Reproduction · Postpartum care · Litter health
A painful mammary gland is not always infected, and a positive culture does not by itself diagnose mastitis. Decisions integrate the dam, each gland, the litter, cytology and a properly interpreted sample.
Key points. Mastitis ranges from local inflammation to severe infection with abscessation, necrosis, maternal sepsis and neonatal disease. Examine every gland and every neonate: a restless litter, poor weight gain or neonatal deterioration may precede obvious maternal illness. Heat, pain, induration, purulent or bloody secretion, purple/black skin, fever or depression require prompt veterinary assessment. Cytology, culture, ultrasonography and blood tests are selected by severity; no single result replaces the clinical examination.
General information for breeders and owners. No antibiotic, anti-inflammatory, drainage or dose protocol is provided here. Septic and gangrenous disease are veterinary emergencies.
1. Congestion, inflammation, infection, abscess or gangrene are not interchangeable
The mammary gland changes rapidly postpartum. Milk stasis may cause a tense, uncomfortable gland without established infection. Conversely, early infection may involve one gland and produce subtle maternal signs while the neonates become unsettled or fail to gain weight.
| Condition | Dominant clues | How it is supported | Main risk |
|---|---|---|---|
| Congestion / stasis | Full tense gland after abrupt weaning, a small litter or uneven nursing. | Examination, evolution and no concordant evidence of infection. | Pain, impaired milk release and possible secondary entry point. |
| Clinical mastitis | Heat, pain, swelling, induration, altered milk, sometimes systemic illness. | Clinical concordance, cytology and culture when indicated. | Local spread, maternal sepsis and insufficient neonatal intake. |
| Intramammary infection without overt signs | Positive culture with little or no clinical abnormality. | Good sampling and contextual or repeated interpretation. | Overdiagnosis and unnecessary antimicrobials. |
| Abscess | Fluctuant painful mass, fluid cavity, sometimes a draining tract. | Examination and ultrasound; deep sample during drainage. | Rupture, contamination, pain and tissue loss. |
| Gangrene / necrosis | Dark, cold or severely painful skin, rapid demarcation, systemic illness. | Urgent clinical and surgical diagnosis. | Sepsis, shock, gland loss and death. |
Key point: milk colour, pH or bacterial growth alone cannot determine whether a gland is infected.
2. Signs and associated factors: observe the dam, glands and litter
In a retrospective cohort of two guide-dog populations totalling 3,076 whelpings, clinical mastitis was recorded in 13.2%, on average around postpartum day 17. Litters of at least nine puppies and mammary congestion were associated with greater risk. These figures describe two monitored colonies and are not a universal prevalence for every breed or breeding setting.
Plausible contributors include milk stasis, teat trauma from claws or teeth, poor hygiene, skin lesions, abrupt cessation of nursing and concurrent postpartum disease. Haematogenous spread is possible in uterine or systemic disease but should not be assumed without a work-up.
| Target | Possible early signs | Severity signs | Action |
|---|---|---|---|
| Dam | Discomfort, reduced appetite, agitation when neonates approach. | Depression, fever/hypothermia, tachypnoea, dehydration or shock. | Urgent examination and stabilisation. |
| Gland | Asymmetry, heat, pain, oedema or local induration. | Fluctuation, ulceration, purple/black skin, rapid spread. | Imaging/sampling and surgical assessment. |
| Secretion | Different appearance between glands. | Pus, blood, abnormal odour or debris from a diseased gland. | Do not feed that secretion; veterinary sample. |
| Litter | Restlessness, prolonged nursing, uneven weight gains. | Weakness, coldness, static/falling weight, digestive/respiratory signs. | Examine individuals; do not wait for overt maternal illness. |
3. A three-part examination: the whole dam, every gland and every neonate
The history includes birth and medication, caesarean section, onset, appetite, vaginal discharge, nursing, recent weaning/removal and each neonate’s weight trajectory. General examination assesses pain, hydration, perfusion, temperature, uterine disease and other infectious foci.
Inspect and palpate each gland and teat separately, including unused glands. Compare temperature, texture, pain, skin and secretion. Weigh and examine each neonate for temperature, hydration, mouth/palate, suck, breathing, abdomen, faeces and alertness.
Potential trap: an apparently well dam does not exclude mammary disease; sick neonates do not prove that milk caused their infection.
4. Cytology, culture, ultrasound and blood tests: answer a defined question
Milk for cytology and culture is sampled gland by gland with aseptic preparation and, when the dam’s condition allows, before antimicrobials. Secretions from different teats should not be pooled. With an abscess, a deep sample during drainage may be more informative than a surface swab.
Cytology looks for neutrophilic inflammation, cell degeneration and intracellular bacteria. Neutrophil proportions vary with lactation and stasis, and there is no universal cut-off for every bitch or queen. Culture identifies an organism and informs susceptibility testing, but it must match the clinical picture.
Among 11 healthy bitches sampled twice, 180 of 210 milk samples grew bacteria despite no mastitis. Another study of 87 bitches found positive culture in 93.2% of 162 samples from healthy glands, clinical mastitis and so-called subclinical disease. Methods and definitions differed; the robust conclusion is that growth does not equal disease.
| Test | Useful question | Interpret | Limitation |
|---|---|---|---|
| Milk cytology | Compatible septic inflammation? Phagocytosed bacteria? | Degenerate neutrophils, intracellular bacteria, haemorrhage. | Stasis/lactation alter cells; no universal cut-off. |
| Culture + susceptibility | Agent in severe, recurrent or refractory disease? | Species, abundance, purity, resistance and clinical concordance. | Colonisation/contamination; false negative after treatment. |
| Ultrasound | Collection, abscess, necrosis or discordant gland? | Architecture, cavity, content and extent. | No universal ultrasound threshold; operator dependent. |
| CBC/chemistry/CRP | Systemic inflammation, dehydration or organ dysfunction? | Leukocytosis/leukopenia, perfusion, metabolism and inflammation. | Non-specific; milk CRP remains an investigated marker. |
| Uterus/other foci | Metritis, retention, sepsis or concurrent disease? | Examination, discharge, ultrasound and selected samples. | Normal postpartum appearance changes over time. |
5. Make the dam and litter safe before improvising treatment
The dam and litter are interdependent patients. Severe maternal illness may require hospitalisation, fluids, analgesia, rapid sampling and surgery. Each neonate needs appropriate warmth, individual weighing and a feeding route matched to its swallowing reflex.
| Situation | Priority | Avoid |
|---|---|---|
| Unstable dam / suspected sepsis | Urgent transport, rational warming, IV access and veterinary stabilisation. | Waiting for culture without supportive care. |
| Purulent, open or necrotic gland | Prevent nursing from that gland, protect the wound, obtain surgical advice. | Puncturing, forceful expression or irritant topical products. |
| Stable litter, uncertain intake | Individual weights, observed feeds and targeted milk replacement. | Removing the entire litter without a feeding and monitoring plan. |
| Cold, weak or dyspnoeic neonate | Assess and stabilise before feeding; trained technique. | Force-feeding and aspiration. |
| Sample required | Collect properly before antibiotics if vital care is not delayed. | Using a surface wound swab as a deep-tissue result. |
6. Treatment principles: stabilise, control the focus and preserve viable tissue
Management depends on stage. Non-infected congestion, septic mastitis, a closed abscess and a gangrenous gland are not treated alike. Priorities are systemic stabilisation, lactation-compatible analgesia, source control, drainage of a collection when indicated and rational antimicrobial treatment for infectious disease.
Antimicrobial selection considers severity, likely organism, samples, local resistance, tissue penetration, renal/hepatic function and neonatal exposure through milk. A 2025 study of 39 bitches and 156 samples documented resistance and biofilm determinants in staphylococci; it supports susceptibility testing but does not create a universal empirical regimen.
Necrosis, abscessation or poor response may require debridement, drainage or excision. These are not home procedures. Compresses, massage and milk expression may worsen pain, spread or tissue damage when used without a diagnosis.
7. May puppies or kittens continue nursing? Decide gland by gland and treatment by treatment
Automatic separation is not always justified, but neither is continued nursing without assessment. Consider maternal/neonatal status, number and location of affected glands, secretion, open wounds or drains, suspected agent, medication and the ability to feed the litter safely by another route.
The link between milk bacteria and neonatal sepsis is not automatic. In a retrospective study of 46 bitches and 33 septic puppies, matching organisms were mainly Escherichia coli, Klebsiella pneumoniae or beta-haemolytic streptococci in four dam–litter situations. The authors considered milk unlikely to be the primary cause in most cases. This older retrospective study neither trivialises mastitis nor attributes every neonatal illness to milk.
| Situation | Affected gland | Other glands | Monitor |
|---|---|---|---|
| Confirmed non-septic congestion | Nursing may sometimes continue or be reorganised under supervision. | Usually usable if healthy. | Pain, local evolution and individual weights. |
| Purulent/bloody secretion or open abscess | Exclude until veterinary decision. | Individual decision after examination. | Contamination, wound, total intake and neonatal signs. |
| Gangrene, drain or surgery | No. | Depends on maternal status, medication and wound protection. | Hospital care, replacement feeding and hygiene. |
| Systemically ill dam | Often interrupted during stabilisation. | Reassess after response and treatment compatibility. | Temperature, perfusion, appetite, lactation and litter. |
| Sick neonates | Changing gland alone is not enough. | Examine each neonate first. | Temperature, weight, hydration, digestion, breathing and sepsis. |
8. Close monitoring: extension, relapse and neonatal failure
Improvement is more than lower temperature. Record comfort, appetite, hydration, every gland’s size/texture, necrotic margins, discharge, wounds and maternal behaviour. Another gland can become involved after treatment starts.
| Parameter | Expected improvement | Alert | Response |
|---|---|---|---|
| General status | Appetite, comfort, temperature and hydration normalise. | Hypothermia, persistent fever, tachypnoea or weakness. | Urgent reassessment and systemic work-up. |
| Gland | Pain/oedema decrease with no new dark area. | Spread, fluctuation, necrosis, odour or dehiscence. | Repeat imaging/sampling and surgical review. |
| Litter | Effective feeds, quiet sleep, rising weight trajectories. | Any neonate stalls, cools or develops digestive/respiratory signs. | Individual examination and feeding audit. |
| Microbiology | Response matches organism and susceptibility. | Resistance, discordant culture or recurrence. | Review sample, focus, adherence and differentials. |
| Wound/drain | Viable tissue, controlled discharge, decreasing pain. | Obstruction, contamination, self-trauma or tissue loss. | Veterinary care; no improvised manipulation. |
9. Prevent disease without trying to sterilise lactation
- Before birth: assess skin, teeth, reproductive tract and body condition; prepare quiet washable bedding.
- Daily: gently inspect every gland and teat, and record appetite, behaviour and individual neonatal weights.
- Distribute nursing: watch unused glands and large litters without excessive handling.
- Reduce trauma: rational claw care and clean bedding; avoid repeated harsh antiseptics on teats.
- At weaning: use a gradual transition where possible and monitor congestion.
- After recurrence: review obstetric history, cultures, environment and practice rather than treating every future dam prophylactically.
Screening culture of normal-looking milk does not automatically justify treatment. Healthy-milk data show frequent culturable bacteria; the goal is to prevent clinical disease, not make every sample sterile.
10. Practical questions
Does a hot gland always mean infection?
No. Congestion and non-septic inflammation can cause heat and tension. Pain, systemic status, secretion, cytology and progression refine the diagnosis.
Does a positive culture prove mastitis?
No. Bacteria are often cultured from healthy canine milk. Sampling quality, abundance, purity, cytology and clinical signs are essential.
Must all milk be discarded if one gland is affected?
Not automatically. Decide gland by gland according to the lesion, maternal condition, treatment and litter safety.
May I massage or empty a painful gland?
Not without a diagnosis. Gentle handling may help selected stasis cases, but forceful expression can worsen an abscess, necrosis or pain.
Can neonates become ill before the dam?
Yes. Restlessness, poor gain or weakness may be the first sign. They need their own examination because the cause is not always mammary.
Does ultrasound confirm mastitis?
No. It localises collections and describes architecture, but is interpreted with examination, cytology and microbiology.
Does recurrence mean the dam must be removed from breeding?
Not from that fact alone. Review obstetric factors, stasis, lesions, persistent organisms, resistance, environment and general health before an individual reproductive decision.
A painful dam or deteriorating litter
A targeted work-up is safer than empirical treatment
Dr Xavier Lévy can coordinate mammary and postpartum examination, ultrasonography, cytology/culture and neonatal weight monitoring with the primary veterinarian, at CRECS near Toulouse or Bordeaux Sud. International FR/EN remote support is available within the applicable regulatory framework.
11. Sources and strength of evidence
Personal sources consulted exclusively for VetReproduction: Dr Xavier Lévy, Post-partum diseases: metritis, mastitis, SIPS, placental retention, metrorragy and milk insufficiency (complete July 2023 lecture); personal clinical sheet Septic mastitis. Historic doses, detailed drainage techniques and automatic weaning rules were excluded.
- Lection J et al. Incidence and risk factors for canine mastitis and metritis in two guide dog populations. Anim Reprod Sci. 2021;231:106802. Retrospective cohort, 3,076 whelpings in two colonies; association is not causation. PMID 34280749.
- Schäfer-Somi S et al. Bacteriological status of canine milk and septicaemia in neonatal puppies. J Vet Med B. 2003;50:343–346. Retrospective: 46 bitches and 33 septic puppies; limited matching. PMID 14535933.
- Ververidis HN et al. Experimental staphylococcal mastitis in bitches. Vet Microbiol. 2007;124:95–106. Experimental model in six bitches; not directly transferable to all spontaneous disease. PMID 17481831.
- Vasiu I et al. Milk C-reactive protein in canine mastitis. Vet Immunol Immunopathol. 2017;186:41–44. Biomarker study, not a universal standalone threshold. PMID 28413048.
- Vasiu I et al. Aerobic Isolates from Gestational and Non-Gestational Lactating Bitches. Animals. 2021;11:3259. 87 bitches/162 samples with heterogeneous clinical groups. PMID 34827990.
- Mila H et al. Bacteria in Normal Canine Milk Analyzed by Blood Agar Medium. Animals. 2023;13:2206. Eleven healthy bitches/210 samples; frequent growth, small cohort. PMID 37444004.
- Characterization of Staphylococcus aureus and other mastitis-causing pathogens isolated from canine milk. Res Vet Sci. 2025;196:105907. 39 bitches/156 samples; resistance and biofilm data, no universal protocol. PMID 41005215.
- Vasiu I et al. A systematic review of mammary gland inflammations in queens. Anim Reprod Sci. 2023;256:107318. Systematic review documenting sparse feline-specific evidence. PMID 37586155.
Critical reading. The strongest canine evidence remains mostly observational, microbiological or experimental. Feline evidence is sparse and case-dominated. Practice therefore depends on clinical concordance, source control, litter safety and close reassessment.