Stanton PhD Thesis final_docx - Atrium - University of Guelph

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States were administering an injectable antimicrobial metaphylactically to all cattle for the prevention of respiratory disease (USDA, 2000). A meta-analysis of field trials indicated that for feedlot calves, administration of oxytetracycline or tilmicosin on the day of arrival at the feedlot consistently reduced morbidity rates attributable to BRD (Van Donkersgoed et al., 1993). The movement of beef cattle into a feedlot is comparable to the movement of dairy calves from individual to group housing. In both cases, calves experience similar stressors, which include nutritional, environmental and social changes, transportation, and increased pathogen exposure. Regardless of the method used to administer antibiotics, this practice must be carefully evaluated by both researchers and producers to maximize efficacy and avoid unnecessary use given the concern over developing antimicrobial resistance. The ideal circumstances for adopting this prophylactic program are the following: a targeted disease that is highly contagious and is endemic to the region, successful clinical treatment is difficult, and the risk of pathogen exposure is constrained within a short time period. In conjunction with this method, efforts should be made to reduce or minimize manageable risk factors with the goal of reducing or eliminating the need for prophylactic use. For this program to be most effective good record keeping is essential in order to review historical disease trends to identify high risk time periods and environmental triggers. In addition, these records are needed for outcome assessment to measure the success of this program and other management changes made to decrease the risk of disease for efficacy. 1.6 LONG-TERM IMPACTS OF BOVINE RESPIRATORY DISEASE COMPLEX BRD is a complex of disease processes most commonly resulting from infection with various microorganisms, including Pasteurella multocida, Mannheimia haemolytica and Mycoplasma bovis, Histophilus somni in conjunction with bovine herpesvirus-1 (BHV-1) bovine 21
viral diarrhea virus (BVDV) bovine respiratory syncytial virus (BRSV) and parainfluenza 3 virus (PI3V) (Kahn, 2005). The development of BRD is typically initiated by an environmental stressor and viral infection, which weakens the resistance mechanisms of the lungs and allows bacterial colonization (Yates, 1984). There are many factors that have been associated with increased risk of BRD, including mixing of animals, transportation, light weight or younger animals within a group and persistent infection with BVDV (as reviewed by Taylor et al., 2010). The National Animal Health Monitoring Survey (NAHMS) dairy heifer study found that 6% of weaned dairy heifers were treated in 2007 for respiratory disease (USDA, 2009). However, the NAHMS study defined post-weaned heifers as including all animals from weaning to first calving. The wide age variation encompassed by this definition would include many older animals that were at low risk of BRD. Other epidemiologic studies in North America have reported BRD rates in milk fed dairy calves ranging from 0.1 cases/100 days in Minnesota (Sivula et al., 1996), 25% of calves in New York State (Virtala et al., 1996) and 39% of calves in Saskatchewan (Van Donkersgoed et al., 1993). This substantial variation in the reported rates of disease probably results from a combination of the differences in the diagnostic criteria used, disease definition, age of the calves, the composition of the viral and bacterial agents, and management conditions. Costs of BRD were estimated at $14.71(range: 0 - $119) per pre-weaned calf per year and $1.95 (range: 0-$9.25) per weaned dairy calf stock per year by Michigan producers in 1990 (Kaneene and Hurd, 1990). These costs included labor for detection and treatment of disease, drugs, veterinary fees and cost to replace animals that are died as a result of clinical disease. The higher cost observed in young calves is based on the timing of preventive practices, which 22
Page 1 and 2: AN EVALUATION OF THE IMPACT OF MANA
Page 3 and 4: differences in weight gain or calf
Page 5 and 6: 3.2.2 Experimental Study Design 68
Page 7 and 8: 7.4.5 Culling and mortality prior t
Page 9 and 10: Table 6.5: Reasons for death loss a
Page 11 and 12: and season as fixed effects and for
Page 13 and 14: , which requires that “all calves
Page 15 and 16: ehaviour of dams challenged with LP
Page 17 and 18: In cattle, early disease detection
Page 19 and 20: increased rest and decreased appeti
Page 21 and 22: 1.4.2 Nutritional Stressors Dairy c
Page 23 and 24: humans, the metabolic rate increase
Page 25 and 26: Without human intervention, calves
Page 27 and 28: average group size of three or four
Page 29 and 30: al., 2004). Group composition and g
Page 31: first is the addition of antibiotic
Page 35 and 36: 1.7 CONCLUSION AND THESIS OBJECTIVE
Page 37 and 38: Buhman, M. J., L. J. Perino, M. L.
Page 39 and 40: Hemsworth, P. H., G. J. Coleman, J.
Page 41 and 42: Schein, M. W. and M. H. Fohrman. 19
Page 43 and 44: Waltner-Toews, D., S. W. Martin and
Page 45 and 46: ehavioural observations ( Borderas,
Page 47 and 48: and had access to ad libitum calf s
Page 49 and 50: may indicate abdominal discomfort,
Page 51 and 52: identified in 5% (40/788) of calves
Page 53 and 54: of diarrhea in calves on this farm
Page 55 and 56: The most common response to the vig
Page 57 and 58: at any observation period. For this
Page 59 and 60: 3 was associated with lower ADG rel
Page 61 and 62: of heifers to allow them to calve a
Page 63 and 64: 2.5 REFERENCES Al-Chaer, E. D. & Tr
Page 65 and 66: Panivivat, R., Kegley, E. B., Penni
Page 67 and 68: Table 2.2: List of exclusions used
Page 69 and 70: Table 2.4: The lsmeans ± S.E. of t
Page 71 and 72: Figure 2.1: Timeline describing tri
Page 73 and 74: Proportion of calves performing beh
Page 75 and 76: in a lower rate of vocalizations an
Page 77 and 78: sites. During the summer months bot
Page 79 and 80: treatment and weight gain category.
Page 81 and 82: pre-weaning calf starter intake, an
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Calves spent a total of 13 ± 6 (me
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calves were still allowed access to
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It was hypothesized that the more t
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calves to consume sufficient calf s
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Table 3.1: Descriptive list of obse
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Number of steps per day 7000 6000 5
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Number of lying bouts per day 35 30
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Weight gain (kgs) first 7 days post
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The concept of separating stressors
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were bedded with straw. While house
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4.2.5 Data Collection Calf starter
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4.3 RESULTS enrolment. On average,
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4.3 DISCUSSION There was no effect
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4.4 REFERENCES Chua, B., E. Coenen,
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Steps per day 2500 2000 1500 1000 5
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Appendix 4.1: Scoring sheet used fo
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positive for M. bovis and 4 differe
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feedlots (Van Donkersgoed, 1992). I
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protocol included the identificatio
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(cases) and two calves closest in a
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No statistical analysis was perform
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5.4.3 Growth Three calves returned
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5.4.4 Testing for Mycoplasma Of the
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may be an early sign of respiratory
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small number of unilateral ear droo
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evaluated for efficacy and carefull
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5.6 REFERENCES Biddle, M. K., L. K.
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USDA. 2007. Dairy 2007, part II: Ch
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Table 5.2: Incidence and median age
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Table 5.4: Breakdown of the number
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Figure 5. 5.1: 1: Images taken from
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6.1 ABSTRACT Bovine respiratory dis
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efore entry into the milking herd o
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with bovine viral diarrhea (BVD). O
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6.3.3 Outcome Measures All calves w
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tests, or multiple partial F-tests,
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The effect of treatment on height a
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this study involved continuing with
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is important to emphasize that the
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6.7 REFERENCES J. Carroll and N.E.
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Table 6.1: Disease variables consid
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Table 6.3: Least squares means ( ±
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Table 6.5: Reasons for death loss a
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CHAPTER 7: THE IMPACT OF BOVINE RES
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7.2 INTRODUCTION Bovine respiratory
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days following study enrolment than
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Age at First Calving Since age at f
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(Weaning, Transition, Grower 1, Gro
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The excluded source farm resulted i
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of calves with BRD60 survived to fi
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7.4.8 Milk Production First Test Da
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BRD before 6 months of age decrease
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BRD following movement to group hou
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calves with BRD60 were 1.5 (95% CI:
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7.7 REFERENCES Correa, M. T., C. R.
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Table 7.1: Calving Ease Scoring Sys
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Table 7.3: Least-square means (± S
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Table 7.5: Proportion of calves sur
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Table 7.7: Producers primary reason
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Table 7.9: Effect of BRD60 on calvi
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Table 7.11: Distribution of heifers
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Figure 7.2: Difference in least squ
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Figure 7.4: Time to event analysis
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CHAPTER 8: CONCLUSIONS AND FUTURE R
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Heifers with poor post-weaning grow
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strategic antimicrobial use was met
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Specifically, How can disease sever
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Does transportation, initial social
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