Vets opinion on the spleen

[whorstman]

Originally Posted by paisjpq

predators hunt...prey gets eaten

K, , Who's hunting them? Havn't seen that on ESPN on weekend mornings. Is there a thouroughbred call?

[paisjpq]

Originally Posted by whorstman

K, , Who's hunting them? Havn't seen that on ESPN on weekend mornings. Is there a thouroughbred call?

you should watch the big game channel on the weekends...very informative.

[whorstman]

Originally Posted by paisjpq

you should watch the big game channel on the weekends...very informative.

Not sure I get that one on analog cable. Damn, guess I won't have the inside track to the Derby winner.

[docicu3]

C'mon now, next I'll be reading on here about strapping an oxygen mask on Curlin for a boost of good ole O2 right before loading the horse into the gate at 06:00 PM Saturday......only to be outdone by Dr Pletcher booking a hyperbaric oxygen room at 3 atmospheres for Any Given Sunday........

It may seem like a good idea to have a large spleen dumping venous blood already extracted of it's goodies from the arterial side hoping the extra RBC's might provide additional opportunity for oxygen delivery but if the hemoglobin value starts out normal then O2 delivery will remain unchanged.

or

DO2 = CO (cardiac output)/BSA (body surface area) X 1.34 (amount of oxygen dissolved in hemoglobin) X Hgb X SaO2 (oxygen saturation) X 10 (normal hemoglobin # in humans)

I am sure that horse normals are probably slightly different but the basic principles of oxygen delivery and extraction don't change.

So unfortunately we reach the limits of our physiology unless we can somehow dissolve more oxygen in hemoglobin to deliver to the tissues during anaerobic threshold. We can train animals to run efficiently just below AT but after that we run out of ways to manipulate the equation.

Unless you want to cheat........by milkshakes and designer drugs which help the animals to avoid AT......but nobody here would do that!!!!



For what it is worth splenic hypertrophy or hypersplenism in humans is associated with red cell imperfection such as in Thalasemia as the spleen hypertrophy's as it collects filtered denatured red cells. Broken shriveled red cells are as useless for carrying oxygen. So maybe Secreteriat had a massive spleen but thats not likely why he ran around race tracks like Kenyan's run up mountains.

Good luck this week DT's......

DrD

[paisjpq]

Originally Posted by docicu3

C'mon now, next I'll be reading on here about strapping an oxygen mask on Curlin for a boost of good ole O2 right before loading the horse into the gate at 06:00 PM Saturday......only to be outdone by Dr Pletcher booking a hyperbaric oxygen room at 3 atmospheres for Any Given Sunday........

never underestimate the things that go on training horses...there have been instances where horses are trained on a treadmill in a low oxygen environment in an attempt to give them an edge on raceday...and the hyperbaric chamber is used more often than you might think in an effort to reduce the potential for a horse to bleed.

and the spleen in a horse DOES operate differently than in humans...not all medicine can be definitively used cross species...almost half of all formed RBC's are stored in the horse's spleen, which as I understand it (I am not a doctor) differs from the human spleen which primarily stores platelets.

[Riot]

Originally Posted by docicu3

C'mon now, next I'll be reading on here about strapping an oxygen mask on Curlin for a boost of good ole O2 right before loading the horse into the gate at 06:00 PM Saturday......only to be outdone by Dr Pletcher booking a hyperbaric oxygen room at 3 atmospheres for Any Given Sunday........

It may seem like a good idea to have a large spleen dumping venous blood already extracted of it's goodies from the arterial side hoping the extra RBC's might provide additional opportunity for oxygen delivery but if the hemoglobin value starts out normal then O2 delivery will remain unchanged.
I am sure that horse normals are probably slightly different but the basic principles of oxygen delivery and extraction don't change.DrD

Horses do have some pretty fascinating and marked physiologic differences, Doc.

There are three ways to get better oxygen delivery to tissues: increased oxygen carrying capacity in the blood, increased cardiac output, and increased extraction of oxygen from blood at tissues.

Unlike humans, horses (and to a lesser extent dogs) store up to half their erythrocytes in the spleen, and markedly increase the unit volume of erythrocytes in the circulating blood via splenic contraction (their packed cell volumes - PCV - going from 40-50% at rest to 60-70% commonly), causing marked increases in overall hemoglobin availability while leaving plasma volume unchanged or slightly reduced (the increase in plasma viscosity is attenuated on the venous side by shifting of fluids extravascularly/intravascularly).

An exercising horse can increase its oxygen carrying capacity (hemoglobin) approx. 50% through splenic contraction and still not increase viscous resistance enough to impede cardiac output.

There is a linear relationship in the horse between PCV and speed until a max PCV of 60-70% is obtained. The spleen is larger in horses than in other species, and is larger in racing breeds of horses than in non-racing breeds.

The second variable is indeed cardiac output (CO = SV x HR). At rest the Thoroughbred horse commonly has heart rates in the mid-twenties to mid-thirties (I've monitored horses at rest that readily go into non-clinically significant 2nd-degree AV block), but during supramaximal exercise the TB horse commonly achieves heart rates that plateau around 210-225, but readily can achieve 240-250 bpm.

Additionally in the horse, it is documented that stroke volume does increase and contribute significantly to CO (increased myocardial contractility - Frank-Starling Law - reduced end-systolic ventricular volume, venous return supplemented by splenic contraction's contribution to blood volume, etc).

Horses can achieve a CO of more than 300 liters/min.

But the most important, that you touched upon, is oxygen consumption, influenced obviously by oxygen extraction.

Endurance-trained humans can increase their (tissue) oxygen consumption 18-24 x rest, but the athletic horse can achieve 40 x rest.

Max VO2 in human athletes peaks at about 100 ml/min/kg, while horses can exceed 180-200 ml/min/kg.

The arterio-venous oxygen content difference (a-v O2 difference) in elite human athletes can reach about 17 volumes percent, while TB horses can achieve in excess of 23 volumes percent.

Athletic horses and racing dogs (such as greyhounds) also have a high heart weight to body weight ratio (averaging 9.0 g/kg for the TB and 12.0 g/kg for the greyhound), while elite human atheletes achieve about 4.0 g/kg.

So yes - when searching for elite equine athletes, we do like to note spleen size (more RBC storage = more hemoglobin versus strapping on that O2 mask and increasing saturation), heart size, and some respiratory tract values.

[Danzig]

Originally Posted by whorstman

K, , Who's hunting them? Havn't seen that on ESPN on weekend mornings. Is there a thouroughbred call?

oh boy lol

way back when, before humans killed them all, predators used to hunt horses among other things....
basically, in nature, you're predator or prey. or sometimes (in our case) both--grizzlies certainly look at us at times as prey!!