Sergio Lasso Ramirez | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Sergio Lasso Ramirez. This seminar is open to the general public to attend.

MSc with Dr. Gleise Madeiros da Silva

Zoom Link: https://ualberta-ca.zoom.us/j/91532243371?pwd%3DsVjon2Hk7oanlmnSajfEWJTle6bOmC.1

Thesis Topic: Influence of growth implants on beef calf immunity and growth

Abstract: 

Growth implants have been widely used in beef production systems to improve growth performance without compromising animal welfare and health status. However, the effect of growth implants on the health status and vaccine response of suckling and weaned calves has not been deeply analyzed. Therefore, these studies aimed to evaluate the growth performance and immunity of beef steers under different hormonal implant strategies and the timing of booster vaccination.

In experiment 1, ninety crossbreed beef calves were blocked by age, stratified by birth BW, and assigned (30 per treatment) to one of three treatments in a completely randomized block design: 1) Synovex C (SC), 2) Synovex One Grower (SG); or 3) no implant (CON). After implantation until weaning, all calves were raised alongside their dams in a single pasture and vaccinated on d 0 and d 94 against BRD. Calves were allocated to a single pen at weaning and received a total mixed ration ad libitum until d 60 post-weaning. Body weight and blood samples were collected to analyze insulin-like growth factor (IGF-1), cortisol, and β-hydroxybutyric acid (BHBA), serum antibody titers and complete blood cell count. In experiment 2, fifty-nine crossbreed beef calves were stratified by birth BW and age and randomly assigned in a split-plot design with the same implant treatment described in experiment 1 as the main plot and timing of vaccination as the subplot with the timing of booster vaccination at weaning (WV) or 7-d post-weaning (PWV). Calves received ad libitum hay from weaning until d 63 post-weaning. Body weight and blood were collected to perform the same analyses as in experiment 1, plus non-esterified fatty acids and leptin.

In experiment 1, infectious bovine rhinotracheitis (IBR) titers were greater (P = 0.022) in SG compared to SC and CON (16.3 vs 12.7, and 13.3 ± 0.45) while IGF-1 was greater (P = 0.045) in SC and SG compared to CON (119.9 and 111.1 vs 99.1 ± 6.60 ng/mL). Pre-weaning average daily gain (ADG) was greater (P = 0.01) in SG compared to CON, while SC was intermediate (1.18, 1.04, 1.12 ± 0.03 kg, respectively); from d 94 to 154 greater (P = 0.03) in SG and SC compared to CON (1.52 and 1.50 vs. 1.37 ± 0.07 kg). In experiment 2, a treatment × timing of booster vaccination interaction (P = 0.003) was observed with greater monocyte counts in SG-PWV compared to SC-PWV and CON-PWV (0.40 vs. 0.16 and 0.07 ± 0.02 109cells/L). A timing of booster vaccination × day interaction (P = 0.01) was observed for cortisol with lower concentration in WV compared with PWV on d 0 a 28 (82.0 vs. 35.9 and 107.0 vs. 32.7 ± 2.745 ng/mL respectively). Greater BW (P = 0.049) was observed in SG compared to CON, while SC was intermediate on d 28 (238, 232 and 225 ± 3.59 kg, respectively) and d 35 (230, 228 and 225 ± 3.59 kg, respectively; P = 0.049). In summary, growth hormonal implants enhance growth performance, with SG showing the best response. The first study evidenced that SG enhanced the immune response to the IBR vaccine. The second study found that hormonal implants were associated with reduced leptin levels, increased IGF-1, and fewer lymphocytes, suggesting a reduction in catabolic stress effects.