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Demonstrating the effect of using Strategic Deworming and the prevalence of Parasite Resistance in Saskatchewan Background Cattle

By Naomi Paley, BSA, PAg, Regional Livestock Specialist, Saskatchewan Ministry of Agriculture 

In response to new research on parasite resistance in Western Canadian beef cattle, the Ministry of Agriculture Livestock Specialists, in partnership with Merck Animal Health, identified the need to examine and demonstrate the prevalence of parasite resistance and the effect of using a strategic deworming program in three Saskatchewan backgrounding lots.

Introduction

Pour-on dewormers have been a mainstay in the North American cattle industry for over 25 years. Because they can be inconsistently absorbed in the bloodstream, they can lead to reduced levels of active ingredients being delivered to the parasitic infection in the stomach and intestinal tract. Parasites that survive these treatments not only continue to produce eggs that are shed back on pasture, but they and their offspring are also more likely to become resistant to the compounds to which they have been exposed.1 Because the compounds used in these and some other types of dewormers are in the same drug class (macrolytic lactones) and have a similar mode of action, the potential for the development of parasite resistance is a growing concern.

The introduction of deworming products containing fenbendazole in recent years has provided a new tool for producers to combat parasite resistance to macrocyclic lactone (ivermectin) dewormers.  This new technology has not been widely adopted by beef cattle producers due to a lack of awareness that parasite resistance is a growing problem in Western Canada. 

A study at the University of Calgary’s Faculty of Veterinary Medicine showed that parasite resistance to ivermectin is becoming increasingly common in Western Canada. They reported that Ivermectin is no longer guaranteed to remove all roundworms from Canadian cattle with approximately 30 to 60 per cent of herds showing sub-optimal efficacy.2

Parasitic worms cost the North American cattle industry about $2 billion per year.3 Even with 70 per cent of producers using an ivermectin dewormer on calves in the fall, there are subclinical production losses that occur due to parasite resistance. 4

After three years of trials at the Western Beef Development Centre, Merck Animal Health reported that using Safe-Guard in a strategic deworming plan in the spring on cow-calf pairs significantly reduced parasite loads compared to the control group that used a single treatment of a generic ivermectin pour-on in the fall.  They reported a net return of $22.37/calf in their strategically dewormed group.5

Objective:

The primary objective of this project was to demonstrate the economic and production benefits of using a strategic deworming program containing fenbendazole (Safe-Guard) and to determine the prevalence of parasite resistance in three Saskatchewan backgrounding operations. 

Trial Design:

  • Three Saskatchewan backgrounding operations were set as demonstration locations for this project. 
  • Two pens of backgrounding cattle were used at each of three locations and one pen was assigned as a treatment group. The control group of calves was treated with ivemectin pour-on and the treatment group was treated with ivermectin pour-on and Safe-Guard Suspension 10 per cent oral drench (2.3 ml/100 lbs.) 
  • Each of the three backgrounding lots had differing feed rations and management parameters from the others. However, the calves in both the control and treatment groups at each lot were fed the same ration and had the same management parameters over the course of the demonstration period.
  • Fecal samples* from 20 animals in each group were taken prior to treatment to determine parasitic worm load prior to a deworming treatment. Both groups received their deworming treatment(s) during routine processing upon their entry to the backgrounding lot.
  • A second round of fecal samples (20 per group) was taken approximately two weeks after treatment to determine the efficacy of each deworming treatment.
  • All samples underwent fecal egg count reduction (FECR) tests. The FECR is the most widely used method to assess the efficacy of anthelmintics (antiparasitic drugs) against gastrointestinal strongyles. This test provides an estimation of anthelmintic efficacy by comparing worm egg counts from hosts treated or not, before and after treatment and thus evaluating FECR.
  • Animals in both groups were weighed upon entry to the pen and again approximately 110 days later to demonstrate any effects on weight gain and performance.
  • A cost analysis was done to determine if there was an economic benefit to using the Safe-Guard dewormer as part of the deworming strategy.

Results:

Calves in this demonstration trial were born in the spring of 2016 and were turned out to summer pasture with their dams. About 90 to 95 per cent of the parasite population exists in the pasture.6 In the spring, this parasite population consists of infective worm larvae that have survived the winter and lie in wait on pasture. These calves would have acquired a patent infection of parasites while on spring pasture with their dams.

Table 1.  Interpretation of Fecal Worm Egg Counts

Modified Wisconsin Sugar Flotation Techique7

ANIMAL TYPE

LOW

MODERATE

HIGH

Calves

10 or less

10 - 50

>50

The deworming products reduced the fecal egg counts in all cattle lots but the pens that received Safe-Guard had a more consistent trend. The level of FECR depended on the lot and the deworming product (P = 0.006). The calves in lots two and three had moderate to high levels of fecal egg counts prior to treatment, while the calves in lot one had low counts. This variability can be attributed to differences in pasture contamination at each of the locations and the deworming control measures in past years.

Lots one and three showed a FECR of about 75 per cent with the control group while lot two only showed a 30 per cent FECR. Lot two also had the highest initial fecal egg counts prior to deworming.  

All three lots showed significant FECR with Safe-Guard, with lots one and two near or at 100 per cent and lot three at 96 per cent.

Table 2.  Fecal Egg Counts (eggs/3 grams) and Fecal Egg Reductions in background lot

Trial Day

 

Control

 

Treatment

 

LOT #1

Day 0

Induction Treatment

7.1 (Low)

6.65 (Low)

Day 16

Post Treatment

1.7 (Low)

0 (Low)

 

Fecal Egg Count Reduction (FECR)

76.0%

 

100.0%

 

LOT #2

Day 0

Induction Treatment

40.65 (Moderate)

54.9 (High)

Day 14

Post Treatment

28.4 (Moderate)

0.1 (Low)

 

Fecal Egg Count Reduction (FECR)

30.10%

 

99.82%

 

LOT #3

Day 0

Induction Treatment

13 (Moderate)

14.25 (Moderate)

Day 41

Post Treatment

4.05 (Low)

0.55 (Low)

 

Fecal Egg Count Reduction (FECR)

74.70%

 

96.14%

 

There was no effect (P >0.31) of lot or treatment on the total initial/final body weight, but there were significant differences in average daily gains due to the dependence
(P = 0.03) between lots and treatment. For example (as shown in Table 3), even though there were significant differences in average daily gain (ADG) for lot one (P=0.02) and lot three (P = 0.03), lot two indicated a trend (P = 0.06). In general, calves in the treatment groups gained an average of 15.14 lb. (6.87 kg) more than those in the control group.

Table 3.  Background Lot Performance - Control vs Treatment

Control

Treatment

Pvalue

LOT #1

Number

47

46

-

Initial Weight (lb)

566.43

588.17

NS

Final Weight (lb)

720.17

764.95

NS

Gain

153.74

176.78

-

Days on Feed

82

82

-

Average Daily Gain

1.86

2.14

0.022

LOT #2

Number

70

67

-

Initial Weight (lb)

581.07

577.50

NS

Final Weight (lb)

830.50

837.16

NS

Gain

249.43

259.66

-

Days on Feed

101

101

-

Average Daily Gain

2.45

2.55

0.061

LOT #3

Number

178

154

-

Initial Weight (lb)

526.97

525.28

NS

Final Weight (lb)

676.98

687.43

NS

Gain

150.01

162.15

-

Days on Feed

72

72

-

Average Daily Gain

1.89

2.07

0.025

Economics:

Based on Saskatchewan feeder cattle prices (CanFax: March 3, 2017, Issue 9):

  • The average price for 600 to 800 lb. (272 to 363 kg) to feeder cattle was $177.13/cwt. The average value of calves in the ivermectin control group was $1,314.97 and those in the Safe-Guard treatment group had an average value of $1,351.80.
  • The cost for the Safe-Guard Suspension product was $3/head. The net return to using the Safe-Guard treatment as part of a deworming strategy in this demonstration was $33.83/head.

Producer Feedback:

  • Overall the producers at each of the three background lots were satisfied with the improved performance provided by using the Safe-Guard deworming strategy.
  • Two of the three lots processed and treated calves during colder weather when temperatures were well below -15 C. As the Safe-Guard oral suspension is a water-based product, it is subject to freezing. This made it necessary to use an insulated bag with a warming device to keep the product flowing.  
  • The producers also indicated that the extra time and labour to administer the oral suspension product when several other vaccinations and procedures are taking place added some extra time to processing.
  • These producers indicated that they would prefer to use the Safe-Guard Premix in the feed to alleviate these issues with the oral suspension.

References:

  1. Bliss DH, Moore RD, Kvasnicka WG, “Parasite Resisitance in U.S. Cattle.”  The AABP Proceedings (2008)
  2. Avramenko RW, Redman EM, Lewis R, Bichuette MA, Palmeira BM, Yazwinski TA, Gilleard JS. “The use of nemabiome metabarcoding to explore gastro-intestinal nematode species diversity and anthelmintic treatment effectiveness in beef calves.”  Int J Parasitol. 2017 Aug 7
  3. Stromberg BE, Gasbarre LC. “Gastrointestinal nematode control programs with an emphasis on cattle.” Vet Clin North Am Food Anim Pract. 2006 Nov;22(3):543-65.
  4. Windeyer C, “Calf Management Survey.” 2015
  5. Merck Animal Health. “Determination of the economic benefit of a Strategic Deworming combined with an Anabolic Implant Program for Cow/Calf operations in western Canada.” Reference study number 41-AH90-SGRA-M-2014
  6. Stromberg BE and Averbeck GA. What’s New for Parasite Control in Cattle.  Minnesota Dairy Health Conference (1988).  Retrieved from the University of Minnesota Digital Conservancy. http://purl.umn.edu/117341.
  7. Bliss D, Veterinary Consultants Guide for: The Interpretation of Fecal Worm Egg Counts Using “The Modified Wisconsin Sugar Flotation Technique.” www.midamericaagresearch.net
*Fecal analysis provided courtesy of Merck Animal Health at BioCheck Veterinary Diagnostic Lab, Lethbridge, AB.

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