ATI Wisdom Booklet 6: Science - Sheep!

My husband is a dairy farmer.  He operates and acts as one of the herdsmen for our 1,200 milking head herd with a similar combined number of young stock and steers.  He also earned a technical degree in dairy management before completing his Bachelor's Degree in Animal Science from our local land-grant college.

Why do I bring this up?  He's got a strong background in ruminant physiology,  behavior, and feeding patterns.   This section made his blood pressure go through the roof because it's THAT inaccurate.

• Digestion is all of the mechanical and chemical processes required for an organism to change food from the form consumed to the form that can be absorbed by the body.  Chewing food originally and chewing cud are both part of digestion.
• Ruminants LIKE to rest while chewing cud, but it is not required.  "Undisturbed quiet" is a matter of perspective.  Herd animals tend to do things in tandem, but for safety reasons, there are always a few individuals who are out of sync with the group.  For example, in a group of 200 sheep, 190 of them may be lying down while chewing cud and in a zoned out state.  The other 10 will be nursing calves, eating grass or getting water.  These individuals are also behaving as sentinels who are the most likely to see predators approaching.  The reverse also happens where most of the herd is up and active while a sheep or two is chewing cud and blissfully zoned out.

Pretest time!

• Prayer or helping others?  Seriously, where are the science questions?
• Sheep can graze closer to the ground than cows.  They need less food per animal because of reduced body size.
• Well, a cud chewing ruminant is about as close to the state of Zen as I have ever seen...
• Um...the mental state of a cud-chewing ruminant?

• *Snickers*  Think about that statement for a minute.  If sheep cannot find food without a shepherd, that means that a herd of sheep in the middle of a pasture without a human will starve to death.  Does that sound reasonable?    I didn't think so.  This is especially ironic since sheep are one of the least picky grazers on a farm.
• The larger problems are protecting sheep from predators, protecting sheep from themselves, and keeping the sheep from overgrazing the pasture.  That's why sheep need shepherds.

• Sheep aren't really defenseless.  
• They can kick and bite. They can also butt The problem is that they aren't strong enough to fight off predators like bears, wolves or lions.  
• Hiding isn't a good option for grazers.  Grass grows best in full sunlight.  Hiding is most effective in brushy or dark areas, so the herd would have to be running back and forth all day.  Instead, sheep hang out in herds where many eyes are watching for predators and if a predator attacks, the probability of a single sheep being attacked is diluted by the total number of sheep in the herd.  In other words, if a lion sees a single sheep, the probability of attack for that sheep is 100%.  If a lion sees a sheep in a herd of 100, the probability of attack for that same sheep is 1%.
• The factoid about the normal body temperature of sheep is interesting, but pointless.  Sheep overheat because they are wrapped in wool which traps heat and limits the effectiveness of sweating.  The same line of logic used in the paragraph above would indicate that frogs are much better distance runners than humans because frogs have lower body temperatures.....

• This is true for all grazing livestock.  Cows will happily chow down on plants that will make them severely ill or die.  Horses can eat themselves sick on hay.  

• Kind of true.  Livestock get thirsty and will drink water when they need it from the nearest water source.  
• The real trick is getting the livestock the parasite-free water that they need without polluting the water with animal manure.  All the livestock operations around here that I know of use waterers which are pumps attached to a well that dispense water into a tank the animals can drink from.  This allows the farmer/rancher/shepherd to fence off the local ponds, lakes and streams to keep the livestock out.

• Um...kind of.  Cows and sheep graze differently.  
• On a good pasture with breeds of cattle that are good grazers, cows will take a mouthful of grass and use their neck muscles to rip the leaves off the plant.  This means that they can't get a hold of plants that are shorter than 2 inches from the ground. 
• Cows can be extremely picky eaters.  When we put a group of young cattle on a fresh pasture, they will methodically eat all of the clover and lambs' quarter that they can find in the first 24 hours.  After the "tasty" foods are gone, they start eating grass.  
• Holsteins - our standard black and white dairy cows - are horrifically bad pasture animals in part because they are such picky eaters.  I once watched one of our young heifers systematically eat the flowers from a thistle plant.  This required her to maneuver her lips and tongue to pull the petals off while avoiding the prickers.   After an hour, she had removed all the flowers which may have given a total of 50 calories instead of a few thousand calories of grass.  Oh, and she looked around the pasture to see if there were any more thistles plants to eat.....*sighs*
• Sheep can graze much closer to the root of the plant because their muzzles are much smaller.  They are also much less picky than cows or horses are about the plants they eat.
• I hate the term "nip" here.  That implies that the sheep can cut the grass with their teeth.  They can't.  Cows, sheep and goats lack upper incisors.  They have a dental plate on top - a flexible, studded tissue that the teeth hold the grass against.  The actual grazing motion for all three is a tearing of the grasses.  
• They can, however, still bite people.  Getting a part of your body between the molars of a cow still hurts.  And the bottom incisors are amazingly sharp in newborn calves, as I found out when I've tried to stick a finger in a calf's mouth when feeding them.

• Oh, damn.  
• Look, a healthy ruminant's digestive system NEVER shuts down.  EVER.  If the digestive system stops, the fermentation that is always occurring in the rumen and reticulum will produce gasses that cannot be expelled.  This is called bloat and it will kill the sheep if it is not treated promptly.
• I don't know what ATI means by "digestive juices".  In humans, it's a combination of enzymes released by the body and bacteria that break down chemicals.    Sheep release some chemicals into the rumen and maintain a healthy ecosystem of bacteria.

• The problem with this statement is the word "begin".  The verb "to begin" implies that sheep stop grazing at some point.  They don't stop.  That's the tradeoff of being an obligate herbivore; plants are everywhere, but not very energy dense so sheep (and other ruminants) are generally spend 8-10 hours a day grazing and 12-14 hours chewing cud.  The remainder of the time is used mostly for traveling to water, socializing, and various forms of self-care.  Cows sleep for a whopping 20 minutes a day although they do spend much of the cud-chewing time in a drowsy, dozing state.

These ATI posts are getting too long for my tastes, so I'm going to divide them in half to make management easier for me.