Stanton PhD Thesis final_docx - Atrium - University of Guelph

the management of heifers recovering from BRD, there is a need to determine which factors
impair their growth. There are four hypotheses for this decreased weight gain observed in heifers
with BRD after recovery from clinical disease;
1) decreased feed efficiency,
2) decreased feed intake,
3) fewer, shorter feeding bouts,
4) more displacements at the feed bunk.
Each of these hypotheses should be tested at different stocking densities and social
mixing to determine if BRD heifers at high stocking densities show greater reductions in feed
efficiency and intake, greater alterations in feeding behavior, and more feed bunk displacements
relative to healthy heifers and to BRD heifers housed at lower stocker density.
If the outcomes of feeding behavior or feed efficiency are altered by stocking density,
there is a potential to alter the management of dairy calves during convalesce based on this
knowledge. The impact of different proportions of calves with a prior history of BRD within a
group on disease spread, relapse rates and growth was recently investigated at a commercial
heifer rearing facility in Spain (Bach et al., 2011). These researchers did not find a difference in
ADG depending on group composition. However, their analysis was completed at the pen level,
and using a small sample size. Further research to determine the impact of group composition on
the growth of sick calves would be beneficial to identify improved methods of managing animals
during convalescence.
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