{{Short description|Disease of cattle}} {{About|bovine postparturient hypocalcemia|human illness caused by ingestion of milk or meat contaminated by trematol|Milk sickness}} thumb|Typical milk fever posture; cow in sternal recumbency with its head tucked into its flank. '''Milk fever''', '''postparturient hypocalcemia''', or '''parturient paresis''' is a disease, primarily in dairy cattle<ref>{{Cite web|title=Parturient Paresis in Cows - Metabolic Disorders|url=https://www.msdvetmanual.com/metabolic-disorders/disorders-of-calcium-metabolism/parturient-paresis-in-cows|access-date=2020-10-10|website=Veterinary Manual|language=en}}</ref> but also seen in beef cattle and non-bovine domesticated animals,<ref>{{Cite web|title=Parturient Paresis in Sheep and Goats - Metabolic Disorders|url=https://www.msdvetmanual.com/metabolic-disorders/disorders-of-calcium-metabolism/parturient-paresis-in-sheep-and-goats|access-date=2020-10-10|website=Veterinary Manual|language=en}}</ref> characterized by reduced blood calcium levels (hypocalcemia). It occurs following parturition (birth), at onset of lactation, when demand for calcium for colostrum and milk production exceeds the body's ability to mobilize calcium.<ref name="Horst 1997">{{cite journal |last1=Horst |first1=R.L. |last2=Goff |first2=J.P. |last3=Reinhardt |first3=T.A. |last4=Buxton |first4=D.R. |title=Strategies for Preventing Milk Fever in Dairy Cattle |journal=Journal of Dairy Science |date=July 1997 |volume=80 |issue=7 |pages=1269–1280 |doi=10.3168/jds.S0022-0302(97)76056-9 |pmid=9241589 |doi-access=free }}</ref> "Fever" is a misnomer, as the disease generally does not cause elevated body temperature. Milk fever is more commonly seen in older animals (which have reduced ability to mobilize calcium from bone) and in certain breeds (such as Channel Island breeds).<ref name=":1">{{cite journal |last1=DeGaris |first1=Peter J. |last2=Lean |first2=Ian J. |title=Milk fever in dairy cows: A review of pathophysiology and control principles |journal=The Veterinary Journal |date=April 2008 |volume=176 |issue=1 |pages=58–69 |doi=10.1016/j.tvjl.2007.12.029 |pmid=18329301 }}</ref>
== Clinical signs == thumb|Cow lying in sternal recumbency (with sternum in contact with the ground)|219x219px The clinical signs of milk fever can be divided into three distinct stages:
=== Stage 1 === In this stage, cows are mobile but show signs of hypersensitivity and excitability such as restlessness,<ref name=":9">{{Cite web|title=Parturient paresis {{!}} animal disease|url=https://www.britannica.com/science/parturient-paresis|access-date=2020-10-11|website=Encyclopedia Britannica|language=en}}</ref> tremors, ear twitching, head bobbing, and mild ataxia.{{fact|date=August 2025}} If not treated, symptoms usually progress to stage 2.<ref name=":2" />
=== Stage 2 === In this stage, cows can no longer stand and present in sternal recumbency.{{fact|date=August 2025}} Tachycardia, weakened heart contraction and peripheral pulses are observed. Cows appear dull, have dry muzzles, cold extremities, and their body temperature drops. Smooth muscle paralysis can cause bloat, and the inability to urinate or defecate. Cows often tuck their heads into their flanks.<ref name=":2" />
thumb|Cow lying on its side (lateral recumbency)
=== Stage 3 === In this stage, lateral recumbency,<ref>{{cite journal |last1=Oetzel |first1=Garrett K. |title=Parturient Paresis and Hypocalcemia in Ruminant Livestock |journal=Veterinary Clinics of North America: Food Animal Practice |date=July 1988 |volume=4 |issue=2 |pages=351–364 |doi=10.1016/s0749-0720(15)31053-7 |pmid=3264754 }}</ref> muscle flaccidity,<ref name=":9" /> unresponsiveness to stimuli, and loss of consciousness progressing to coma are observed. Heart rate can approach 120 bpm, with peripheral pulses becoming undetectable. If untreated, progression will continue to death.<ref name=":2" />
== Cause == During the dry period (late gestation, non-lactating), dairy cattle have relatively low calcium requirements, with a need to replace approximately 30 g of calcium per day due to utilization for fetal growth and fecal and urinary losses. At birth, the requirement for calcium is greatly increased due to initiation of lactation, when mammary drainage of calcium may exceed 50 g per day.<ref name=":1" /> Due to this large increase in demand for calcium, most cows will experience some degree of hypocalcemia for a short period following birth as the metabolism adjusts to the increased demand. When the mammary drain of plasma calcium causes hypocalcemia severe enough to compromise neuromuscular function, the cow is considered to have clinical milk fever.<ref name="Horst 1997" />
== Mechanism == In normal calcium regulation, a decrease in plasma calcium levels causes the parathyroid glands to secrete parathyroid hormone (PTH), which regulates the activation of vitamin D<sub>3</sub> in the kidney. These two compounds act to increase blood calcium levels by increasing absorption of dietary calcium from the intestine, increasing renal tubular reabsorption of calcium in the kidney, and increasing resorption of calcium from bones.<ref name=":1" />
It has been found that tissue is less responsive to PTH prepartum, compared to postpartum. It is believed that hypocalcemia causing milk fever is due to a lower level of responsiveness of the cow's tissues to circulating parathyroid hormone.<ref name="Horst 1997" />
The resultant decreased plasma calcium causes hyperexcitability of the nervous system and weakened muscle contractions, which result in both tetany and paresis.<ref name=":2">{{Cite web|title = Parturient Paresis in Cows: Disorders of Calcium Metabolism: Merck Veterinary Manual|url = http://www.merckvetmanual.com/mvm/metabolic_disorders/disorders_of_calcium_metabolism/parturient_paresis_in_cows.html|website = www.merckvetmanual.com|access-date = 2015-11-06}}</ref>
==Prevention==
=== Diet === Proper dietary management will prevent most cases of milk fever. This generally involves close attention to mineral and fiber levels in the diet prior to calving, as well as improving cow comfort to eliminate other problems that may interfere with appetite (and so trigger hypocalcemia). General advice is to restrict calcium intake before calving, as this leads to the parathyroid gland stimulating the release of calcium from bones.<ref name=":6" />
=== Calcium salts === A synthetic analogue of 25-hydroxycholecalciferol can be given by injection in the days leading up to calving, although the timing of this prophylaxis makes it difficult to use.<ref name=":6" />
Oral administration of a dose of a calcium salt in a gel has been advised by some veterinarians.<ref>{{cite journal |last1=Haalstra |first1=RT |title=Een bedijfsdiergeneeskundige benadering van de relatie voeding-melkziekte |trans-title=A veterinary approach to the relationship between the diet and milk fever on farms |journal=Tijdschrift voor Diergeneeskunde |date=June 1973 |volume=98 |issue=11 |pages=529–537 |pmid=4736359 |language=nl }}</ref> An orally administered bolus containing a much higher concentration of calcium than the injectable solutions can also be given so long as the cow is standing or sitting up. If the cow is lying 'flat out' then immediate intravenous therapy is required to avoid death.
==Treatment== thumb|Urination and defecation commonly occurring during calcium treatment Treatment generally involves calcium injection by intravenous, intramuscular or subcutaneous routes. Before calcium injection was employed, treatment comprised inflation of the udder using a pneumatic pump. Inflation of the udder worked because the increased pressure created in the udder pushed the calcium in the udder back into the bloodstream of the cow.<ref name=":0">{{cite journal |last1=Niedermeier |first1=R.P. |last2=Smith |first2=Vearl R. |title=Parturient Paresis. IV. The Effect of Udder Inflation upon Blood Levels of Calcium, Magnesium and Phosphorus in Cows with Parturient Paresis |journal=Journal of Dairy Science |date=January 1950 |volume=33 |issue=1 |pages=38–42 |doi=10.3168/jds.S0022-0302(50)91862-5 |doi-access=free }}</ref>
Intravenous calcium, though indicated in many cases, is potentially fatal through "heart blockade", or transient high calcium levels stopping the heart, so should be administered with care. Cows are to be fed jaggery along with the lime water mixture. In unclear cases of downer cows, intravenous calcium injection can lead to diagnosis. The typical reaction will be a generalized tremor of the skeletal muscles, and sometimes cardiac arrhythmia. Defecation, urination and eructation are frequent during the treatment, due to pharmacological effect of calcium on the smooth muscles.
==Prognosis== The prognosis is generally good, even in advanced cases. However, some cows can relapse the following day,<ref name=":0" /> and even a third time the day after.<ref name="LMahin">{{citation |author = Lucien Mahin|title = Observations on diseases of cattle in Morocco|date = 1977–2008}} (unpublished data)</ref> Without treatment, between 60% and 80% of cows usually die,<ref name=":4">{{cite journal |last1=Hibbs |first1=J.W. |title=Milk Fever (Parturient Paresis) in Dairy Cows—A Review |journal=Journal of Dairy Science |date=October 1950 |volume=33 |issue=10 |pages=758–789 |doi=10.3168/jds.s0022-0302(50)91966-7 |doi-access=free }}</ref><ref name=":5" /> although death rates as high as 90% have been recorded.<ref name=":9" />
==History== It is thought that milk fever has existed for a very long time in dairy cattle.<ref name=":3">{{cite journal |last1=Repp |first1=John J. |title=The Schmidt treatment for parturient paralysis |journal=Journal of Comparative Pathology and Therapeutics |date=January 1901 |volume=14 |pages=313–321 |doi=10.1016/S0368-1742(01)80063-1 }}</ref> The first reports in veterinary literature can be traced to around 1793.<ref name=":4" />
=== Early theories === Early treatments involved venesection, but this proved ineffective.<ref name=":6">{{cite journal |last1=Murray |first1=R. D. |last2=Horsfield |first2=J. E. |last3=McCormick |first3=W. D. |last4=Williams |first4=H. J. |last5=Ward |first5=D. |title=Historical and current perspectives on the treatment, control and pathogenesis of milk fever in dairy cattle |journal=Veterinary Record |date=November 2008 |volume=163 |issue=19 |pages=561–565 |doi=10.1136/vr.163.19.561 |pmid=18997185 }}</ref>
==== Potassium iodide ==== In the late 1800s, Jurgens Schmidt proposed the use of an infused solution of potassium iodide for treatment.<ref name=":3" /> A follow-up study of this treatment by Danish veterinarians showed that 90% of cows recovered after use of the treatment,<ref name=":3" /> compared with only 20-40% survival without.<ref name=":4" /><ref name=":5">{{cite journal |last1=Horst |first1=R.L. |last2=Goff |first2=J.P. |last3=Reinhardt |first3=T.A. |last4=Buxton |first4=D.R. |title=Strategies for Preventing Milk Fever in Dairy Cattle |journal=Journal of Dairy Science |date=July 1997 |volume=80 |issue=7 |pages=1269–1280 |doi=10.3168/jds.s0022-0302(97)76056-9 |pmid=9241589 |doi-access=free }}</ref> A study in Iowa showed that 76.5% of cows recovered after use of the treatment.<ref name=":3" /> However, the premise of the Schmidt treatment was misleading, as later veterinarians used water alone to the same success rate.<ref name=":4" />
==== Udder inflation ==== In 1901, Anderson and Evers trialled a treatment of udder inflation with air, which reduced mortality rates to just 1%.<ref name=":4" /><ref name=":7">{{cite thesis |last1=Goings |first1=Richard Lewis |title=Efficacy of a prepartum, calcium-deficient diet in prevention of bovine parturient paresis |date=1973 |doi=10.31274/rtd-180813-2830 |doi-access=free }}{{pn|date=August 2025}}</ref> although with the added complication of mastitis.<ref name=":7" /> Although this was an effective treatment (and is still used as a backup today),<ref name=":0" /> it was not understood at the time why it worked, and remains the source of some debate. Some scientists believed that udder inflation could cause stimulation that then prevents calcium loss.<ref>{{cite journal |last1=Dryerre |first1=Henry |last2=Greig |first2=J Russell |title=Milk Fever: its possible association with derangements in the internal secretions |journal=The Canadian Veterinary Journal |date=July 1985 |volume=26 |issue=7 |pages=224–227 |pmc=1680093 |pmid=17422555 }}</ref> Other scientists suggested that udder inflation prevented milk secretion, reducing calcium loss overall.<ref name=":8">{{cite journal |last1=Petersen |first1=W. E. |last2=Rigor |first2=T. V. |title=Relation of Pressure to Rate and Quality of Milk Secreted. |journal=Experimental Biology and Medicine |date=November 1932 |volume=30 |issue=2 |pages=254–256 |doi=10.3181/00379727-30-6444 }}</ref><ref>{{cite report |last1=Garrison |first1=E. R. |last2=Turner |first2=C. W. |title=The effect of udder irrigation and milking interval on milk secretion |date=February 1936 |series=Research Bulletin 234 |publisher=University of Missouri. Agricultural Experiment Station |hdl=10355/53466 |hdl-access=free }}</ref> This may prevent calcium being taken from the blood plasma.<ref name=":8" />
=== Later theories === The true cause of milk fever was first suggested by Prof John Russell Greig and Henry Dryerre in March 1925,<ref name=":4" /> at the Moredun Research Institute in Scotland.<ref>{{cite magazine|title=Phone call reveals links to Moredun's past|magazine=Moredun Magazine|date=2013|issue=6|page=1|url=http://www.moredun.org.uk/webfm_send/579|archive-url=https://web.archive.org/web/20160821154717/http://www.moredun.org.uk/webfm_send/579 |archive-date=21 August 2016 }}</ref> This idea was later confirmed experimentally by Little and Wright in May 1925.<ref name=":4" /> By 1933, Pulles began treatments with magnesium chloride and calcium chloride, which is the basis for modern pharmaceutical treatments.<ref name=":6" />
== References == {{reflist}}
== External links == * [https://web.archive.org/web/20070221143836/http://www.uky.edu/Ag/AnimalSciences/dairy/extension/nut00046.pdf Prevention of Milk Fever], University of Kentucky * [http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/80302.htm Parturient Paresis in Cows (Milk fever, Hypocalcemia)], The Merck Veterinary Manual
{{Commons category|Hypocalcemia in ruminants}}
Category:Bovine diseases Category:Dairy farming