Grad Student Competition
Does source farm group size affect the performance and behavior of beef calves when commingled at a commercial feedlot?
| Date/Time: |
9/12/2025
08:15
|
| Author: |
Caleb M Brezina |
| Clinic: |
Iowa State University College of Veterinary Medicine |
| City, State, ZIP: |
Boone, IA 50036 |
C.M. Brezina, BSc, DVM
1
;
G.A. Dewell, BSc, DVM, MS, PhD
2
;
R.D. Dewell, BSc, DVM, MS
3
;
R.L. Parsons, BSc, MSc
4
;
A.K. Johnson, BSc, MSc, PhD
5
;
D.B. Haley, BSc, MSc, PhD
6
;
S.T. Millman, BSc, PhD
7
;
1Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA, 50011
2Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA, 50011
3Center for Food Security and Public Health, Iowa State University, Ames, IA, 50011
4Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA, 50011
5Department of Animal Science, Iowa State University, Ames, IA, 50011
6Department of Population Medicine, University of Guelph, ON, Canada N1G 2W1.
Introduction:
Commingling calves from various sources into a single pen is a common practice in the feedlot industry and represents one of the many stressors calves face after leaving their home farm. While current research has focused on whether commingling causes distress, there is growing interest in understanding how the social dynamics within a commingled group may influence calves. Our previous research has shown that the short-term performance of commingled calves who share no common source farm with any pen mates (solitary calves) were more negatively impacted by castration stress compared to commingled calves housed with familiar pen mates from the same home farm. Building on these findings, the objective of this study was to determine if solitary calves’ long-term performance and behavior differed from that of familiar calves in a commercial feedlot and if the group size from their home farm, within a pen, affected these outcomes.
Materials and methods:
300 auction-derived calves (Heifers=200, Steers=100) were purchased and transported to a commercial feedlot; from this population, 200 calves (Steers=50, Heifers=150) were enrolled. Upon arrival, calves were separated by home farm, and treatment groups were created based on home farms. Calves were randomly assigned to 1 of 3 treatment groups and allocated to 1 of 4 pens. Each pen contained 50 calves, with all three treatment groups represented within each pen. One pen of calves were steers, while the other three were heifers. Treatment groups were defined by the percentage of familiar calves in a pen: Large (L) group, where 24 (48%) of the calves present within a pen were familiar; medium-sized (M) group, with 10 (20%) of the calves present within a pen being familiar (to fill a pen, this treatment group was duplicated); Solitary (S) calves, where none (0%) of the calves present within a pen were familiar. Six sentinel calves from each treatment group were randomly selected for data collection. Groups were processed and data was collected on days (D) 0, 14, 85, and 174 after enrollment for average daily gain (ADG), video of squeeze chute behavior (CB), number of vocalizations, serum cortisol, and exit duration (sec). Accelerometer-derived home pen activity was monitored D0 to D14. Number of medical interventions (MI) were monitored from enrollment to slaughter.
Generalized linear mixed models (GLIMMIX) were used to evaluate ADG, exit duration, vocalizations, and MI. A Gaussian distribution was applied for ADG and exit duration, while a Poisson distribution was used for MI and vocalization counts. Day-by-treatment interactions were included in the model, with the individual calf as the subject. Pairwise comparisons were performed for ADG to compare day and treatment. Exit duration was log-transformed to meet normality assumptions. Accelerometer, CB, and cortisol data are under analysis.
Results:
Preliminary results show that there was no observed treatment effect for MI (P = 0.45). S calves had lower ADG on D14 compared to M calves (P = 0.0038), but L calves had no difference between that of either S or M calves (P>0.05). Despite this early advantage, all treatment groups exhibited a reduced ADG on D85 and D174. Exit duration varied over time (P ≤ 0.0001), with the longest duration on D85, with both M calves and S calves taking longer to leave the processing chute. Interestingly, by D174, S calves showed a decrease in exit duration compared to day 85. Vocalizations also differed (P = 0.02), though this was primarily driven by D0 measurements, and no consistent trends were observed by treatment and day after enrollment.
Significance:
Though there was some evidence of short-term effects of treatment by day, where calves assigned to the M groups exhibited ADG benefits compared to L and S calves, there were no long-term ADG differences noted. Further research is needed to discern why M calves seem to have enhanced recovery from arrival stress, and if social bonds are maintained or created amongst treatment groups.
