Do cows produce more milk than it is required for their calves? It seems like cows are able to provide milk all the time (all year around). Is it so? Or do they, like other mammals, produce milk only in ammounts requeired by their offspring?
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asked Feb 19, 2012 at 15:03
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$\begingroup$ milk cows have millenium of selective breeding for milk production. they produce 2-3 times more than normal cows and have crazy sized udders. In the wild, can baby animals risk drinking too much milk? not really! Mammal milk production is normally decided by A/birth and B/the babies appetite and then weaning. $\endgroup$– bandybabboonMar 18, 2019 at 14:27
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3 Answers
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The average domesticated dairy cow produces far more milk than would be required to feed their calf. All cows, wild and domesticated, will only lactate in the period between their calf's birth and weaning. Milk is calf-food, and when there's no calf, there's no evolutionary advantage in producing milk.
On dairy farms, cows are milked twice daily, from spring (when they give birth) until late autumn. This mechanical milking 'fools' the cow into continuing to lactate. When a cow has stopped lactating, they will only start again after giving birth. This means that you can't just start milking a cow and expect to get milk.
Generally farmers milk their cows from spring (birth) until late autumn. The reason for stopping in autumn is simply because the grass grows much slower in winter, so there isn't enough food to support lactating cows. However, it is entirely possible to milk longer than a year; I know of farmers who milk their cows continuously for two years. These farmers will have to purchase a lot of supplimental food (like hay or silage) during winter. The advantage of milking for longer than one season is that the cows do not have to give birth every spring, but instead only every second spring.
I believe (but can't guarantee) that in winter, most milk purchased in a shop comes from the opposite hemisphere. I do know that here in New Zealand, we export a lot of milk to northern-hemisphere countries.
If you were to suddenly stop milking a cow, they might get sick but generally they will survive. It's still something to avoid! Although if the calf is left with their mother then the cow would be relieved.
I do not have an 'official' source for these facts. However, I grew up on a dairy farm, so this was my life.
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$\begingroup$ Thank you very much. This answer seems most informative and real-life applicable. $\endgroup$ Mar 14, 2012 at 9:51
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2$\begingroup$ I was under the impression that certain breeds (holsteins for one) have been so over bred for the milk producing trait that there are periods where there milk production is so high, not being milked can actually cause the udder to tear allowing them to die from sepis. Note: that's anecdotal I don't have information confirming or denying it. $\endgroup$ Mar 28, 2012 at 21:50
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Dairy cows are bred, or selected to give milk. So they do produce excessively. The normal bovine wild type, like other mammals, not only produce less milk, but also will tend to stop lactating when the calf is not nursing.
I would be interested to know if dairy cows stop giving milk if they are not milked every day. I understand they can get very uncomfortable if they are not milked, but i don't know if they stop giving milk or if they are injured in some way.
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1$\begingroup$ Can you please provide a reference for the fact that if you milk a wild cow (good luck with that) every day, after removing its calf, it will stop producing milk at some point? Alo, if they are selected to produce more milk they do not produce it excessively. If you select a plant to have bigger fruits, its fruits are bigger, sure, but they do not grow excessively, they just grow the right size for that particular plant, which happens to be bigger than other plants. $\endgroup$– nicoMar 13, 2012 at 7:23
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2$\begingroup$ @nico "The calf is not nursing" I think he means after the calf is weaned. Also, 'excessive' is a relative term. A cow producing 4 1/2 gallons per day would be considered poor by the farmer, but is excessive in terms of her calf's needs. $\endgroup$ Mar 15, 2012 at 1:59
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$\begingroup$ @jmusser: that is what I am saying. If you get a wild cow and continue to milk it after weaning its calf it will most certainly continue to produce milk. $\endgroup$– nicoMar 15, 2012 at 6:30
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Cows only produce milk after a calf is born and their lactation period lasts approximately 10 months. In many instances, farmers have given growth hormone (GH)¹ to cows in order for them to produce more milk. It must be noted that there are many side effects associated with this, not to mention the residual effects it may have on us humans as consumers. Primarily though, the cows would have decreased immune efficiency and this would leave them vulnerable to all types of parasitic infections or disease.
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$\begingroup$ Welcome to Bio.SE. Can you give a reference to the GH use? The calf-bit is pretty much common sense So reference not needed there :) Thanks for your contribution! $\endgroup$– AliceD ♦Mar 11, 2015 at 4:10
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1$\begingroup$ Thank you for the welcome ^ ^ (is there a specific format for references) this is a scholarly article on the subject: goo.gl/MDvaDL ..also the wiki is found here: goo.gl/thQnmE $\endgroup$– aitíaMar 12, 2015 at 11:56
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$\begingroup$ If you click the link icon (the chain shaped icon) in the question window, it allows you to insert web links to articles etc. However - the wiki page you refer to is about sex hormones (estradiol, progesterone etc) and the article link is on antibiotics. I have downvoted your answer as it needs work since your claims about GH may be unsupported in the literature. After edits I am happy to upvote, don't worry. $\endgroup$– AliceD ♦Mar 12, 2015 at 12:00
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$\begingroup$ Thank you for explaining this AliceD, I have added a GH reference now. $\endgroup$– aitíaMar 15, 2015 at 19:13