Stanton PhD Thesis final_docx - Atrium - University of Guelph

and movement to a novel environment was associated with increased steps and decreased lying
time. If mixing and movement to a novel environment occurred a week apart the increase in the
number of steps and the decrease in lying time was reduced compared to mixing and movement
occurring simultaneously. Further research in needed to determine if the decreased activity in the
novel environment performed by pre-mixed calves was a result of decreases agonistic behaviours
or if the agonistic behaviours occurred whenever calves were mixed. This information would
determine if premixing calves reduces the stress associated with movement to a novel
environment. Further study of this management procedure would be valuable to identify the
types of behaviors occurring upon movement to a novel environment and determine the effect of
increased transportation stress and grouping on adaptation to a novel environment and the risk of
disease.
A second approach, which can be used in conjunction with minimizing weaning stress, is
the strategic use of antibiotics at the group level. The primary criteria for consideration of this
approach were the use of antibiotics during a short time period of high risk of disease that cannot
be eliminated through other methods, and the welfare impacts of disease, particularly when
recovery is poor or prolonged. Prophylactic antimicrobial use was reviewed based on its
established efficacy in beef feedlots and its previously unstudied use in dairy calves. Two time
periods were evaluated; the first was shortly after birth when calves arrived at a heifer raising
facility and the second was upon first movement to group housing following weaning.
Prophylactic antimicrobial use reduced disease in both populations. For dairy calves that
received a long acting antibiotic upon arrival at a heifer raising facility, the incidence of otitis
and diarrhea were reduced in the first 8 weeks of life. For this reason, the efficacy criterion for
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