Case-based workups of sheep & goats (Proceedings)

Article

Please note: this calendar is only designed to serve as an aid in designing a herd/flock health program. Adjustments should be made according to specific animals health needs, production goals and climate.

Sample production calendar

**Please note: this calendar is only designed to serve as an aid in designing a herd/flock health program. Adjustments should be made according to specific animals health needs, production goals and climate.

January

     • BCS females: should be~3/5

     • BCS males: should be ~3/5

     • U/S for pregnancy

     • Booster Chlamydiophila abortus (Chlamydia psittaci)

     • Booster Campylobacter vaccine

     • CDT vaccine - does

     • Evaluate udders

February

     • Parasite program – periparturient rise

     • Delice

     • Nutrition

          o High quality forage

          o Slowly increase grain in females

               • Supplement grain in last 2-4 weeks of gestation or allow access to lush pasture

                    - Increase from 0.5#/head/day to 1.5#/head/day over 2 weeks

               • Plan for 3-4# of good quality hay/head (>10% protein) and 1.5# grain/head/day in late gestation

               • If severe weather, may increase to 2-3# grain/head/day divided into 2 feedings

               • Aim for BCS of 3-3.5/5 at delivery

March – April

     • Kidding/Lambing

          o Dip navels

          o Colostrum

               • 10% of body weight within first 12-24 hours of afe

          o Evaluate udder

          o Castrate, disbud within 1 week of birth

          o I.D.

          o CDT kids/lambs at processing, booster 4 weeks later

     • Dams- 5.5-6# DM/head/day, which includes 1# grain/lamb/day; CP 12-14%

May

     • BCS does

     • Parasite program on adults, deworm lambs/kids

     • Decrease grain

     • Nutrition

          o Turn out onto grass after parasite evaluation

     • Creep feed kids/lambs

          o At 8-12 weeks, should gain 0.3-0.5# daily

          o Crude protein 15%, TDN 54%

          o 0.5-1#/head/day

     • CDT booster lambs/kids - 12 weeks of age

June-July

     • BCS does/ewes ~2.5-3.0/5

August

     • Wean

     • Deworm/coccidiostat to kids

     • CDT vaccine – does

     • Trim feet

     • Cull

          o Teeth, lameness, udders, poor doers, poor breeders, bad testicles

     • Semen test, Brucella ovis test bucks/rams

September

     • BCS does/ewes: 2-3/5

     • BCS bucks/rams: 3-3.5/5

     • Flush does/ewes

          o Best response from BCS 2-3/5

          o Lush pasture or supplement

               • 0.5-1.0#/head/day

          o Flush 2 weeks prior to and 2-3 weeks after turnout

     • Remove bucks/rams from sight, sound, smell of the ewes

     • CAE testing for replacements

     • Vaccinate for C. abortus / Campylobacter 2 w prior to male turnout

October-November

     • Turn out bucks/rams

          o 1:20-25 females

     • Parasite program

     • Remove bucks/rams

December

     • BCS does: 2-2.5/5

Internal parasite program considerations

Haemonchus contortus is the most common target for most small ruminant herds, although Telodorsagia circumcinta, Trichostrongylus axei, Nematodirus spp., Cooperia spp., and coccidia should be considered. Goats, in particular, are very sensitive to internal parasitism and their increasing popularity in the US has led to significant concerns over Haemonchus parasitism and anthelmintic resistance. Most farms I have encountered which have parasitism are severely overstocked and animal husbandry and management must be addressed prior to seeking a "better dewormer." Anthelmintic resistance has been created by drug overuse in suboptimal management situations and in Georgia, 90% of tested farms had worms resistant to ivermectin and albendazole, 30% were resistant to levamisole and 50% of farms that had used moxidectin had resistant worms.

Haemonchus contortus females produce 5000 eggs per day, placing tremendous numbers of infective larvae (developed from eggs in 3 days) on grass daily. Add to this a short life cycle of less than 3 weeks and it's easy to see how rapidly animals can become severely parasitized and that once a resistant population of worms develops, control is difficult.

It is important that we cease total reliance on dewormers to control parasite problems. There is no reason to believe that new classes of dewormers will be developed, making non-drug management and proper drug usage extremely important. Stocking density is an important consideration, but generic recommendations cannot be made, based on variations in climate and forage characteristics. In general, no more than 5-7 sheep or goats should be housed per acre of land. Native grassland and improved pastures which form a dense canopy or are overgrown keep moisture down close to the ground and shade fecal pellets, protecting nematode eggs from dessication and heat destruction. Sparse brush, however, allows heat and air flow around fecal pellets, with temperatures for 155°F recorded in sun-exposed pellets. Rotation of pasture is also important to prevent overgrazing, as the majority of infective larvae are found on grass blades within 2" of the ground. Environmental conditions should also be considered, with rains (0.5-1") producing increases in larval burdens within 2-3 weeks and high heat, as well as low temperatures (<50°F) being unsuitable for larval development. Knowledge of these criteria should guide the use of anthelmintics such that they are only administered when the risk of larval development is high.

The concept of "safe pastures" is important when designing pasture rotation strategies. Safe pastures include pastures which have been harvested, grazed by horses or cattle, or not grazed by small ruminants for 3 months in the warm season and 6 months in the cool season. Intensive pasture rotation is generally performed to maximize forage utilization, but can be extremely useful for parasite control. Rotation schemes ranging from 1 month to 2-3 month patterns have been devised, dependent mostly on climate conditions.

As problems with anthelmintic resistance have been investigated, the concept of individual animal susceptibility has been promoted and serves as the basis for the FAMACHA control scheme. We know that young (first year on pasture) and periparturient animals (-2 to +8 weeks from parturition) have the least resistance to parasitism and have focused deworming on all animals at those times. It is known now that 20% of the animals harbor 80% of the parasites, which leads to the current recommendations that only heavily parasitized animals should be dewormed and animals which are "repeat offenders" should be culled.

Once general herd management has been outlined, determination of efficacious anthelmintics for that premise must occur. There are two main methods for determining which classes of dewormers have retained their efficacy in worm populations. The first is to perform a fecal egg per gram (EPG) test, deworm with the chosen dewormer and then re-run an EPG test 10-14 days later. This Fecal Egg Count Reduction Test will demonstrate a 90% reduction in EPG for efficacious dewormers. Any dewormer without a 90% reduction in EPG has had a reduction in efficacy due to resistant parasites. Samples should be obtained from 10 animals or 10% of each pen, whichever is greater. In large groups, multiple drugs can be tested concurrently by testing 10-15 animals per dewormer. Alternatively, the Drenchrite® larval development assay can be sent to the University of Georgia at an approximate cost of $250. Here, larvae are developed and tested against all available classes of dewormers. This is done on a pooled fecal of 10-20 animals per group and, in some flocks or herds is less expensive than multiple fecals for the fecal egg count reduction test.

After determination of effective dewormers on a given premise, three potential treatment strategies may be considered for implementation. Salvage deworming is based on the fact that 20% of animals host 80% of the parasites and seeks to identify and treat only that 20%. The program validated in the US for this is FAMACHA, and, while it is labor-intensive, it significantly reduces the usage of dewormers, identifies animals with genetic predisposition to parasitism and allows for an increase in worms on the pasture which have not been exposed to dewormers and therefore do not have resistance (refugia). Animals are scored by ocular mucous membrane color (score 1-5) every two weeks based on a color chart purchased from the FAMACHA program. The scores correlate with increasing anemia and only animals scoring 3-5 or 4-5 are dewormed. Animals scoring 1-3 are not treated as long as they appear healthy. Treating only 4s and 5s has been shown to result in the deworming of only 14% of sheep and 31% of goats, significantly reducing deworming use and costs below common "treat all animals on a regular schedule" programs. This should only be used on adult animals due to the reduced body reserves and high susceptibility of young animals. If anthelmintic testing has been done on a herd, deworming anemic animals should be done with the moderately-effective drugs in order to spare the more highly effective drugs for parasite emergency cases. Animals which repeatedly score 4-5 on the FAMACHA score should be culled, resulting in a parasite-resistant population of animals. Tactical deworming seeks to deworm animals when egg production is highest, limiting dewormer usage at times of low parasite concentration. This approach calls for deworming when the EPG count is >1000 in cold seasons or >2000 in warm seasons. This is particularly useful when weather conditions are optimal (10-14 days after rain following a drought) for parasite buildup on pasture. Strategic deworming targets worms in the animal, not in the environment. For most locations which have good, cold winters, deworm ewes/does three weeks prior to the expected birth of the first lamb/kid and then every 3-4 weeks until the last lamb/kid is three weeks old. This approach addresses the periparturient rise of nematode egg production in females. A weakness of this approach is that it leaves little refugia on the ground by treating animals when worms are in the animals and not on the ground, which promotes resistance.

No matter the deworming strategy selected, Smart Drenching guidelines should be used. This set of recommendations seeks to improve efficacy of dewormers when they are used and prevent anthelmintic resistance. Dewormers, with the exception of levamisole and moxidectin should be dosed at twice the cattle dose for the heaviest animal in the group. All products, including injectable products, should only be used orally. Pour-on products should not be used as pour-ons in sheep and goats due to erratic absorption and therefore an effective under-dosing. Products should be placed in pharynx using drenching guns, rather than being placed in the mouth to ensure that the full dose is captured in the rumen. When using benzimidazoles, animals should be held off-feed for 24 hours prior to treatment, assuming animals are healthy enough for this. This decreases the flow rate of digesta, increasing availability and efficacy of the drug. Also, dosing with 2 doses 12 hours apart has been shown to increase the efficacy of benzimidazoles from 50% to 92%. This may also be used for levamisole, but doses should be separated by 24 hours. It is also useful to hold animals in a working pen for 24 hours after deworming before placing them on a new pasture.

One of the greatest departures from traditional thinking has been the discovery that rotating dewormers regularly speeds resistance rather than avoiding it. The current recommendation is that an effective dewormer be used until resistance to that dewormer is documented and then a new drug initiated, again with proper attention to good management practices. Newly purchased animals should be cleared of internal parasites before introduction to new herd. It is recommended that these animals be quarantined and have a EPG count done, held off feed for 24 hours, then dewormed with moxidectin, levamisole and albendazole on the same day. Fourteen days later, a repeated EPG count should be zero and then the animal should be placed on a contaminated pasture, as any surviving worms will be triple-drug-resistant and there will be no refugia on any clean pasture.

Other potential parasite-control mechanisms are being investigated, including Sericea lespedeza, which has concentrated tannins and suppress internal parasites, nematode trapping fungi (D. flagrans), copper oxide wires (risk of copper toxicity), breed selection, nutritional support with specific attention to protein, phosphorus, cobalt, copper and molybdenum, and parasite vaccines.

References available upon request.

Related Videos
Related Content
© 2024 MJH Life Sciences

All rights reserved.