Wikipedia:Reference desk/Archives/Science/2017 March 26

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March 26

Can food be made to be suitable for both dogs and humans?

I was checking this ad about Rachael Ray's Nutrish Dog Food. It had chicken, rice, fruits and vegetables. This made me think what would happen if a human just prepares a meal with chicken, rice, fruits, and vegetables, cooks it, and then feeds the meal to the dog. Assuming that the dog is treated like a human family member with specific food needs (such as no garlic or salt or sugar), can food be prepared in a way that would be suitable for both human and dog? How much overlap is there between the nutritional requirements of human and dog? 50.4.236.254 (talk) 01:59, 26 March 2017 (UTC)

Quite a bit of overlap. But the question is if there is anything vital to one which is deadly to the other. Assuming not, there's still the issue that a dog diet is mostly meat, and that's not the best diet for people. If that's the only issue, you could have dog food plus something extra for the people (more fruits, veggies, onions, beans, nuts, mushrooms, etc). Also note that some foods that might not harm your dog might cause undesirable effects, like beans and onions. StuRat (talk) 02:03, 26 March 2017 (UTC)

The Nivkh people, of Northern Sakhalin and the Amur river traditionally hunted fish which they buried in pits and pickled. They then fed the season's batch to dogs, which canines they then ate. On eating dog. μηδείς (talk) 02:33, 26 March 2017 (UTC)

... and the assertion that Nivkh people eat dog-meat seems totally inconsistent with everything I've ever learned about Northern indigenous cultures. In fact, the source you linked states: "Nanai hunters treated their dogs with respect and love; the intelligence and courage of the Amur Laika during hunting was particularly welcomed." Would you care to rescind your statements, or did you actually have a real source for the outlandish claim that the dogs were used as meat-animals? Nimur (talk) 03:37, 30 March 2017 (UTC)

The linked document states "Nivkhs and Ainu also used dogs for both sledding and hunting, but they also ate dog meat and they ate it not only during rituals, but also as a regular table meal". Iapetus (talk) 12:55, 30 March 2017 (UTC)

I am old enough to remember when it was quite common to feed one's pet dog with leftovers from meals. The concept of packaged pet food in its infinite varieties is relatively new. One didn't see too many obese dogs then. Richard Avery (talk) 07:26, 26 March 2017 (UTC)

Note that Cats definitely need Taurine, which is not found in many human foods other than Energy drinks. And I certainly do not recommend giving energy drinks to a pet! (I don't think pets handle Caffeine well). Do dogs need Taurine too?

Also, note that chocolate and onions can both be toxic to dogs. Chocolate is toxic to cats too, but I believe that most cats, unlike dogs, tend to turn their whiskers up when offered chocolate, whilst dogs are more likely to actually eat it. I stand to be corrected.

Also, junk food is bad for dogs too, ok? So skip those sausages and burgers, they tend to be packed with salt and saturated fat. I don't think they're good either for you, or you dog? Eliyohub (talk) 19:40, 26 March 2017 (UTC)

it's not a case of onions and chocolate can be toxic to dogs, they are both extremely toxic to dogs, as is garlic. Onions and garlic both contain thiosulphate which causes hemolytic anemia, characterized by damage to the red blood cells.[1] Richerman (talk) 22:36, 26 March 2017 (UTC)

Richerman is correct but it is important to realise it is the type of chocolate which determines whether it is toxic. Several companies have developed chocolate treats for dogs which are not toxic - try a Google search with "chocolate for dogs". DrChrissy ^(talk) 22:48, 26 March 2017 (UTC)

Theobromide would be the culprit compound. It's interesting that dogs would like chocolate. Am I correct that most cats don't care for it? I think cats are believed not to be able to taste sweetness? It's not really part of their diet. Am I correct? And are dogs different in this regard?

Also, is Taurine vital for canine nutrition, the way it is for felines? Eliyohub (talk) 23:03, 26 March 2017 (UTC)

No, it is not essential in a dog's diet, but it IS essential in a cat's diet. Dogs can synthesise taurine in their own body, but cats can not.[2] However, in some conditions, a dog may require Taurine supplements. DrChrissy ^(talk) 23:10, 26 March 2017 (UTC)

Cats and sweetness Cats lack the gene for detecting sweetness, so it is rather unlikely they will be attracted to it.[3]. The articles states cats are the only mammals lacking the gene - which I find rather surprising. DrChrissy ^(talk) 23:18, 26 March 2017 (UTC)

Cats are obligate carnivores, eating plants only medicinally, while most other carnivorans are predominantly but not exclusively carnivorous. Given this, cats have no need to taste sugar, so their having lost the ability may have happened randomly, but failed to be a disability, so the sweetblindness simply spread since there was no advantage to maintaining the ability. The same phenomenon seems operative in primates. Since primates eat fruits and greens, they have lost the ability to synthesize vitamin C, since their diet is full of it. Humans are the only primates who have moved out of areas and into niches where they have to seek out vitamin C.

Cats and dogs have smaller livers (by body weight) than humans, with less of an ability to deal with alkaloid plant poisons. We would die too from coffee or chocolate if we consumed it in similar quantities by weight and could not metabolize it with our very large livers. μηδείς (talk) 00:02, 27 March 2017 (UTC)

I'm trying to reconcile two apparently contradictory pieces of information: (1) Cats regularly get killed by licking up ethylene glycol-containing antifreeze, which they do because it's sweet; (2) cats can't taste sweetness.

Can anyone explain this? --Trovatore (talk) 17:21, 27 March 2017 (UTC)

This site claims that antifreeze though toxic and potentially lethal has a smell and taste that cats are attracted to. Although I provide a dish of fresh water for my cat he is far more interested in sipping from random sources such as puddles or a dripping tap, which I assume reflects his territorial concern with urine marking. Blooteuth (talk) 19:25, 27 March 2017 (UTC)

I fairly doubt anyone has actually developed chocolate for dogs. As our article says chocolate implies you have cocoa at least cocoa butter for white chocolate. While admittedly cocoa butter doesn't have much theobromine, it's still not generally recommend for dogs.

And in any case, if someone refers to a chocolate treat for dogs, they aren't generally referring to white chocolate but some form of brown chocolate i.e. which should have cocoa solids. And while it's true that if you use minimal solids you won't have that much theobromine so the actually level the dog has to eat may be high enough it's really unlikely to be a problems, you'd really want to breed it out of the cocoa if you really want to give non white-chocolate (i.e. something containing cocoa solids) to dogs.

Much more commonly people sell treats that are like chocolate but aren't. E.g. carob is a common one for dog treats. Other ones like this [4] [5] don't really say what they use and I doubt meant people have eaten them so who knows if they even really taste like chocolate.

This isn't simply a matter of semantics. While it's true that some chocolate milks and ice creams etc barely have any cocoa solids, generally speaking chocolate implies cocoa and since it's best to avoid giving anything with cocoa to dogs (and cats), it's far better to stick with treats which are actually clear what they are rather than claiming they are chocolate when in fact it's better if they aren't chocolate.

This also avoids the confusion of people thinking some chocolate is okay for dogs when it's best to think no chocolate is okay for dogs and treats for dogs which are okay simply aren't chocolate. (Whether using carob or some artificial flavours known to be safe dogs.)

Nil Einne (talk) 08:43, 27 March 2017 (UTC)

Here's what some of them contain - they should really be called chocolate substitute but they tend to use the term choc drops, which is somewhat misleading.[6][7] Richerman (talk) 14:32, 27 March 2017 (UTC)

I think people may have a slightly exaggerated notion of how toxic chocolate is to dogs. My brother-in-law's small dog once found a hundred bucks worth of See's and had at it. If I understand correctly, he did leave his stomach contents lying around in inconvenient places, but was fine after that.

So obviously I'm not saying feed your dog chocolate, but it's not exactly cyanide. --Trovatore (talk) 17:40, 27 March 2017 (UTC)

For God's sake this is supposed to be the science reference desk. It depends on the amount of theobromine consumed per Kg. It is toxic in quite small amounts, >20mg/kg is toxic, 100mg/kg is probably lethal, see [8] and obviously there would be many factors to take into consideration. What was the concentration of theobromine in the chocolate? How much of it stayed in the dog's system and was absorbed rather than being vomited up? What was the long term effect on the dog's health? Richerman (talk) 22:42, 27 March 2017 (UTC)

Of course I don't know any of those things. Just the same there is a bit of a panic atmosphere about chocolate that is not really justified. Theobromine has harm potential because it's a stimulant. It has a longer half-life in dogs than in humans, which as I understand it is the main reason it's more dangerous to dogs. Don't go feeding it to your dog on purpose, but if he licks your bowl after you've finished your chocolate ice cream, call the vet if you like; he/she knows better than I do. But my prediction is you'll be told not to worry. --Trovatore (talk) 22:56, 27 March 2017 (UTC)

User:Eliyohub, you obviously glanced at taurine, but stating that it's "not found in many human foods except energy drinks" is completely wrong. It is found in most meat products, including chicken, fish, mammals, etc. Matt Deres (talk) 00:44, 27 March 2017 (UTC)

When I worked in a market, one lunchtime a boy on the next stall (who had a reputation as a joker) offered me a tin of luncheon meat. I opened it up and began eating. After a few seconds I spotted the words "dog food" on the label and that was the end of the meal. 86.169.56.176 (talk) 17:14, 27 March 2017 (UTC)

Did it taste bad? I mean, worse than canned meat ordinarily tastes? I'm thinking, if it won't hurt the dog, it probably won't hurt you either. --Trovatore (talk) 17:25, 27 March 2017 (UTC)

Getting back to the OP's question, yes, you can feed chicken to dogs (and cats), however, it is highly recommended that you do not give them cooked bones.[9] Cooked bones have a tendency to splinter and may perforate the gut. DrChrissy ^(talk) 21:18, 27 March 2017 (UTC)

Of interest to OP may be Yaff bars. They are an energy bar that is safe for both humans and dogs. They're made by Mudd and Wyeth. I'd link to their web site but it doesn't seem to load correctly for me. They're predominantly made as a snack during hikes and such. Not as a major nutritional staple.

And yes, you should not feed cooked poultry bones to dogs. I feed my dogs a raw diet and they get raw bones. No cooked ones. See Raw feeding for more on that. †dismas†|^(talk) 21:32, 27 March 2017 (UTC)

The website I provided above recommends NOT to feed ANY cooked bones to dogs, not just poultry. DrChrissy ^(talk) 22:47, 27 March 2017 (UTC)

This is a bit outside my skill-set. Producing stock and bouillon is easy if one has a lot of chicken bones. (ie after big reception party). A modern blender will usually brake up almost everything. Marinate in vinegar for a couple of days and the calcium structure of the bone will start to weaken and dissolve. Place in pressure cooker and wait for an hour. Strain out (what little solids remain -if any) through muslin bag. An hour in a pressure cooker usually produces just pure liquor. Place portions in freezer bag an freeze until required. Never thought nor considered whether this may be suitable for dogs though, so take this with a pinch of salt. Another thing, When raising pullets (young hen chickens) it is important to ensure that they get enough calcium to produce eggs with strong shells. So bone-meal is often used as a dietary supplement. That bone-meal doesn’t puncture the gut because is is finely ground, more so than a snail shells which they will also gobble up. Off topic: don't feed chickens, dogs, cats, humans with bones of their own kind. Don't know what the scientific evidence is but folk-law warns against it. Like Kuru (disease) and mad cow disease. Personally, think it is a lot of effort to go through, but perhaps, if one keeps bunging the bones in the freezer until there is enough to fill a pressure cooker, it might be just worth while. But as said above, feeding cooked bones to dogs without some further post-possessing seems like a bad idea. It could ruin your dog's whole day. They don't normally eat fowl nor cooked bones as part of their normal diet. When I was at school, dogs preferred eating my homework – 'anyway, that was my excuse ;¬ ) --Aspro (talk) 15:44, 28 March 2017 (UTC)

Cannibal cows (for BSE) are the standard reference. Wnt (talk) 22:48, 28 March 2017 (UTC)

In addition to the above. In the aftermath of the BSE epidemic, it was suggest, put forward, and backed up by reasonable evidence, that the sudden wide spread of the disease was due to to the use of a bovine inoculation, injected into cattle and derived from a cow with prion disease . This was politically sensitive. The manufactures had been granted legal immunity by the government. The full truth of matter has still not come out. Yet, the areas where BSE became epidemic are in the areas in which that these inoculations were being used routinely. Many a dairy farmer went out of business because the compensation did not cover his total costs of loosing his herd. This wasn't just the odd cow but lots.--Aspro (talk) 18:44, 29 March 2017 (UTC)

Why don't they make non-hybrids with 2 or 4 internal combustion engines?

Each driving half or 25% of the wheels and a computer doing everything the mechanical linkages like differentials used to do. Smaller engines have higher power to weight ratios. Sagittarian Milky Way (talk) 02:56, 26 March 2017 (UTC)

Are you sure that smaller internal combustion engines are more efficient, including all the connection lines and hoses for spark plugs, fuel lines, air supply, cooling, controls, etc ? I don't think of small gasoline engines, like lawn mower engines, as being very efficient. Small electrical engines, on the other hand, do seem efficient, so having one drive each wheel does seem like a viable option. StuRat (talk) 03:03, 26 March 2017 (UTC)

I speculate that IC engines are not responsive enough to support sufficiently precise control of torque and RPM to eliminate the differential. In addition, an IC engine is efficient over only a small range of RPM, so the engines will all require gearboxes, and this negates most of the potential gains. By contrast, electric motors are quite responsive and do not need to shift gears to maintain efficiency. -Arch dude (talk) 03:33, 26 March 2017 (UTC)

The "Sahara" model of the Citroën 2CV had two engines to create a 4-wheel-drive system for desert travel. -Arch dude (talk) 03:33, 26 March 2017 (UTC)

It would waste energy. Only a fraction of the energy consumed by an automobile's internal combustion engine actually goes to the wheels. See: File:Energy flows in car.svg, [10], [11]. If you have two engines, now you're wasting twice the energy. Actually it's even worse than that, because you have the added weight of the extra engines, plus you would need to design the cooling systems, drivetrain, etc. to accommodate the multiple engines, which adds even more weight (not to mention more stuff that can break). Electric motors are a lot lighter, more efficient, and generally provide much better torque than an ICE; that's why multiple electric motors can make sense. Compare this breakdown of electric vehicle losses to what I linked before. --47.138.161.183 (talk) 03:49, 26 March 2017 (UTC)

It's not quite that bad, because each engine is smaller and/or runs slower. StuRat (talk) 03:51, 26 March 2017 (UTC)

If they do this anywhere, certainly it will be with those mining trucks that have tires the size of houses. I'm no expert, but I'd look there, for the same reason that large dinosaurs often had secondary ganglia to handle impulses too far from the brain. μηδείς (talk) 04:06, 26 March 2017 (UTC)

Such large vehicles usually use diesel-electric transmission. Yes, it actually saves energy to have an ICE turn an electric generator and then use electric motors to turn the wheels, because you can dispense with the extremely large and heavy transmission that would otherwise be required, and the ICE can then always turn at its most efficient RPM range. --47.138.161.183 (talk) 04:16, 26 March 2017 (UTC)

This reminds me of Diesel-electric locomotive and variants. PaleoNeonate (talk) 05:16, 26 March 2017 (UTC)

Yes, diesel-electric locomotives use a diesel-electric transmission as well (the lead image on the latter article is a locomotive). Some large ships also use it: integrated electric propulsion. (On a side note I think the big batch of marine propulsion articles could use some cleanup and merging.) --47.138.161.183 (talk) 09:26, 26 March 2017 (UTC)

As OP didn't say this is about road vehicles, what about diesel-hydraulic multiple units? Every car (or maybe 2 out of 4 cars) has its own diesel engine to power the axles of that car, as it's not feasible to have mechanical power transmission from one car to another. Diesel-electric multiple units may use a single engine with electrical transmission to other cars, or multiple engines for reliability or space considerations: multiple small engines can be put under the floor, a single big one needs an engine compartment. Although a single big engine is somewhat more efficient. PiusImpavidus (talk) 09:57, 26 March 2017 (UTC)

• This is difficult to arrange, but has been done. Mostly it's an issue for petrol engines. Petrol engines are throttled to control their power, so they are inefficient at part-throttle. The situation is much better for diesel engines, which are controlled by their fuel supply.

A few vehicles, mostly larger ones, have used multiple prime movers, switchable individually. Larger ones have more fuel to save, more scope for the "overhead" of the switching and may need multiple power units anyway, just on the size basis. On railways the British Rail Class 55 Deltic (diesel-electric) could do this, as could the diesel-hydraulic Class 52 Westerns, both with two engines. The Deltic could drive all of its traction motors in such a case, the Western only drove a single bogie. On ships, an electric transmission is often used to arrange this control from multiple engine-generator units.

For cars, the Cadillac L62 engine first used a system of switching pairs of cylinders for its V8 engine in and out of use. Andy Dingley (talk) 10:36, 26 March 2017 (UTC)

• The claim that "petrol engines... are inefficient at part-throttle" seems very odd in view of the standard advice that using the highest possible gear for the circumstances—thus, throttling the engine down as much as possible—produces the greatest fuel economy when driving a car. --76.71.6.254 (talk) 11:53, 26 March 2017 (UTC)

The advice applies to cruising at constant speed where less than maximum engine power is required. "The engine in a car cruising on a highway is usually operating significantly below its ideal load, because it is designed for the higher loads required for rapid acceleration." Using highest possible gear implies the engine delivering near its maximum power at a low r.p.m. i.e. near full throttle.[12]. Blooteuth (talk) 14:47, 26 March 2017 (UTC)

(1) The linked article does say that, but it also says "citation needed". (2) If it's at a low rpm, it's not near full throttle. Full throttle refers to the condition when it's throttled as little as possible, developing maximum power. (3) By the way, please link to Wikipedia articles using wikilinks rather than external links. --76.71.6.254 (talk) 05:02, 27 March 2017 (UTC)

using the highest possible gear for the circumstances—thus, throttling the engine down as much as possible: incorrect, that is the other way around. At constant vehicle speed, a higher gear will use a lower engine speed and higher engine load, hence less throttling (generally speaking). Engine noise which "tells" you to switch to an upper gear is related to engine rotation, not torque. Tigraan^{Click here to contact me} 15:03, 26 March 2017 (UTC)

This may be a vocabulary confusion. "Full throttle" refers to the throttle setting and corresponds to maximum power. "Throttling" refers to the throttle's action, which is to reduce power by restricting the supply of fuel and air, so there is less (not more) throttling at full throttle. --76.71.6.254 (talk) 05:02, 27 March 2017 (UTC)

I confirm that by "near full throttle" I meant near maximum power i.e foot down, "pedal to the metal" (which is quite different from "throttled down"). That understanding should have been obvious from the context, except apparently to IP user 76.71.6.254. That IP user might usefully register and thereafter try to supply referenced answers instead of treating this desk as a forum for belittling other posts. Blooteuth (talk) 18:56, 27 March 2017 (UTC)

It was not my intent to belittle anyone, but somebody is confused on an issue of fact, which is appropriate to discuss here. I honestly thought that a misunderstanding of how the directions of the throttle control are described might explain it. The thing that I thought "should have been obvious" was that if you use a lower gear (for the same speed of travel), you have to step harder on the accelerator to keep the engine running at the higher rpm, otherwise engine braking will occur. And therefore that using a higher gear (for the same speed of travel) corresponds to throttling down more. And I did supply a reference for my original point, and I have no interest in registering. --76.71.6.254 (talk) 23:11, 28 March 2017 (UTC)

• Continuous variable transmission may be of interest: engine efficiency is maximized at the expense of drivetrain losses (and production cost). Tigraan^{Click here to contact me} 15:06, 26 March 2017 (UTC)

That (and the point above) are a separate approach to a separate problem, that of matching rotation speeds. There is still an underlying problem, which is that some engine types (petrol rather than diesel, but especially gas turbines) have efficiency at part load that's much worse than their best efficiency at optimum load. Andy Dingley (talk) 17:35, 26 March 2017 (UTC)

Biology shows that the most efficient engines are of molecular size, you can then extract a large fraction of the maximum possible work which is the difference in the Gibbs energy of the fuel and its combustion products. If larger engines were more efficient then after hundreds of millions years of evolution, animals with large combustion chambers would have evolved. Count Iblis (talk) 19:29, 27 March 2017 (UTC)

The last point is a non-sequitur. Not all "perfect" solutions can evolve, since there are physical impossibilities or the intermediate steps don't work. Otherwise we'd have animals with wheels instead of hooves, of course. μηδείς (talk) 20:49, 27 March 2017 (UTC)

Funny you should say that ; -)

Animal with wheels and no hooves.

--Aspro (talk) 23:02, 27 March 2017 (UTC)

Lithium-ion batteries exploding from a short-circuit

I asked an earlier question about the hazards of Lithium and Lithium-ion batteries. They're far more dangerous than I had ever thought. Particularly given the difficulty of extinguishing them, given that oxygen starvation does not work very well, if at all.

My question is, how much power would a lithium-ion battery need to be holding, to explode or catch fire purely from being short circuited? I'm talking about a continuous short-circuit, not a momentary one. Is this something measurable? Have any studies or estimates been done? What would be the calculations? I aint doing any actual lab tests of this myself, thank you! (I don't want to need to be calling a HAZMAT team!) Is there any "formula" for calculating this? Is there a specific temperature at which a lithium-ion battery self-ignites? And can the rate of heating from a short-circuit be calculated, if you know the battery size and power, and how much charge it holds? Would heat loss (insulation, ventilation, or lack thereof) also come into the picture? As this is a known hazard of modern batteries, I assume studies and calculations would have been done on this? Eliyohub (talk) 19:26, 26 March 2017 (UTC)

This is a great question, but I'm not sure how much can be answered in the general case: each battery vendor, each mechanical packaging process, each chemistry, has different parameters for thermal coefficients, energy density, peak theoretical discharge rate, and so on. It's a lot easier to answer a related question: what standard model(s) and equation(s) do battery engineers use in their design? Then we could apply those standard models to a specific case. Unfortunately, "I don't know"... but I can look around and see if I can find a good resource to get the interested readers started in the right direction.

I did find this product safety data sheet from major battery-retailer Energizer. It refers you to contact your sales-representative for further technical documentation - which isn't a straightforward path for the casual non-industrial researcher! The batteries in your standard modern electronic toy aren't even likely made by them or their affiliates - your average toy contains a batter that's probably made by some unnamed third-party vendor by way of some further-anonymized wholesaling vendor via some contract manufacturer - it's quite difficult for an end-product consumer of a retail electronic device to follow the supply chain upstream and get real technical information on the parts they have in hand!

We also need to distinguish between simple cells and complete electronic products. Simple cells are extraordinarily dangerous - they are basic bags of raw chemical. Batteries that you find in most finished-product retail-quality batteries - even in all their various standard and non-standard shapes - usually also contain a built-in battery management system and protection circuitry. You can short the package terminals together, but the safety-circuit prevents you from short-circuiting the actual battery cells. This is called overcurrent protection and a zillion standard methods exist to implement it. We can find whole books analyzing the design and practice of such circuitry - and with enough analysis, we could also consider failure-modes of the protection circuit, including circumvention of the protection by inducing external mechanical, electrical, and thermal damage.

Nimur (talk) 20:58, 26 March 2017 (UTC)

These sources look like they could be of interest [13] [14] [15] [16] [17] [18] [19] [20]. You'll probably find more by following the various links (I actually found the 3 after the 1st from what were 'recommended'. I didn't read them that well but a quick look at the first suggests they found a full charged (to 4.2V or higher) LIP with 260 mAh or higher capacity was at risk of thermal runaway. You'd note that several of these deal with internal shorts. This is probably because, as the last refs somewhat emphasise and mentioned by Nimur, most finished products have protection against external shorts. Even many simple loose 18650 cells that people sometimes use for torches etc often come with simple protection (generally for short circuits, over discharge and over charging), although this isn't to suggest there aren't also a lot of unprotected ones too (they are used by people reconstructing battery packs for example). Nil Einne (talk) 00:52, 27 March 2017 (UTC)

I question the OP's terminology, i.e., "How much power.." A more reasonable question in this case is "How much energy..." Power is not the same as energy. Edison (talk) 02:37, 28 March 2017 (UTC)