infectious bovine rhinotracheitis, plus killed vaccines for leptospirosis and campylobacteriosis. Consult a veterinarian for a region-specific plan. **Q6: How long after calving should a heifer be rebred?** A6: The voluntary waiting period is typically 50 to 60 days postpartum, but this decision depends on the heifer’s uterine health, body condition, and milk production. Individualized assessment is advised. **Q7: Can heifers be bred earlier than 13 months of age?** A7: Breeding earlier than 13 months is possible only if the heifer has reached the weight and frame targets defined by the herd’s mature size. Early breeding without adequate size increases calving risk. **Q8: What is the best method for detecting estrus in heifers?** A8: A combination of visual observation twice daily, tail chalk or patches, and automated activity monitoring yields the highest detection rates. No single method is perfect, cross-verification improves reliability. ## Related Farming Guides - [Dairy Cattle Farming Nutrition Housing Health Signals And Herd Management](/knowledge/animal-farming/dairy-cattle/dairy-cattle-farming-nutrition-housing-health-signals-and-herd-management) - [Transition Cow Management From Dry Off To Freshening](/knowledge/animal-farming/dairy-cattle/transition-cow-management-from-dry-off-to-freshening) - [Dairy Calf Colostrum Management](/knowledge/animal-farming/dairy-cattle/dairy-calf-colostrum-management) - [Milking Routine And Parlor Hygiene](/knowledge/animal-farming/dairy-cattle/milking-routine-and-parlor-hygiene) - [Dairy Farm Records That Drive Better Decisions](/knowledge/animal-farming/dairy-cattle/dairy-farm-records-that-drive-better-decisions) ## Related Clinical & Scientific Guides * [Evaluating Feed Additives for Dairy Cow Performance](/knowledge/animal-farming/dairy-cattle/evaluating-feed-additives-for-dairy-cow-performance) * [Dairy Barn Fire Safety: Design and Prevention Measures](/knowledge/animal-farming/dairy-cattle/dairy-barn-fire-safety-design-prevention) * [Dairy Cow Pregnancy Loss Records and Review](/knowledge/animal-farming/dairy-cattle/dairy-cow-pregnancy-loss-records-and-review) ## References and Further Reading - [FAO Animal Production and Health](https://www.fao.org/animal-production/en/) - [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) - [USDA APHIS Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) - [Merck Veterinary Manual](https://www.merckvetmanual.com/) - [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.