Wednesday, July 4, 2012

On-Farm Hydration Strategies

How many cows are lost to dehydration?  Imagine eyes deep in her sockets, skin refusing to snap back in place, udder rung tighter than a dish-rag, heart racing, and weakness.  Without immediate, aggressive hydration therapy, she may die.  This scenario is seen over a variety of health problems, from toxic coliform mastitis and metritis to profuse diarrhea from dysentery and as corrective treatment before, during, and after surgery.  When we are presented with these patients, many times we shake our head, run our fingers through what little hair we have left, try to bite our tongues from saying something sarcastic because prevention of the initial insult saves and makes more money, but in the end, we have a teaching moment.  Strategies exist to rehydrate the cow on-farm. 

A milking cow has a water consumption requirement between 20-40 gallons per day with higher needs under heat stress conditions.  A 1500-pound non-lactating dairy cow requires at least 9 gallons of fluids daily for maintenance.  Lactation and heat stress increase fluid demand, an additional 11 to 31 gallons above maintenance.  Now let’s add a severe insult to the system.  Diarrhea has the potential to cause over 27 gallons in fluid losses daily in a 1500 pound cow.  So what can we do on farm to correct the fluid losses?    

First, we must learn to assess the degree of dehydration using the cow’s eyes, skin tent, mucous membranes.  By classifying the degree of dehydration, we can tailor a hydration protocol for the individual cow. 

  • 6-8% Dehydrated:  Slightly sunken eyes, Slightly increased skin tent (2-3sec),  Moist mucous membranes
  • 8-10% Dehydrated:  Obvious sunken eyes, Obvious increased skin tent (3-6sec), Tacky mucous membranes
  • 10-12% Dehydrated:  Profound sunken eyes, Skin Tent >3 seconds duration, Dry mucous membranes, Rapid Heart rate, Cold Extremeties, Very dark urine, Depression

Hydrating the cow orally, through a pump system, is the easiest means of rehydrating the cow on-farm, giving the cow the most vital nutrient - water.  The rumen in an adult cow can easily accommodate 10 gallons of fluid.  To place the 10 gallons of drench into your cow, you can never go wrong using the Magrath Cattle Pump System.  Studies have shown that most off-feed cows are alkalotic, not acidotic, so it is critical that you select an oral solution that is non-alkalizing.  If they are alkalotic, why do so many off-feed cows get those alkalizing pink pills?  Hmmmm, something to talk about with your vet!  A simple non-alkalinizing oral solution would include 140g NaCl, 25g KCl, and 10g CaCl2 in 5 gallons of water.  Pre-formulated and packaged drench mixes can also be utilized such as Advanced Agri-Solutions Oral Drench Mix which contains ingredients that address subclinical hypocalcemia, stimulate rumen microbial growth, and provide energy precursors for the ketotic cow.  

For cows between 6-7% dehydrated, oral rehydration will meet the cow’s fluid deficit.  Cows that are 6% dehydrated need 11 gallons and individuals 7% dehydrated require 12 gallons for fluid replacement.  Remember to thoroughly mix the solution/drench mix in warm water, the same temperature as the cow, 101.5F.  Make sure the hose is in the esophagus before pumping.  Just like tube feeding a calf, you will not be able to easily palpate the hose in the hard, cartilaginous trachea.  Do not allow the cow to raise her head in order to prevent her from inhaling regurgitated drench mix or saliva.  Take your time and pump slowly to prevent regurgitation, especially with jerseys.  Avoid pumping the bloated cow or a cow with a grossly distended abdomen and instead rely on IV rehydration strategies.

Cow’s that are greater than or equal to 8% dehydrated need IV therapy in addition to oral rehydration.   To correct fluid deficit, a cow 8% dehydrated requires 14 gallons of fluids.  So, if we can squeeze 12 gallons into the rumen, a deficit of 2 gallons still remains.  At ~4 Liters per gallon, the cow requires 8 L administered intravenously!  Your head starts turning when you consider higher dehydration levels.  In addition to 12 gallons in the rumen, dehydration statuses of 9%, 10%, 11%, and 12% require 16L, 24L, 32L, and 40L of IV fluids!  

Let’s start with Hypertonic Saline 7.2%.  Hypertonic saline rapidly expands the vascular fluid volume by pulling fluid from the non-vascular space, like the large rumen water reservoir and tissues, into the blood vessels or vascular space.  Hypertonic saline is easier to administer than larger volumes of IV fluids.  After heating to 101.5°F, administer 2L through a 14g needle in the jugular vein over 8-10 minutes.  Repeat once in 24 hours.  After the IV, cows typically drink 8-10L of water.  Remember cows prefer warm water.  However, if no water is consumed, pump the cow immediately. 

Cows within the 10-12% dehydration range will require more than just hypertonic saline and pumping to correct their fluid deficit.  Large volume IV fluid therapy is necessary. Remember most cows are alkalotic, so a non-alkalizing IV solution is required such as Normal Saline or Ringer’s Solution and avoid alkalizing solutions like sodium bicarbonate solution and lactated ringers.  Normal saline and ringer’s solution can also be administered safely under the skin over multiple sites.  Just remember, to warm all fluids, no matter the route of administration (IV, under skin, or orally) to the cow’s body temperature.  Do not exceed 10-12L/hour intravenously.  The probability for survival greatly improves with rapid administration of large volumes (10-20L) of IV fluids.  Surgical outcomes also improve with IV fluid therapy before, during, and after surgery, helping to restore blood flow to compromised tissue.  How much patience do you have?

To save a cow, you can discover some patience.  Repeat fluid therapy to correct ongoing fluid loss and to cover maintenance requirements (9 gallons) and milk production (22 pounds of milk equals 2.6 gallons water for example) if the cow fails to drink sufficient fluids.  Many off feed cows and particularly toxic cows require calcium, 250-500 ml 23% calcium gluconate. 

If you can pump a cow and place a needle into the jugular vein you can correct hydration, save cows, and hasten recovery from disease.  Never fail to consult your veterinarian to tailor rehydration strategies to your farm. 

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