6/24/07

Welcome to the Game Ranch Health newsletter.  This section is used to address important facets of health management for game farms and ranches in this column in a timely, frequent fashion.  Please keep visiting our website frequently to check our newsletter section for future articles.  Our promise is that they will be concise, pertinent and factual.  If they are enlightening, thought provoking or entertaining, that will be icing on the cake.

#1  Intestinal Parasite Control

Several years ago I co-authored a survey of the exotic hoofstock industry in Texas (Exotic Ungulate Production: Summary of Survey, Texas Agricultural Extension Service).  It covered a myriad of subjects but my focus was on the medical issues of game ranches.  One of the telling health statistics reported was the fact that 58% of animal health problems on Texas game ranches were related to parasitism.  In light of this it was no surprise that 75% of the surveyed game establishments employed some form of parasite detection/treatment.

Gastro-intestinal parasites pose even greater problems today in the deer and antelope industry.  This is because several species of these nematodes (intestinal worms) have become resistant to the common veterinary drugs that have been used to treat them for many years.  While the worms have become resistant, medical science has lagged behind in its attempts to find new anthelmintcs (de-wormers).  These future products should be from totally different drug families than products that are presently used. 

The growth in intensive white-tail deer farming adds to the parasite paradox.  Because they are browsing animals by nature they have less resistance to internal parasites than grazing species.  Combining that fact with unnatural crowding and artificial feeding in most operations, there are great opportunities for parasite problems.

What can be done to minimize endoparasite problems on game farms and ranches?  One approach is to go back to some fundamental management techniques:

1.  Employ pasture rotation.  Sunlight and grass cutting will reduce the number of infective larva in an empty pasture.  In 30 - 45 days the parasite load should be virtually zero, making this a clean pasture..  Rotating animals continually onto these clean (fallow) pastures means that their worm burden will be reduced with time. 
2. De-worm pregnant females 2-4 weeks prior to giving birth.  This will ensure that their worm burdens are eliminated by the time the offspring arrive.
3. Make every effort to raise newborn animals on parasite-clean pastures.
4. Conduct fecal examinations followed by de-worming at strategic times.  Springtime when green grass is just emerging; September after the summer heat is dissipating; Fall – prior to the first freeze. 
5. Aggregate stool (fecal) samples should be collections of “The Good, The Bad, and The Ugly”.  When collecting aggregate fecal quantities sample the loose stools, the soft stools and the normal appearing stools.  Also consider the size of the fecal droppings.  Young animals that are most susceptible to gastro-intestinal worms will have smaller stool volumes and smaller fecal pellets.  By all means do not leave their samples out of the aggregate fecal collection.
6. Always use systemic anthelmintics in your annual parasite control plan.  This refers to drugs that circulate throughout the animal’s body and kill parasite larvae migrating through its tissues.

I strongly suggest three other diagnostic efforts that can be effectively used in parasite control.  One is called the egg per gram (EPG) count.  This simply counts the number of eggs in a gram of feces and provides a quantitative idea about the severity of the parasite load.  This value is used in another assessment called the fecal egg reduction test (FERT).  In this test epg counts are determined immediately prior to de-worming and 7-10 days after de-worming.  Comparison of these two values is the fecal egg reduction test.  It evaluates the effectiveness of the anthelmintic and the method of delivery into the target animals.  The ultimate test for drug effectiveness is the DrenchriteR  Test.  This is a drug susceptibility test that surveys fecal sample larval survival against three major anthelmintic drug families.  This is the most exact way to evaluate whether a farm or ranch is using the most effective de-wormer.

My final comment should be taken as my most profound instruction:  Work closely with your veterinarian when establishing parasite prevention programs and when treating parasite-related illnesses.  It will save you heartache and money!

Jim Jensen, DVM, DACZM